Hot Science is a series exploring the cutting edge of science and technology. With topics from big data to rewilding, dark matter to gene editing, these are books for popular science readers who like to go that little bit deeper …

AVAILABLE NOW AND COMING SOON:

Destination Mars:
The Story of Our Quest to Conquer the Red Planet

Big Data:
How the Information Revolution is Transforming Our Lives

Gravitational Waves:
How Einstein’s Spacetime Ripples Reveal the Secrets of the Universe

The Graphene Revolution:
The Weird Science of the Ultrathin

CERN and the Higgs Boson:
The Global Quest for the Building Blocks of Reality

Cosmic Impact:
Understanding the Threat to Earth from Asteroids and Comets

Artificial Intelligence:
Modern Magic or Dangerous Future?

Astrobiology:
The Search for Life Elsewhere in the Universe

Dark Matter & Dark Energy:
The Hidden 95% of the Universe

Outbreaks & Epidemics:
Battling Infection From Measles to Coronavirus

Rewilding:
The Radical New Science of Ecological Recovery

Hacking the Code of Life:
How Gene Editing Will Rewrite Our Futures

Origins of the Universe:
The Cosmic Microwave Background and the Search for Quantum Gravity

Behavioural Economics:
Psychology, Neuroscience, and the Human Side of Economics

Hot Science series editor: Brian Clegg

ABOUT THE AUTHORS

Paul Jepson is Nature Recovery Lead with Ecosulis Ltd and was until recently a director of Oxford University’s MSc course in Biodiversity, Conservation and Management. He has published several scientific and popular articles on rewilding policy and action philosophy, and is a regular contributor to TV and radio. He is currently a member of Rewilding Europe’s supervisory board.

Cain Blythe is Managing Director of Ecosulis Ltd and specialises in habitat restoration, particularly through the adoption of natural regeneration techniques, nature recovery and the use of technology in conservation. He is currently contributing to a number of monitoring trials relating to beaver releases in England and Wales.

ACKNOWLEDGEMENTS

This book is inspired and informed by the many rewilding practitioners and progressive scientists we have met over the years, and by the enthusiasm and contributions of young conservationists seeking to shape a more hopeful and ambitious approach for conservation in the 21st century. In particular we would like to thank Wouter Helmer, Richard Ladle, Marc Macias-Fauria, Yadvinder Malhi, Christopher Sandom, Frans Schepers, Jens-Christian Svenning, Frans Vera, Charlie Burrell, Daniel Allen, Alan Feest and Sara King for the many stimulating conversations and field visits over the years. Our special thanks to Wouter Helmer and Richard Ladle for reviewing full drafts of the book and to our wives, Susanne Schmitt and Emily Blythe, for their support and many constructive inputs to draft chapters.

Lastly, we hope that this book will help provide an overview of the science that underpins the idea of rewilding and encourage readers to contribute in whatever way they can to the shaping of this new and ambitious conservation agenda.

CONTENTS

Title Page

About the Authors

Acknowledgements

1 New horizons

2 Megafauna pasts

3 Downgrading our planet

4 Rewilding’s practical origins

5 Wild nature – cascades, spaces, networks and engineers

6 Earth system impacts

7 Rewilding politics and ethics

8 Scaling up rewilding

9 Rewilding – ten predictions for the future

Further reading

Index

Copyright

1

NEW HORIZONS

This century is witnessing a fundamental reassessment of the science and practice of nature conservation. An exciting and unsettling body of new thinking is emerging, inspired by the realisation that we have internalised ecological impoverishment in our science, culture and institutions. This impoverishment is a consequence of the syndrome of ‘shifting baselines’, where each generation assumes the nature they experienced in their youth to be normal and unwittingly accepts the declines and damage of the generations before.

A generation ago, at the time of the 1992 Rio Earth summit, ecologists and conservation biologists succeeded in raising the fate of biodiversity to the top of the environmental policy agenda. Their science was rooted in the comparative traditions of natural history and the ecology of communities of species and strongly influenced by the protectionist worldviews of 1970s environmentalism. A focus on the components of nature – species, sites and habitats – translated into clear and powerful law and policy aimed at protecting nature from the wounding ways of humanity. Framing nature as units or components enabled biodiversity targets to be set, and the development of an empirical and international conservation science.

The science of biodiversity, and the institutions it spawned, assumed that the ecosystems that were present at the beginning of the industrial era represented the natural baselines that should be conserved. Indeed, at this time it was considered appropriate that such baselines provided the foundations upon which biodiversity was to be protected and measured. This made intuitive sense as, after all, the tropical rainforests, African savannas and pastoral landscapes of Europe all supported diverse and flourishing natures that were disappearing fast in a globalising world, characterised by increasing population and resource demands.

By the turn of the millennium, biodiversity science had become accomplished and influential. But, like progressive rock in the 1970s, it has also become a little self-serving and out of touch with trends in science and wider society. In particular, the relentless telling of stories of biodiversity decline and an impending sixth-extinction crisis, combined with newer anxieties over climate change, has led to a growing sense of despondency within the conservation movement. Many have started to lose hope and question whether they still want to devote their lives and careers to lessening harm and fruitlessly cataloguing the end of nature.

Then in 2005 and 2006 the prestigious journals Science and The American Naturalist published papers proposing audacious new agendas for conservation science. In the first, titled ‘Pleistocene Park: return of the mammoth’s ecosystem’, Sergey Zimov pointed out that up until 10,000 years ago, much of the Arctic was covered by steppe grasslands, created and maintained by vast herds of mega-herbivores. He argued that their disappearance could be attributed to human hunting pressure, and that the mammoth steppe ecosystem can and should be restored as a strategy to reduce carbon emissions from the thawing yedoma (permafrost) soils. The second paper, authored by a group of US conservation scientists led by Josh Donlan, was ‘Pleistocene Rewilding: an optimistic agenda for twenty-first century conservation’. This group pointed out that assemblies of large vertebrates produce complex food webs, and that continental-scale declines of megafauna over the millennia have resulted in downgrading of nature. They outlined an agenda to restore ecological functions through the reassembly of the remaining large herbivore guilds,* such as elk, bison, and feral horses – and even introduced species from different faunal regions, such as camels. The belief was that such surviving wild herbivores could ‘do the ecological job’ of lost species and that this ‘rewilding’ was a better alternative than doing nothing or relying on the ageing and failing protectionist approach of the 1970s.

To continue the music analogy, it was as if punk rock had hit the conservation science scene. The agendas introduced in these papers were brash, energising, novel and controversial. They signified a desire to shake up the present but also expressed an ambition to shape a new and inspiring future. The Pleistocene rewilding concept was robustly criticised by some in the conservation establishment, who accused the authors of opening a Pandora’s box and proposing the creation of ‘Frankenstein ecosystems’. Yet, the arguments in both papers gave new expression to a scientific riff called ‘functionalism’ which has subsequently become the scientific basis of rewilding practice.

A functionalist approach focuses on the connections between the biological and physical components of an ecosystem and the properties that emerge from these relationships. It takes its lead from Charles Darwin’s evolutionary theory and the insight that interactions between organisms and their environment drive the evolution of physical and behaviour traits, for example large body size or secretive behaviours to avoid predation, or spines and thorns as protection against browsing. However, functional ecology goes beyond evolutionary biology and seeks to understand the role of different ecosystem components in the creation of flows of energy, water, gases, nutrients and organisms – the processes that are vital to the functioning of an ecosystem.

Although from different cultures and continents, Zimov and Dolan and colleagues were making the same point, namely that megafauna play a disproportionate role in the functioning of ecosystems, and that it is time for conservation to expand its horizons and restore such ‘functional’ species whose presence generates ripples of ecological interactions – and to allow these interactions, rather than human interventions, to steer the future trajectory of natural systems.

Since 2005, there has been an explosion of scientific and popular articles on rewilding. However, early in 2019, an international group of scientists published a paper arguing that the term has become fuzzy and should be abandoned because it lacks the precision necessary for robust scientific analysis. This view, while understandable, misses the fact that rewilding is already being applied to, and adopted by, pioneering conservation initiatives in different contexts and continents. These projects differ in their degree of innovation, but all emphasise the restoration of ecological functions and encourage a better understanding of the processes, dynamics and connectivity of ecosystems.

In this book we will explore these ideas further. We will also provide an understanding of the interactions between new insights from ecology and pioneering rewilding projects and how this is leading to the formation of powerful conservation agendas and movements. We use the word ‘interaction’ deliberately because rewilding also signifies a promising new dialogue between scientists and networks of grounded conservation professionals who are coming together to drive innovation in ecological recovery and societal change.

Self-willed nature

In order to understand the potential of rewilding and its argument for multiple biodiversity baselines we will, in the next chapter, delve back into the Pleistocene era with its roaming aurochs, mammoths and prowling sabre-toothed tigers. But, before exploring the vibrant ecological pasts that paint the scene for possible multicoloured futures, we will give a brief history of rewilding and reveal the thinking of its original proponents.

The term rewilding was coined in the mid-1990s by a group of US conservation biologists, led by Dave Foreman and influenced by wilderness and deep ecology philosophy. They presented rewilding as a continental-scale agenda to restore self-regulating land communities through the creation of large wilderness complexes and supporting populations of top predators (notably wolves in Yellowstone national park) that reassert top-down trophic controls.† This has become known as the 3Cs (cores, corridors and carnivores) model of rewilding. Independently, the Dutch embarked on a radical new conservation restoration agenda during the 1980s termed ‘nature development’. This had similarities to the US rewilding agenda, specifically the creation of an ecological network to connect remaining natural areas and the aspiration for ‘self-willed’ natures – ecological systems that would function and evolve without the constant intensive management required in many European reserves.

The policy of nature development was catalysed by a radical public experiment in nature restoration at the Oostvaardersplassen (OVP), located about 20 miles to the north-east of Amsterdam. It was conceived by a group of progressive ecologists within the Dutch nature conservation agency Staatsbosbeheer, led by Frans Vera. Individuals such as Vera broke away from the more traditional ecological models, such as those relating to ‘climax’ vegetation developed by Frederic Clements in 1936 (see p. 32). Driven by a tailwind of widespread biodiversity decline, Vera and his colleagues sought new ways to re-establish nature, and on a larger scale and with greater ambition than previously seen in Europe. The OVP experiment involved the reassembly of a guild of large herbivores, including ‘wilded’ horses and cattle and red deer, to create a Serengeti-like landscape. The results were startling – populations of birds and small mammals rebounded but also exhibited ‘boom and bust’ cycles on the reserve that caused species to disperse into the wider landscape. The novel OVP ecosystem challenged foundational tenets of ecological science and the belief that the ‘natural’ vegetation of Europe is closed-canopy forest. It became a magnet for nature-minded people seeking a practical demonstration of rewilding ideas – and we will discuss its origins and significance in detail in Chapter 3. However, the OVP also provoked controversy from farmers and citizens who believed that allowing cattle and ponies to starve in hard winters is cruel and unjustifiable.

As a result, this European version of rewilding is generally regarded as even more radical and unsettling than the original US model. It is producing natures that are novel from both an ecological and cultural perspective and that are out of alignment with established law, policy and social norms. The natural ‘cycle of life’ disappeared from the everyday experiences of most Europeans long ago, and over time a set of binaries have shaped and ordered European landscapes, imaginations and institutions. These binaries include wild–domestic, natural–cultivated and humane–inhumane. European rewilding unsettles and blurs these boundaries, and this makes it political and potentially transformative.

Rewilding has not been confined to North America and Europe. Rewilding initiatives are emerging in every continent and even in island nations. On Mauritius, for example, non-native tortoises have been successfully introduced as ‘taxon‡ substitutes’ for an endemic giant tortoise, the extinction of which had caused ecosystem dysfunction and loss of native wildlife. Moreover, some consider the restoration of southern Africa’s wildlife, which was almost wiped out during the anti-apartheid struggle for independence, a constrained form of rewilding. The policy to allow landowners to claim wildlife on their land as property initiated a large-scale transformation of struggling farms to private game reserves and the creation of a thriving wildlife economy, based on a blend of safari tourism, game hunting and wild meat production.

The possibility of moving beyond protecting past natural baselines to restore new and healthy wild places is driving innovation and a fresh philosophy of nature conservation. For many, rewilding offers a new and complementary conservation agenda that is empowering, hopeful and ambitious. Twentieth-century conservation science and practice did much to protect important natural areas and avoid extinctions. Rewilding builds on these successes by reintroducing functional species in natural areas, restoring degraded lands into thriving new natural assets.

Many leading rewilders are motivated by visions of working with recovering forces of nature to develop nature-based solutions to contemporary social, economic and environmental challenges, such as rural depopulation, soil degradation, public health and climate change. A body of practice and scientific evidence is building to suggest that rewilding could generate value in terms of natural flood management, carbon sequestration, control of invasive species, nature-based economies, and public health. Several leading European rewilders believe that rewilding is also about reconnecting wilder nature with modern society; they see nature as an ally in solving modern socio-economic issues. Later in this book we will take a tour of some rewilding initiatives that exemplify this potential and that are simultaneously shaping an applied science of ecological recovery.

This change in narrative, from nature protection as an obligation, to nature recovery using rewilding approaches as a solution, is attracting interest from policy-makers, thought leaders and investors. As we shall see, leading ecology research groups, aided by major developments in technology, are rising to this challenge and policy-makers are beginning to create spaces where a new integrative ecology can be trialled and developed.

Rewilding science is exciting – and it is happening. Although a scientific definition has yet to be agreed, there is an emerging consensus that rewilding aims to restore food webs, natural disturbances and dispersal, and that the interactions between these ecological processes foster complex and self-organising ecosystems. What makes this science radical is its interplay with the new approaches to ecological restoration being pioneered by progressive conservationists. This is imbuing the conservation movement with new purpose, ambition and confidence and the prospect of positive 21st-century environmentalism that acts to recover our planet’s biosphere for the benefit of all life – human and non-human.

*

The science of rewilding is underpinned by a new appreciation of the role of megafauna in creating the conditions for biological diversity and abundance to emerge. This account of rewilding science will start with two chapters that explore how grasslands and mega-herbivores co-evolved and interacted with woody vegetation to produce a rich array of micro-habitats and how, over the millennia, our human ancestors caused the demise of the megafauna and then ordered and simplified landscapes such that nature became impoverished. Drawing on this insight, we then review four pioneering rewilding projects (including those just mentioned) that all broke from the traditional focus on endangered species and habitats to experiment with restoring the dynamic interactions between large animals and the ecosystem. The following two chapters will introduce the latest ecological thinking on how interactions between megafauna, vegetation and natural disturbance cause ecosystems to expand and diversify, and the new connections that are being made between the demise of megafauna and the functioning of ecological systems at the continental and even planetary scale. In the last part of the book we explore some of the ethical, political and practical aspects of rewilding and look at the complexities of real-world action. We end with ten predictions for the future direction of rewilding which we hope will inspire discussion and debate.

* A group of a particular herbivore species that exploit the same resources, or that exploit different resources in related ways.

† The term ‘trophic’ refers to the transfer of energy between vegetation and animals via food webs, for example prey and predators.

‡ A group of organisms that are assumed to be related.

2

MEGAFAUNA PASTS

If we stop and take a moment to think about the natural regions of our planet, a picture of oceans, ice-caps, deserts, tropical rainforests and temperate woodlands is likely to come to mind. Some of us may also picture the African savannas, Asian steppes and American prairies, but a common view is that on land, trees are the natural vegetation except in the more extreme climatic conditions of high mountains and the polar regions. This view is undergoing revision as paleo-ecology reveals that for millions of years abundant megafauna (animals weighing more than 40kg) were a feature of our land and oceans.

On land, mega-herbivores co-evolved alongside grasses and thorny scrub to cover vast areas of the planet. These grassland ecosystems were characterised by a diversity of micro-habitats that produced abundant and diverse natures. Then, between 10,000 and 30,000 years ago, in human pre-history, something dramatic happened to our planet’s ecology. Megafauna disappeared from much of the Earth and many species went extinct. As megafauna disappeared many terrestrial ecosystems transitioned from grassland to scrub and then towards different, often more woody habitats towards the end of the Holocene (c. 10,000 years ago). Some, such as the American great plains and Indochinese savannas, survived into the last century – and the African savannas are thankfully still with us, although under constant threat.

Elsewhere, cattle- and goat-herding, shepherding and ranching maintained simplified yet biodiverse grassland and wood-pasture ecosystems, but these have gone into sharp decline as a result of intensive livestock farming, land abandonment and rural depopulation in the lowlands. Overall, our planet’s terrestrial ecosystems have moved towards the extremes of the wood-pasture gradient: less productive and abandoned lands have become woodier, and lands with more productive soils have become intensively managed grasslands or agricultural fields. As a result, natural grasslands and all their gradations towards scrublands and forests are at risk. Rewilding is in part about recovering these grasslands, scrub and forests and the ecological richness they produce.

A similar phenomenon has occurred in the marine environment during the last five centuries, as ships took to the oceans searching for new lands and marine resources – whales, seals, turtles and fish – to exploit. Although the impact of massive declines of megafauna within marine ecosystems is less well understood and the detail lacking, it is known that some species, such as whales, have a significant impact on ecological functionality and Earth systems. We will explore these phenomena further, for both mega-herbivores and marine fauna, in Chapter 6. But first we need to reveal the evidence supporting the view that mega-herbivores and grasslands co-evolved and that different combinations (mosaics) of grasslands, scrubland and woodlands once covered vast swathes of our planet for millennia. This is quite technical to illustrate but worth the effort, because it offers an enticing view of what is possible in terms of rewilding and provides a potential baseline for socio-ecological ‘well-being’ and biodiversity to be measured.

The evidence for grasslands

When thinking about how to save or restore the planet, most of us probably imagine trees rather than grasses. Grasses seem somehow domesticated: we know them as sports pitches, lawns, pastures and vast fields of wheat. It is easy to overlook the fact that humble grasses are the basis of one of our planet’s most productive ecosystems – and one that we could restore and rewild. However, as the disciplines of plant ecology, paleontology and evolution come together, this is just what many scientists are starting to think.

Advances in technology are bringing about a step-change in our ability to analyse and understand past ecosystems and the evolution of plants and animals over time. Until recently, the general view was that the natural vegetation of a region was the outcome of interactions between climate, topography and latitude (in effect, temperature and sunlight). This is now being revised as evidence builds for the role of grazing and disturbance by large herbivores in shaping the natural vegetation of an area. This new insight is a key pillar of the science of rewilding and the resulting efforts to reassemble the once widespread mixes of large herbivore species, something we will discuss in more detail in Chapter 8.

In many areas of ecological research, scientists use proxies or markers to build a picture of ecosystems. Long-term ecologists, those who try to reconstruct past systems, have traditionally used pollen and carbon-14 dating as indicators of the composition of past vegetation. Pollen grains persist over thousands of years in sediment cores, taken from areas such as lakes, where sediment has built up over millennia. Carbon-14 enables different segments of the core to be dated precisely, thereby allowing the construction of vegetation histories. However, as we are now beginning to realise, grass pollen is more fragile than that of trees and other woody plants and as a result it does not persist in the cores to the same extent. Put another way, the pollen record offers evidence of past woody vegetation but not the overall vegetation composition of a biome* or region.

Technological advances in microscopy have now provided scientists with another indicator: the tiny silica particles, called phytoliths, which form the cellulose that creates the supportive structures of grass leaves. Phytoliths are micro-fossils that can only be distinguished at magnifications greater than one thousand. They tend to survive longer than pollen and bones and will not have been blown around like pollen. Furthermore, they differ in shape, and it’s possible to identify different genera of plants from phytoliths. This new addition to the research toolkit is helping scientists create a clearer picture of the relative abundance of grassy and woody vegetation in past ecosystems, and to understand vegetation changes over time.

Other forms of evidence of the shift in balance from woody to grassland vegetation are emerging from the study of fossil soils and the teeth of animal remains. As we will see shortly, grasses evolved mat-like root structures which interact with worms and soil organisms to create dark organic soils. These form distinct soil layers called mollic epipedons that enable researchers, in combination with other factors, to identify and date past ecosystems. Studying the wear on fossil teeth is a means to understand the broad types of vegetation that were eaten by ancient herbivores, at least towards the end of their life.

The power of these techniques is enhanced by the development of large databases on fossil mammals, plants and increasingly invertebrates. These databases make it easier for scientists to identify species in their samples, identify associations between species, build evolutionary trees and locate sudden or rapid changes in vegetation and animals. The latest addition to the scientific toolbox is ancient DNA – the ability of powerful computer programs to match and assemble tiny fragments of DNA into strings that can be compared against reference collections of gene sequences of known species and even particular environmental locations such as river systems. New techniques have created a picture of the past which is good enough to know that grassland herbivore systems were once much more widespread, and that therefore this is the ‘natural’ situation for our planet. As these techniques continue to improve, the resolution of our picture of the ecosystems of 15,000 years ago will also improve and the story will become more intriguing.

The origins of grasslands

In order to understand the science of rewilding we do not need to go into great detail about the evolution of grasslands. However, we do need to understand the interacting factors that contributed to the evolution of grasslands and megafauna (as outlined in Figure 1). This is because the grassland-megafauna dynamic gave rise to diverse ecosystems, rich in plants and animals. The subsequent demise, domestication and simplification of these interactions is what rewilding seeks to reverse.

Fig. 1: Factors affecting the relative dominance of grasses and woody vegetation.

Following the disappearance of the dinosaurs 65 million years ago, woody plants had a chance to thrive. Paleontologists describe the world after the dinosaurs as a ‘hot house’: an epoch when the climate was warm, moist and stable and there were no huge dinosaurs to eat and trample trees and shrubs. In the millions of years after the dinosaurs, woody vegetation dominated our planet. However, over time different forms of grassland gained a foothold in areas subject to major climatic and periodic disturbance events, such as extremes of temperature, wildfires, landslides, rivers shifting their course, ash falls from volcanic eruptions, floods, droughts, cyclones and sandstorms. Grasses lack lignin, the compound that enables the formation of rigid cell walls and that produces wood and bark. Instead, grass species deploy cellulose to give structure. Cellulose is a weaker compound than lignin, but it is quicker to incorporate in cell walls. As a result, grasses can grow faster than trees, and they developed spreading rather than branching growth forms and shallow rather than deep root systems. This is how they can grow on land prone to extreme weather and frequent disturbance.

The rise of the grasses

Around 40 million years ago, our planet entered a period of massive geological activity. Continents started to reconfigure and collide, pushing up mountain ranges, plateaus and volcanoes. These processes created unstable mountains, vast windswept plains, and huge new river systems. These new topographies changed seasonality patterns and caused the climate to cool. This tumultuous period in our planet’s history created the conditions for grasses to evolve and flourish. Grasses quickly colonised areas newly rid of woody plants by some form of upheaval. However, their long, dry stems were easily ignited by lightning, so they invested in producing seeds quickly and relying on those seeds to survive the heat and grow again. In areas without lightning storms, the mats of dead grass stems provided shelter and nutrients for woody plants to regain a foothold and recolonise disturbed areas. Many such areas were too unstable or windy for fast-growing annual grasses to produce sufficient seeds to recover in numbers. In these areas, grasses evolved matted root systems and were resilient to being trampled or buried: food reserves in their roots enabled them to send up new shoots where the disturbance event was not too severe. These perennial grasses, as they are nowadays known, could also withstand their leaves being burnt or eaten and so spread into more stable landforms.

Disturbance apart, a key factor in the rise of grasslands was the evolution of a new photosynthetic pathway in so-called C4 grasses. Photosynthesis is the process by which water and carbon dioxide are converted, using the Sun’s energy, into simple sugars. Up until around 25 million years ago, the photosynthetic pathways in all plants were able to create first-stage molecules with three carbon atoms. Certain grasses evolved an additional and more efficient pathway that fixed carbon in four-atom molecules. This pathway evolved independently at least nine times and may have been a response to low levels of atmospheric carbon. The evolution of these C4 grasses accelerated between about 8 million and 5 million years ago in warmer and moister regions, and their ability to put on bulk quickly and out-compete woody seedlings caused the expansion of grasslands globally. Leaf-browsing mammalian herbivores responded to this change and evolved to graze both C4 and C3 grasses, heralding one of the most important periods of ecological change and diversification in our planet’s history.

The evolution of grazers

Species of small mammal made it through the apocalyptic conditions that followed the asteroid strike that wiped out the dinosaurs. In the millions of years following this cataclysmic event, the diversity of mammal species expanded alongside the recovery and spread of woody vegetation. Many tree species evolved large, nutritious seeds and fruits that were attractive for mammals to eat and therefore allowed the distribution of seeds in their dung. We will come back to this relationship in Chapter 6 when we explore the new science of the impact of megafauna extinctions on Earth systems. Just as plants were evolving strategies to enrol mammals in their movement, mammals were evolving the ability to eat the softer leaves and twigs of woody vegetation. However, three evolutionary ‘innovations’ emerged that enabled certain groups of mammals to take advantage of the expansion of grasslands starting 40 million years ago: trunks; the ability to ruminate (ferment grasses internally); and the formation of dentition able to deal with abrasive silica particles – the aforementioned phytoliths in grass leaves.

Proboscideans – mammals with trunks

The elephant’s trunk is a truly remarkable appendage – it has power, dexterity and sensitivity and is perfect for grasping vegetation, knocking off unwanted roughness and dirt, and folding it into a ball to place in the mouth. Ancestors of modern-day elephants lived during the Paleocene and Eocene epochs, 58–38 million years ago, but were less than a metre tall with no more than an elongated upper lip. The trunk or proboscis from which this extraordinary order of mammals takes its scientific name, Proboscidea, evolved slowly over time but accelerated as elephants radiated outwards from their African origins, in response to the spread of grasslands.

Elephants were originally browsers, using their modest trunks to pull down and break off leafy branches, but as grasses spread, they shifted to a grazing strategy. Their dexterous trunk could easily grasp clumps of grass, and in open grassland habitats, elephants could feed at a faster rate than in taller and tougher forest. This was an important adaptation because elephants have poor digestion and half of the vegetation that goes in comes out undigested. The fossil record shows a sudden increase in the variety of proboscises and the emergence of grazing species with different dentition to their forest ancestors. The diversity of Proboscideans was at its height around 8–10 million years ago, when more than 120 species in six distinct families roamed the Earth. The number of species went into sharp decline between 3 and 7 million years ago; one theory suggests that this was due to the rise of intelligence and other behavioural adaptations in the Elephantidae family, which enabled them to live in a wider range of environments and out-compete other, less flexible Proboscidean species.

Grasslands and elephants were made for each other. Elephants knock down, debark and consume woody vegetation, thereby creating and maintaining open grasslands. Officials in some African countries worry about the impact of elephant herds on woody savanna ecosystems and carry out culls to maintain a balance between grasses and woodland.

Ruminants

While the early Proboscideans were evolving a high-consumption strategy to deal with the difficulty of digesting plant material, another group of mammals evolved a quite different approach. This was to enrol micro-organisms to help break down the cellulose wall of plant cells and convert the nutrients inside into fatty acids that could be absorbed by the gut. We humans can, of course, extract nutrients from plant material. As it passes through our mouth and stomach, we break plant material into small fragments that can be worked on by microbes in our large intestine. We are better at digesting plant material than elephants but not nearly so good as the ruminants. Many cultures have learnt to ferment vegetables to make them nutritious – German sauerkraut and Korean kimchi being well-known examples. However, ruminant mammals developed organs and a digestive system that internalises fermentation. Cattle have a big, round, heavy body shape because they are walking fermentation vats.

Like elephants, the first ruminants evolved around 50 million years ago in forests. They were small and omnivorous and probably not unlike the primitive chevrotain, a type of small deer known as the mouse-deer, which still inhabits the rainforests of Malaysia. They evolved a fore-stomach with chambers, called a reticulorumen, holding populations of bacteria, fungi, protozoa and other micro-organisms with the ability to break down cellulose under anaerobic conditions. The fore-stomach enables a two-way digestive system. Rather than food going one way, as is the case in most mammals, ruminants can regurgitate it, ‘chew the cud’ to further fragment the plant material and return it to the fermentation vat.

As we have seen, the first ruminants were forest-dwellers, and they fed on dicotyledons: plants with two veins and with branching leaf and root structures (as opposed to monocotyledons such as grasses). This ancient and widespread group of plants had evolved chemical defences to repel the unwanted attentions of insects. To deal with this reality, ruminants evolved a large liver to break down the chemicals and a mobile feeding strategy for seeking out younger and more delicate leaves. This mobile life placed constraints on the size of the rumen. Deer, elk, chamois, giraffe and kudu are all modern-day examples of this model of ‘fermentation on the hoof’.

As grasslands expanded, ruminants turned to eating them and benefited from the lack of insect-repelling defences and the tough lignin contained in many woody species. As noted above, grasses deploy cellulose to provide structure and cellulose cell walls are difficult to break down. However, this expansive, easy-to-access and more palatable food source led to the evolution of a new wave of mammals, including cattle and sheep, with larger and more complex fermentation vats. With smaller livers and a larger, more efficient rumen, these animals were able to process older and taller grass with high cellulose content – what the agriculturalists refer to as ‘rough grazing’. This particular form of ruminating is the reason why cattle and sheep have been fully domesticated, rather than deer. They are more suited to living in enclosed spaces and eating hay.

Hypsodonts – mammals with hard-wearing teeth

The elephants and ruminants had existing adaptations – a proto-trunk and fore-stomach – that enabled them to switch to a grass diet and expand and evolve with the spread of grasslands. A third physical adaption emerged as a rapid response to the expansion of grassland. It is known as hypsodonty and is what characterises horses and rhinos, although it has also evolved in ruminant cattle, deer, and even the giant ground sloth of South America. The study of phytoliths has enabled scientists to conclusively establish that hypsodonty evolved after and not before the grasslands increased, becoming common in the fossil record approximately 4 million years later.

Hypsodonty describes a pattern of dentition identified by archaeologists studying fossil jaws. It refers to high-crowned teeth with thick enamel, extending well above the gums. As already indicated, it evolved a number of times, but the most complete scientific evidence concerns the evolution of horses in the great plains of North America. It is understood to be an adaptation to cope with abrasive, silica-rich grasses and the windblown grit and dust which covered grasses in exposed plateau, steppe and plain environments.

Grazers with high-crowned teeth have a performance advantage over the course of their life. It solves the problem of tooth wear from silica phytoliths and grit for a good number of years and enables more efficient and powerful mastication. This fragments plant material, preparing it for more effective microbial digestion in the hind gut.

Predators followed the herbivores out of the forests and into the grasslands and in these more open and exposed habitats the herbivores evolved predator defences in the form of speed, size, horns, antlers, camouflage and herding behaviours.

The grassland-megafauna biome

Starting in earnest around 20 million years ago, the rise of grasslands and mega-herbivores introduced a new pressure alongside climate and topography which shaped the vegetation of a region. The rise of mammals with the ability to eat grass and to browse, smash and trample young trees increased the area where grasslands became the dominant vegetation. Grazing pressure maintained, diversified and extended grasslands. Grazing interacted with a third major determinant of vegetation structure – fire – especially in regions where soil was poor and grazing light, leading to the build-up of dry, combustible biomass.

Up until the migration of modern humans out of Africa 70,000–50,000 years ago, grassland-megafauna biomes covered immense swathes of the planet, out-competing forests in regions where temperatures and precipitation were lower or strongly seasonal. In 2005, South African ecologist William Bond challenged the prevalent ‘green world’ hypothesis by arguing that large parts of it were brown or black. In his ‘multi-coloured’ view, Bond argued that vegetation communities in any given locality may have had elements of three possible ecosystems depending on the history, magnitude and nature of different types of control – available resources (the green part), grazers (the brown part) and fire (the black part). These interactions created a diverse and dynamic global ecology with numerous niches for organisms to evolve and thrive. Our planet was vibrant and bursting with life.

Evidence supporting a multi-coloured view of the world and the co-evolution of grassland-megafauna systems has been around for decades, but it has remained in specialist domains of plant ecology and mammal evolution and taxonomy. It is only in recent years that technology has expanded the volume of data and made it easier for scientists to read across disciplines. This has resolved many competing views and created a clearer image of the past. In doing so it is challenging the prevailing view among conservation scientists, policy-makers and citizens that forests are the ‘natural vegetation’ of our planet. It is also challenging the view that global efforts should predominantly protect and restore nature by focusing on tree biomes, particularly in the tropics where warm, wet and stable conditions have allowed a myriad of lifeforms to evolve.

Rewilding science and practice is about embracing the implications of this clearer view of our planet’s ecological history. In the next chapter, we will explore the impacts of humanity on the grassland-megafauna systems. Then we will look in detail at the interactions between herbivores and vegetation and the mechanisms that created biological diversity and abundance.

* A large, naturally occurring community of species occupying a major habitat, e.g. savanna or forest.

3

DOWNGRADING OUR PLANET

The co-evolution of grasslands and herbivores produced some of the most impressive mammals ever to have walked the Earth: woolly mammoths and mastodons, giant ground sloths, huge burrowing armadillos and the fabled sabre-toothed cats, along with horses, camels and bison. The last chapter painted a picture of grass-eating herbivores holding back succession by woody plants. In reality, the rise of grazers produced diverse vegetation mosaics: inedible herbs, thorny bushes and fast-growing trees all evolved to resist or get ahead of the effect of grazers. Predators such as sabre-toothed cats and cave lions evolved to prey on these herbivores, which affected both the pattern and intensity of grazing pressure. Similarly, interactions between soil nutrients and climate further affected the balance and distribution of grassy and woody vegetation.

A bird’s-eye view of a temperate Pleistocene world would have revealed a patchy mosaic of grassland, scrub, groves and forests. Herds of mammoths, camels, llamas and horses would have been visible but so would large, less social animals, such as giant ground sloths and gomphotheres (an elephant relative) sedately browsing on trees along the woodland edges. Zooming in, the aerial observer would see a myriad of smaller species. The Pleistocene megafauna supported their own ecosystem of ticks, parasites, scavengers and decomposers and their constant grazing, scuffing, trampling and defecating created a variety of niches for other animals and plants to occupy and evolve.

The disappearing

Then something happened. Around 130,000 years ago the megafauna started going extinct – 177 of the 294 known mammalian megafauna species disappeared between then and 1,000 years before the present, based on current knowledge of the fossil record. Extinctions are normal in the fossil record but usually the vanished species is replaced by a different one adapted to occupy a similar niche. The notion of ‘replacement species’ where a fitter species evolves to take the place of an existing one is a key concept in Darwinian evolutionary theory. The megafauna extinctions are different. They happened relatively recently, and new or equivalent species did not exist to usurp them or fill their vacant niche. Nothing remotely like the Volkswagen Beetle-sized armadillo has appeared since this remarkable mammal disappeared from the landscapes of South America.

Table 1: Mammal megafauna extinctions (species over 40kg) during the Pleistocene–Holocene transition.

Region | No. of Pleistocene megafauna species | No. of extinctions | Percentage loss
Sub-Saharan Africa | 50 | 8 | 16
Asia | 46 | 24 | 52
Europe | 39 | 23 | 59
Australasia | 27 | 19 | 71
North America | 61 | 45 | 74
South America | 71 | 58 | 82

These megafauna extinctions occurred during a period of great climatic instability. The Pleistocene epoch is popularly known as the ice ages – a period of planetary cooling when vast ice sheets covered the northern hemisphere, as far south as Chicago in the US, and the British Midlands and northern Germany in Europe. Great ice sheets advanced and retreated, reaching their last maximum extent just 22,000 years ago. Until recently, most paleontologists assumed that the ice age cold caused the extinction of many species of megafauna. They reasoned that the colder climate would have reduced grass productivity, making it harder for these large-bodied beasts to find forage and maintain their body temperatures.

However, in 1940 Willard Libby invented a new method to investigate the past: radiocarbon dating. Libby’s genius was to recognise a connection between a radioactive isotope of carbon (known as carbon-14 or ¹⁴C) produced by cosmic radiation in the atmosphere, and the carbon in animal bones. All living matter contains carbon and is part of the planetary carbon cycle. The ratio of ¹⁴C to ¹²C (another isotope of carbon) in the atmosphere is very small but nonetheless measurable. Living tissues take up ¹⁴C in similar proportions to its presence in the atmosphere. When an organism dies, the radioactive carbon starts to decay at a rate where half the ¹⁴C atoms are lost over a period of 5,730 years. Libby developed a technique to measure the ratio of ¹⁴C to ¹²C in organic material such as bones, trees and soil sediments. The difference between this ratio and the ratio of ¹⁴C to ¹²C in the atmosphere, gives a time since death. Scientists can date material back to 40,000 years ago, or seven half-lives of carbon-14, but after this the proportion of ¹⁴C becomes too small to rule out spurious results caused by contamination. Radiocarbon dating revolutionised the precision with which organic materials could be dated and it is now possible to measure time of death down to a few centuries, with further accuracy coming from scientists calibrating results against material of known age, such as wood from the pyramids, tree rings or sediments laid down annually.

As zoologists began to radiocarbon date the remains of Pleistocene mammals, a new picture emerged. Although megafauna extinctions started earlier, a sudden acceleration began 22,000 years ago. This timing aligned with the dispersal of Homo sapiens around the planet and gave rise to the theory of ‘overkill’ to explain the extinctions.

Overkill

Paul Martin, a University of Arizona zoologist and geoscientist, was among the first to make the connection between megafauna extinctions and human hunting – the ‘overkill’ theory. Martin has been described as a ‘time traveller’ – someone with the imagination and command of facts to think across eras and continents. In 1967, and again in 1984, he convened conferences to review and discuss advances in evidence and knowledge, and to each he invited opponents of the overkill hypothesis, who maintained that while human impact may have played a part, climatic change (or ‘overchill’) was the primary driver of Pleistocene extinctions.

In a nutshell, the overkill hypothesis is as follows. Early hominids evolved in the grassland-megafauna ecosystems of Africa, and then moved into Europe where a second period of human evolution took place. Sergey Zimov, founder of the Pleistocene Park (see Chapter 4), has suggested that we humans started out as scavengers of carcasses, using our intellect and tools to break the large marrow-filled bones. Over time, we developed spears and hunting behaviours, and the megafauna of Africa, and to a lesser extent Europe, were able to adapt to the rise of a hominid predator. They did so by becoming more wary, aggressive, mobile or crepuscular (active at dawn and dusk). However, in Australia and the Americas, where accomplished human hunters encountered a ‘naive’ megafauna unadapted to human predation, the consequences for megafauna were catastrophic.

In the last five years, the study of ancient DNA has transformed our understanding of human evolution, dispersal and mixing. This new science is brilliantly explained in the book Who We Are and How We Got Here by David Reich. Scientists have yet to integrate this new knowledge with research on megafauna extinctions and domestication, but it reinforces the match between knowledge on successive waves of human dispersal around the planet and the pattern and intensity of megafauna extinctions.

Approximately 40,000 years ago humans crossed the deep ocean trenches in eastern Indonesia and settled the continent of Australia. This date coincides with the disappearance of the continent’s marsupial megafauna. These included a hippopotamus-sized diprotodon, a marsupial tapir, and the 3-metre-tall giant short-faced kangaroo. The extinctions of 21 genera in Australia have been dated to just before or soon after humans colonised the continent, and are not linked to any major climate events, either regionally or globally; and nine species are definitely known to have gone extinct after the arrival of humans.

Opponents of the Australasian overkill hypothesis point to a lack of sophisticated hunting tools and megafauna kill sites in the fossil record. However, population modelling indicates that such evidence is unnecessary to establish the validity of overkill. Models show that systematic low-level killing of smaller, younger individuals (one to two kills per ten people per year) would be enough to drive a population to extinction within a matter of centuries due to the slow life histories of large animals. Later megafaunal extinctions in New Zealand also do not coincide with climate changes. In fact, it appears that species of large flightless birds were able to adapt to various climatic changes over thousands of years, and their likelihood of extinction would have been much lower without human intervention. However, the science is far from settled.

The movement of human hunters across the Bering Strait through an ice-free corridor that opened up to link Siberia and Alaska about 15,000 years ago gives greater credence to the overkill theorists. In North and South America, they found savanna-like biomes, populated by four species of elephant, mastodons, gomphotheres, four species of giant sloth, and two species of giant armadillo, along with camels, horses, bison and several species of deer. These animals had learnt behaviours to cope with sabre-toothed cats, cave lions and dire wolves but did not recognise humans as a threat. They were, in effect, behaviourally defenceless to human hunting. As a result, populations collapsed over the period of a few centuries, as the number of animals hunted exceeded the rate at which slow-breeding megafauna could reproduce.

The fact that the mammoths survived until around 2,500 years ago on Wrangel Island north of Siberia and on St Paul Island south-west of the Alaskan mainland, which were bypassed by successive waves of human settlement, adds weight to the overkill hypothesis. However, it remained controversial until 2014, when Chris Sandom, from the University of Sussex, and colleagues removed this barrier by painstakingly entering all the evidence into a model to test the three competing hypotheses: hunting pressure, climate, and mixed climate and hunting. Their results confirmed that the overkill hypothesis was the best fit for all regions except Europe, where the mixed hypothesis best fitted the data.

In retrospect, it is interesting to ask why was there so much resistance to the overkill hypothesis. The evidence may have been patchy, but the logic was and is more robust than the arguments proffered by the ‘overchill’ camp. One reason is that established scientific frameworks are hard to shift. In 1936, one of the fathers of the science of ecology, Frederic Clements, had proposed the idea of ‘climax’ vegetation – the concept that in any given region, vegetation would succeed to a natural state of forest. The idea that animals could be a force on a par with temperature, precipitation and day-length unsettled this foundational idea, and the science developed from it. A second reason was cultural and political. During the 1980s, a major agenda of western environmentalism was to halt rampant deforestation at the hands of loggers and agricultural interests. Linked to this was growing concern for the plight of indigenous and forest-dwelling people. Organisations such as Survival International and films such as John Boorman’s The Emerald Forest portrayed indigenous tribes as living in harmony with nature. A scientific hypothesis that framed these people as the descendants of settlers who had caused the collapse of megafauna, leading to the spread of forests, sounded unhelpful and insensitive. It was out of kilter with the times – and perhaps still is.

Pleistocene rewilding

In the concluding chapter of Paul Martin’s 2005 book Twilight of the Mammoths: Ice Age Extinctions and the Rewilding of America, he argued that the American focus on conserving and restoring wilderness was ‘historically too short-sighted and far too tame’, and that the ‘ultimate in American rewilding’ would be restoring relatives or analogues of the missing keystone species.

As mentioned in Chapter 1, the term rewilding was coined by Dave Foreman in 1992. Foreman and the other US scientists had a restoration vision that was oriented around single species and particularly predators such as wolves, cougars and grizzly bears. These species had been wiped out from large parts of their native American range and, as in the case of the wolf, were even missing from iconic wilderness parks, including Yellowstone. However, Paul Martin pointed out that this rewilding agenda was only about restoring what North America still had – the impoverished suite of species left over from the late Pleistocene overkill. In so doing, he was one of a number of scientists who raised questions about what are termed ‘natural baselines’ – the points in history which the experts, who develop nature conservation law and policy, determine as the natural state to protect, restore and maintain. Across large parts of the world these are set at the time of European colonisation, when naturalists began to describe the new fauna and flora they encountered. In North America, conservationists turn to the landing of Christopher Columbus in 1492 as the de facto natural baseline that they then seek to restore and protect. Across most of Europe the baseline chosen was the mid-19th century, before the impacts of industrialisation and a time when the European landscapes seemed more harmonious, tranquil and therefore natural. Martin’s book introduced an unsettling question for modern institutions of conservation. This was clearly articulated in a 2015 article by the Brazilian ecologist Mauro Galetti, who asked: ‘Why are we protecting the ecological impacts of Holocene extinctions?’

Twilight of the Mammoths prompted a gathering of twelve progressive US conservation scientists and leading conservation biologists at a ranch in the Chihuahuan Desert of New Mexico. They produced a radical and optimistic agenda for North American conservation called ‘Pleistocene Rewilding’, as we saw in Chapter 1. Josh Donlan, a young conservation biologist from Cornell University in New York, followed this up by writing two articles – a summary published in the leading journal Science and a longer exposition in The American Naturalist in 2006, which took the form of a manifesto: a call to conservation scientists to reject the ‘doom and gloom’ conservation narrative and to expand their ambition from saving wild places to rewilding and reinvigorating them.

This agenda was, and still is, bold and radical: criticisms were swift and varied. We will highlight some of these later. However, Donlan and those who inspired him clearly articulated a key rewilding principle, namely that ‘conservation should use ecological history as a guide to actively restore ecological and evolutionary processes’. This principle can also be summed up as ‘taking inspiration from multiple past natures to shape future natures’. This proposes a clear departure from the established focus of conservation, which was avoiding extinctions and managing habitats to maintain an assumed natural baseline.

The Pleistocene rewilding agenda also emphasised the concept of taxon substitution: the idea that living species from different biogeographic regions could be introduced to replicate the roles of extinct species. These practices are increasingly widespread and will be discussed in the next chapter. However, Donlan and his colleagues’ suggestion to introduce African cheetahs into North America as a taxon substitute for the two extinct species of Pleistocene American cheetah was too controversial for many. The rewilders argued that these cheetahs influenced the speed and visual acuity of pronghorn antelopes and that returning such proxy species to the wild would reinstate these evolutionary interactions. They reinforced their argument by asserting that cheetah populations in Africa are under threat, so new populations in the south-western US could help ensure their survival and, at the same time, provide ecotourism opportunities for ranchers.

The Pleistocene manifesto was fresh, radical and visionary; and while its focus was on North America, it provided a framework to consider the ecological impacts of early hominid expansion into different regions of the world.

The rise of agriculture and imperialism: the second downgrading of ecosystems

A second major downgrading of the Earth’s natural diversity and abundance began in the 16th century with the spread of agriculture and European colonisation of the Americas, Asia and Africa. The rise of more organised agriculture began to degrade two other ecological dynamics that are key to thriving ecosystems and that rewilding specifically seeks to restore. These are 1) natural disturbances, which as we will see in Chapter 6 are vital for creating the conditions for many animals to flourish; and 2) the ability of organisms to disperse and migrate across landscapes and continents. This is often referred to in the scientific literature as ecological connectivity.

The growth of settled agriculture around 8,000 years ago in the Middle East, Europe and Asia initially maintained and amplified aspects of the natural grassland and woodland mosaics, creating open habitats that benefited many species. For example, tilling land mimicked the rooting behaviours of wild boar on a scale that suited the ephemeral plants whose small flowers and seeds are favoured by a variety of species. Wheat cultivation was a boon to seed-eating mammals and birds and the animals that preyed on them, while irrigation channels and paddy fields extended the area of pond and slow-moving stream habitats.

Around 5,000 years ago a herding culture (the Yamnaya) emerged on the Asian steppes following the invention of the wheel. These herders spread into Europe and eastwards to the Altai Mountains of Central Asia and mixed with the agriculturalists, integrating herding and the breeding of draught animals with the growing of crops. This ensured that plenty of grazing grasslands remained, and herding semi-domesticated breeds of cattle, horses, goats and sheep in woodlands and upland regions maintained, and perhaps even restored dynamic interactions between grazing and vegetation. Significantly, the evolution and spread of the Yamnaya herding culture may have averted the extinction of Eurasia’s cattle and horse species and ultimately allowed the opportunity for rewilders to partially rebuild Europe’s megafauna guilds and their interactions with vegetation.

The ecosystem impacts of agriculture and resource extraction started to increase during the Middle Ages as farming became more commercial and organised, and as societies developed the engineering skills to drain land. For example, from the 15th century when windmills were developed to pump water, Dutch engineers became skilled at draining marshes and shallow lakes to create farmland, and started exporting their methods elsewhere. In England the vast fenlands of Lincolnshire and Cambridgeshire, covering thousands of square kilometres and supporting abundant wildlife, were largely drained in the 17th century. The drained peaty soils were, and still are, fantastic for growing root crops to support a growing population. But the loss of these wetlands didn’t just reduce natural abundance locally; it removed key breeding, stop-over and wintering areas for migratory species, thereby reducing long-distance dispersal and the flows of life across regions and continents.

Farmers also started to invest more in preparing land and protecting their crops and livestock. This took the form of draining and fencing fields and actively eradicating species that might prey on poultry and livestock, or that might compete for grass and/or breed with domesticated livestock. The category of ‘vermin’ entered the psyche of many cultures, and jackals, wildcats, birds of prey and martens were trapped and hunted, often with bounties paid out by government for eradication programmes. In addition, growing human populations needed wood for building fences and dwellings and for fuel, and the landscape in agricultural regions gradually become more open, with less vegetation diversity. Predators big and small were removed, and large herbivores confined to fenced areas.

Impacts of the age of discovery

Coinciding with the rise of agriculture, in the 16th and 17th centuries seafaring nations in western Europe embarked on voyages of discovery to explore the unknown riches and wonders of our planet. These voyages created the impetus for imperialism and the claiming and settling of territories across the globe. During the 18th century the Spanish and Portuguese focused their efforts on South America, the British on North America and the Indian sub-continent, the Dutch on the East Indies (present-day south-east Asia): then in the second part of the 19th century everyone scrambled to colonise territory in Africa and Indochina. Imperial expansion was fuelled by the industrial revolution, which generated a demand for resources and new markets and the technological, military and administrative capacity to deliver both. The impacts of colonialism on wildlife and ecosystems were profound and extended the effects of the late Holocene overkill to the world’s river systems, coastal areas and oceans. As territories were settled and plantations established, the new port towns created trading hubs out of which radiated trapping, hunting and fishing networks, penetrating deep into the continental interiors and out into the oceans.

The megafauna that survived the Holocene overkill were targeted by 19th-century commercial hunters, as were smaller species such as beavers and seals that offered pelts for the fur trade. Armed with guns, steel harpoons, wire snares and strong nets, the hunters had a devastating impact on wildlife, although as yet we lack a comprehensive understanding of the scale of their effect on ecosystems. At the time, natural abundance was normal and remarked upon only passing. It wasn’t until the 1870s that developments in cartography prompted imperial strategists to start mapping and measuring forest resources and planning their exploitation and management. Public awareness on the wanton slaughter of wildlife and the rising number of extinctions only started to build with the rise of the global news media towards the end of the 19th century, and the first international conference on wildlife protection was not until 1933.

What we know about the impact of commercial hunting on wildlife and ecosystems is patched together from a mix of explorers’ accounts, histories of colonial commerce, and a few better-researched case studies. For example, the slaughter of the bison herds of the North American plains is well known. At the height of the carnage, hunters mowed down herds with rifle fire, taking only their tongues, which were tinned and transported to the cities of the East Coast. The carcasses were left to decompose, after which the skulls and bigger bones were collected and ground into fertiliser.

The impact of the era of commercial whaling, for blubber to provide oils used in manufacturing, is also well documented, although scientists have only recently pointed out that these accounts focus on the exploitation of whales in the northern and southern oceans and overlook the fact that populations in the mid-Atlantic were hunted out in the Middle Ages.

Less well known is the defaunation of the world’s great river systems such as the Amazon, Mekong and Hudson. In the 19th century there was an enormous trade in freshwater turtle eggs collected from the Amazon, literally hundreds of millions a year, which were made into a fatty butter for export. Such were the numbers of freshwater turtles in the early 19th century that people reported hearing from several kilometres away the sounds of the shells knocking together as the turtles pulled out on sandbanks to breed. The pirarucu (also called arapaima), which at 3 metres long is among the world’s largest freshwater fish, was harpooned in such numbers that it disappeared from vast reaches of the Amazon, and the giant otter was hunted to near-extinction for its pelt. Fortunately, all these species survived, and their numbers are slowly recovering in some areas, but the Amazon is not the pristine wilderness we might think it to be.

It was not just commercial hunting that resulted in a second overkill of megafauna. New settlers needed to live off the land for a minimum of seven to ten years until their plantations started bearing produce or their imported livestock had grown in sufficient numbers to be ranched. This was especially the case in Africa, where game hunting was central to survival and became part of colonial life. However, as the ranching of domestic livestock increased, outbreaks of diseases such as rinderpest decimated native wildlife and livestock alike and led to a partitioning of the two. Fortunately, the rinderpest outbreak happened in the early 20th century when the reality of human-caused extinctions and the new morality of wildlife conservation was already taking root in western society. Colonial administrations acted to create wildlife refuges, game reserves and national parks, but also began the process of separating domestic and wild mega-herbivores and disrupting natural migrations with fencing.

Industrialisation and globalisation: the third downgrading of ecosystems

Industrialisation and the growth of trade in commodities across the vast reaches of colonial empires drove the expansion of transport arteries: navigable rivers, railways and roads that opened up remote areas to settlers and commercial interests and disrupted the natural dispersal of animals across landscapes and along rivers. Industrialisation marked the invention of new technologies to engineer, manage and exploit nature – the steam engine, water pump, rifle and tractor, for instance – and new processes to store, transport and manufacture natural products, for example canning factories, pulp mills and shipping lines. Industrialisation accelerated the settling and clearance of land for agriculture, logging of old-growth forests, the exploitation of wildlife and pollution of wetlands and rivers.

By the mid-20th century, river systems in many industrial countries were dead-zones, the growing use of agricultural pesticides (notably DDT) was having noticeable impacts on birds, and iconic African wildlife species such as the rhino were on the verge of extinction. A new environmental consciousness began to emerge among citizens of America and western Europe, and on 22 April 1970 millions of young people took to the streets for the first Earth Day. Governments around the world reacted. They negotiated international treaties, passed national legislation and set up departments to curb pollution, protect endangered species and protect a representative range of the world’s ecosystems big and small. These protective actions, together with the efforts of conservation groups, have managed to ‘hold the line’ and avoid the extinctions of known species and habitat types on a large scale. In some regions they have resulted in the comeback of predators, for example wolves in Europe. Unfortunately, they have not been able to halt widespread declines in the abundance of smaller species that were still common in the 1970s.

The sixth extinction

Today’s conservation science literature is full of talk of a ‘sixth extinction crisis’ and an ‘ecological emergency’. The rise of environmentalism in the 1970s also saw the beginning of systematic efforts to assess and monitor the state of the world’s nature. This was aided by the theory of island biogeography first articulated in 1967 by Robert MacArthur and Edward O. Wilson. They demonstrated a direct relationship between the size of an island and the number of different species present, and proposed that if the size of an area was reduced over time the number of species would ‘relax’ to a new and lower equilibrium. Scientists generated estimates of the number of species in major habitats, such as lowland tropical forest, by extrapolating data from field surveys; they then linked this to the rate of habitat loss (shrinking of the habitat ‘islands’) to produce figures for the number of species at risk of extinction. These estimates, together with data from schemes that directly monitor wildlife populations, are combined into an index to report on the state of nature.

The best known and most robust of these indices is the Living Planet Index generated by the World Wide Fund for Nature (WWF), the Zoological Society of London and the Biodiversity Indicators Partnership of the Convention on Biological Diversity. The Index shows a 60 per cent decline since 1970. The magnitude of the decline in biological abundance has recently been brought home by the alarming results of two studies. The first, published in 2017 by a team of German scientists led by Hans de Kroon, reported 75 per cent declines in flying insect biomass in German nature reserves since 1987. This gave credence to the so-called ‘windscreen phenomenon’ – a term given to anecdotal observations that drivers now experience far fewer insects splatted on their windscreens. The second, published in 2019 by a team from the Cornell Lab of Ornithology, reported a loss of 3 billion farmland birds since 1970. The Cornell team combined 50 years of organised citizen surveys of bird numbers with sophisticated computer models to come up with the figures.

Less talked about are the declines in freshwater biodiversity. Our lakes, rivers, marshes and deltas cover just 1 per cent of the Earth’s surface but are home to 10 per cent of all animal species and 30 per cent of all vertebrate species. However, these aquatic ecosystems receive far less attention than terrestrial ecosystems. Perhaps this is because life below the surface is harder to discern, and citizens in industrial countries have witnessed major improvements in water quality since the 1980s – rivers that stank with effluent are once again swimmable.

In summary, the science seems unequivocal: ecosystem downgrading is accelerating, despite the best efforts and some notable achievements of the nature protection policies and institutions established half a century ago.

Globalisation and the free-market economy

This depressing state of nature and ecosystems is the outcome of globalisation – the interlinking of economies, cultures and populations. Globalisation drives economic prosperity and consumption by enabling ‘low-friction’ cross-border trade in goods and services, technology, and flows of capital investment, people and information. Globalisation has allowed agricultural crops to be grown where conditions are best and exported globally, which attracts investment in technology to grow crops more efficiently and at scale. Field sizes have expanded to accommodate huge and increasingly automated machines that till, fertilise, apply pesticide and harvest at an industrial scale. These modern agricultural landscapes have been stabilised and sanitised; the soils are transformed from living systems to growing mediums. The messy, connected chaos needed by plants and animals has disappeared and it is hardly surprising that bird and insect numbers are in decline.

Globalisation supports the flow of capital into investments that generate a financial return that can be reinvested. Fifty years ago, it might have been difficult to raise the investment for a large infrastructure project from purely national markets. Not so anymore. It is nowadays much easier for capital to move across borders and therefore for governments and corporations to raise investment for infrastructure. Take hydropower dams, for example, which are a major threat to freshwater biodiversity. Free-flowing rivers support diverse, complex and dynamic ecosystems. In 2019 a team of Canadian and German scientists assessed 2 million kilometres of rivers globally and found that only 37 per cent of rivers longer than 1,000 kilometres remain free-flowing over their entire length, and only 23 per cent flow uninterrupted to the ocean. An earlier 2015 study estimated that river flow and connectivity is moderately or severely impacted by dams and water abstraction in 485 (48 per cent of) major river systems globally and that this will nearly double to 93 per cent by 2030 should all the proposed dams be built. The devastating impact of dams and other engineering on freshwater life is well known, and without action this is expected to continue. We will discuss river rewilding and efforts to reduce engineering infrastructure in river systems in Chapter 7.

The impact of globalisation on ecosystems is a long and depressing story, and scientists and activists are working to explain the scale and consequences to politicians, policy-makers, corporate leaders, investment managers and consumers. High-profile campaigns drawing attention to the rate and massive scale of tropical deforestation to grow palm oil in south-east Asia, and conversion of the dry forests of the vast Cerrado biome in Brazil to grow soya for global commodity markets, are generating concern – and a sense of unease with unbridled capitalism.

Rewilding in the 21st century

Rewilding science and practice is not anti-globalism, nor does it seek to restore what industrialisation has destroyed or damaged. As a visionary new agenda for conservation, it is realistic and pragmatic. Attempting to redress the damage wreaked on nature by palm oil and soya commodity markets is beyond the scope of rewilding at present. The flipside of globalisation is that it is also creating opportunities to upgrade ecosystems at scale. For example, the rise of highly mechanised agriculture is making farming unviable on many marginal lands. Large-scale land abandonment and rural depopulation in areas of eastern and southern Europe represents a chance to rebuild Europe’s lost mega-herbivore wood-pasture systems and generate new nature-based economic prospects for these regions.

Climate change, one of the most serious outcomes of industrialisation, is also creating an imperative to rethink river management. This is because highly engineered rivers are struggling to cope with the flows generated by the increasing frequency of extreme rainfall events. Natural approaches to river management, such as reconnecting rivers with their floodplains, are gaining interest and practical action.

In many ways, rewilding is an outcome of change and the need to rethink ways of doing conservation in our increasingly complex world. In the next chapter, we will explore the practical origins of rewilding and the roots of its pragmatic, innovative and solutions-orientated approach.

4

REWILDING’S PRACTICAL ORIGINS

In science, the distinction between fundamental (or basic) and applied research is important. The last two chapters described a body of fundamental research conducted by scientists wanting to fill gaps in knowledge, so they could answer the question of what caused the sudden demise of the megafauna at the end of the Pleistocene. These researchers worked in scientific academies such as universities and adopted the formal scientific method, based on deductive reasoning: this starts with a hypothesis or propositions based on the available evidence, and then collects and collates new evidence to test, debate and either refine or reject the hypothesis. As we learnt in the last chapter, this led more and more scientists to conclude that the ‘overkill’ hypothesis fits the evidence better than the competing hypothesis, that megafauna declined because the world became too cold (‘overchill’) or wet, or a combination of both. Their science was not motivated by a feeling that existing conservation needed a new agenda. The practical application of this science appeared when Paul Martin added the ‘So what?’ question and explored the implications of this new knowledge for nature conservation policy and practice.

Alongside this academic research, a number of applied scientists were making observations of the natural world that appeared out of synch with the scientific wisdom that structured the policy and practice of the nature conservation institutions they worked within. A few of these scientists had the combination of vision, boldness, powers of persuasion and opportunity to try out new approaches, inspired by their observations. Nowadays, these practical initiatives are often referred to as experiments in rewilding but they all began well before that term came into widespread use. The ‘big four’, in terms of their influence on the science, practice and public awareness of rewilding, are the Oostvaardersplassen (OVP, Netherlands), Yellowstone (USA), the Pleistocene Park (Russia) and the Mauritian islands in the Indian Ocean.

The stories of these four initiatives will be the focus of this chapter. The ecological and cultural context of each is very different, but the scientists involved have a number of things in common: they all developed a deep relationship with a particular place, were passionate and careful observers of nature, had the opportunity or good fortune to try out new approaches to conserving nature, and had a talent for inductive reasoning.

The inductive scientific method is often described as the deductive method turned upside down: it begins with observations and incidents and forms logical generalisations or theories based on these. In the context of rewilding, it usually starts with observations of nature over time that, in interaction with other knowledge and insights, generate new concepts and theories about how nature works. Some consider inductive methods less suited to the rigour and discipline of research institutes. However, as this chapter will show, when conservationists with a talent for inductive reasoning have the opportunity and freedom to try out their ideas in practice, exciting and unsettling new theories and approaches can emerge.

We will start with OVP, in part because it continues the grazing theme of earlier chapters and in part because, as we saw in Chapter 1, it initiated a European version of rewilding that challenged foundational assumptions in conservation science and practice.

The Oostvaardersplassen

The Netherlands is Europe’s most densely populated country, and the delta of the River Rhine on which it is founded is among the most engineered in the world. The Dutch are rightly famous for their ability to manage water and drain lands, and after the Second World War they invested heavily in drainage and agricultural infrastructure. By the 1980s the reclaimed delta landscapes (known as polders) were structured, fragmented, lacking in natural value and – tulip fields apart – aesthetically boring. This might seem an unexpected place for a radical and ambitious conservation approach to emerge, but a new generation of progressive Dutch ecologists felt there was little nature left to lose, and they believed it was time for conservationists to adopt a more ‘offensive’ rather than ‘defensive’ approach.

The OVP came into being by chance when a new polder intended for industrial development was abandoned due to the economic downturn caused by the 1973 oil crisis. Left to its own devices, the land began to succeed to reed marsh and willow scrub and attracted huge numbers of geese, which flocked to the area to moult their flight feathers. A young ecologist called Frans Vera, working for the Ministry of Agriculture, Nature Management and Fisheries, contemplated the effect of geese grazing on the spontaneous recovery of nature on the polder. In the 1980s most ecologists accepted the notion proposed by Frederic Clements in 1936 that vegetation succeeds along pathways towards a stable ‘climax community’ of high forest, and this strongly influenced ideas on how nature reserves should be managed in Europe and elsewhere: most were designated and managed to maintain examples of each successional stage. Vera observed that geese grazing ‘steered’ the development of vegetation on the OVP, creating mosaics of open water and marsh vegetation. Rather than herbivores merely following the succeeding stages of vegetation as conventional wisdom suggested, the geese were creating a vegetation that was optimal for them and other species.

Frans Vera is someone with a genius for looking at things differently and assembling disparate forms of evidence to develop, test and articulate new ideas. He is also fearless when it comes to challenging mainstream thinking, pointing out flaws in conventional ecological reasoning and formulating new explanations. His observations on the impacts of goose grazing inspired him to learn more about the history of interactions between herbivores, vegetation and people in Europe. He quickly realised that when botanists started to formalise ideas of ‘natural’ vegetation types in the late 19th century, they were missing a significant part of the jigsaw, because neither aurochs (wild cattle) nor horses were considered part of indigenous European fauna at that time.

The aurochs was described scientifically only in 1827 and it was assumed to have gone extinct at the end of the Pleistocene, some 15,000 years ago. However, a century later, it was established that the aurochs was the ancestor of domestic cattle and it is now known that wild aurochs survived in Europe into the 17th century. The inclusion of horses in the European fauna is even more recent. This is because ‘Clementsian’ logic – which claimed that high forest was the natural vegetation of Europe – excluded the possibility of native horses. As a result, horse remains from Neolithic sites were presumed to be those of domestic rather than wild animals. Vera considered this a clear example of the circular reasoning adopted by many conservation and ecological scientists. It is now known that a wild horse species, the tarpan, was once abundant across Europe and is the ancestor of domestic breeds. Many of these breeds are still genetically close to the original tarpan and live in semi-wild or feral conditions. Vera argued that if the logic is ‘straightened out’, there is ample evidence that African-like grassland mosaics created by the grazing impacts of herds of mega-herbivores once covered large swathes of Europe.

The OVP experiment

As the OVP landscape developed, there were suggestions that the area should be grazed with domestic cattle to halt the process of vegetation towards scrub and woodland. Vera and a colleague, Fred Baerselman, responded with a more radical and ambitious vision, namely that the OVP should become a unique experiment in nature development, based on the reassembly of the mix of free-living mega-herbivores that once roamed lowland Europe. Their superiors gave the go-ahead and in 1991 the OVP was designated as a nature reserve, with nature development as its guiding principle.

Red and roe deer were translocated from Scotland and other reserves in the Netherlands, and the team looked across Europe for primitive breeds of cattle and horse that could fulfil the ecological roles of aurochs and tarpan. They purchased Konik ponies from Poland which exhibit tarpan-like characteristics, and acquired a herd of Heck cattle. This is actually a recent breed, created in the 1920s in Germany by the Heck brothers, who crossed a number of primitive breeds to create a zoo exhibit of an animal, resembling the extinct aurochs. As the herds grew in size and adopted natural herd behaviours, the OVP took on the appearance of a ‘Serengeti behind the dykes’. Vera continued his observations of the dynamic interactions between grazing and vegetation, and the effects this had on plant and animal populations. As a result, the Ministry allowed him a sabbatical to formalise his ideas in a doctoral thesis.

Vera pointed to the New Forest in southern England as a surviving, if modified, example of a mega-herbivore-shaped landscape. Confusingly, the New Forest is actually very old. William the Conqueror declared it a royal hunting reserve in 1076 and for him and his court it was indeed their ‘New Forest’. It was chosen because it was rich in deer and other game, the consequence of an open wood-pasture landscape created by ancient practices of Commoners managing free-roaming herds of cattle, ponies and pigs. The New Forest witnessed a number of changes and threats in its 950-year history, but the mixed grazing practices continue into the present day and the area is one of the UK’s most biodiverse natural landscapes.

As well as providing an alternative reference point for European nature, Vera helpfully pointed out that the word ‘forest’ originally referred to partially wooded and unfenced areas used for hunting; its current meaning of large areas covered by trees, is more recent.

Theory of cyclic vegetation turnover

Vera’s thesis, published in 2000 as a book entitled Grazing Ecology and Forest History, caused quite a stir in European scientific circles. This was because he backed up his assertion that dynamic wood-pasture landscapes were a natural European archetype with a robust theory to explain how grazing produced these landscapes (Figure 2). His theory posits that vegetation is always at some place on a slow cycle of change. An explanation of the drivers of this change can start at any point on the cycle, but given that Vera’s theory challenges the ‘closed-canopy forest’ hypothesis, let us start at this point.

Vera’s theory proposes that as closed-canopy forests age, trees collapse, forming glades. The grasses and saplings that spring up in these glades attract species such as bison and red deer, whose grazing keeps the vegetation short and open. Slowly more glades form, expand and connect to create open grassy patches that attract herds of aurochs, horses and fallow deer, which further drive the cycle towards open grassland. However, for a whole variety of biological and non-biological reasons that we will go into in the next chapter, grazing impacts are patchy and this enables thorny bushes to establish and provide safe nurseries for animal-transported and wind-blown seeds of the larger woodland trees. As the saplings grow and gain stature, they shade out the bushes to form groves, which reduces the area available for grazing and swings the cycle back towards closed-canopy woodland.

Fig. 2: Schematic representation of Frans Vera’s theory of cyclic vegetation turnover.

(courtesy of Jeroen Helmer/ARK Nature)

Reaction to Vera’s novel theory

For many ecologists, Vera’s theory had an intuitive appeal that was amplified by witnessing evidence of his ideas in their local landscapes and the knowledge that it was being put into practice in the OVP. Others viewed it as highly speculative and not supported by evidence from the pollen record, which was dominated by the pollen of woody species. Vera had addressed this issue in his book by pointing out that grass pollen was more delicate and less likely to blow into the marshy depressions where long-term ecologists collect their sediment cores. However, in the deductive model of science, an absence of evidence is not a valid reason to support a theory – and often condemns novel thinking to the speculative edge of science. Vera’s work largely escaped this fate on account of the exciting new vision his theory and the OVP offered European conservation. It was also helped by his willingness to host visitors to explain and debate his ideas during a walk through the OVP, which is easily accessible from Amsterdam.

One scientist to visit was Professor Kathy Willis, head of a leading long-term ecology lab at the University of Oxford. As mentioned in Chapter 2, the analysis of pollen from bands in sediment cores can be dated using carbon-14 techniques, and this was central to her lab’s research. As such she was especially interested in Vera’s suggestion that the technique offered only a partial signature of past environments. In discussion they formulated a research project to test the hypothesis that naturally grazed grasslands produce little pollen (because grass flowers are eaten) and this would in part explain the rarity of grass pollen in sediment cores. She secured funding for a research student who proved that at the OVP this was indeed the case, thereby adding evidence to Vera’s assertion that the predominance of tree species in the pollen record had blinded ecologists to the possibility of wood-pasture systems. The study of phytoliths, the tiny silica particles formed within plants, has further reinforced this view.

Another test of Vera’s hypothesis is being conducted by Adrian Newton at the University of Bournemouth, not far from Vera’s original inspiration, the New Forest. Newton is an expert on the biodiversity and socio-ecological history of the Forest and is feeding all available evidence into a computer model to simulate the processes of cyclic vegetation turnover proposed by Vera. As yet the model has not supported the element of Vera’s theory that suggests that there is a key transition from closed-canopy forest to open glades and grasslands, completing the cycle of vegetation. In particular, one of the limitations of Vera’s theory is that it doesn’t really deal with the question of scale – over what area and timescale does the cycle operate?

The significance of the OVP

During the 30 years since its inception, the herds on the OVP have grown in size, and in hard winters many animals starve and die. This understandably causes concern and anger among those who care deeply about animal welfare. As a result, the OVP is increasingly referred to as a failed experiment. However, given its origins in inductive reasoning, it is perhaps better considered as a ‘nature design studio’, rather than an experiment in the formal scientific sense. The OVP has caused ecologists and conservationists to re-examine some of the fundamental tenets underpinning their science and practice. Among the most significant revelations are:

Vegetation does not necessarily succeed to high forest. In many regions of Europe it existed in the past in dynamic states caused by grazing animals and other natural factors.

The natures that Europeans have been conserving are the outcomes of millennia of human intervention. Celebrated woodlands such as Białowieża in Poland and Belarus may be the product of herbivore extinctions, rather than the last remnants of an immense primeval forest.

Versions of much older natures can be restored and recovered, alongside those of a new and novel nature.

Siberia’s Pleistocene Park

At the same time that young Dutch ecologists were unsettling European conservation with radical new ideas and practices, a young permafrost scientist was embarking on a similar journey of reassessment 12,000 kilometres away on the opposite edge of the Eurasian Plate. Sergey Zimov moved to the remote Russian frontier town of Chersky in the 1980s. The town was established to support mining and serve Cold War military installations in a region of Siberia with 30–40m-deep frozen soils (known as yedoma) cut through with ice wedges. Building on such a substrate required a technical knowledge of permafrost warming, thawing and refreezing.

An hour’s speedboat journey from Chersky, a broad bend of the Kolyma River cuts into the permafrost, creating cliffs that are great for studying the structure of the deep yedoma soils. It was the content of these soils that surprised Zimov: they smelt of ammonia, and bones of bison, horse, elk and mammoth were literally falling out of them. Walking along the muddy beach he found clusters of bones – the 10,000-year-old remnants of Pleistocene megafauna. He systematically surveyed these bones and calculated that the boggy Arctic tundra of the region once supported a rich megafauna with densities of one mammoth, five bison, 7.5 horses, fifteen reindeer, 0.25 lions and one wolf per square kilometre. The amazing revelation was that this area of Siberia was once a ‘mammoth grassland steppe’.

Zimov realised that the sudden demise of the Arctic megafauna had initiated a ‘phase shift from one stable ecological system to another’. In the absence of herbivore grazing and trampling, a new annual cycle of vegetation growth emerged that produced a rapid accumulation of permafrost, as summer growth died back and was incorporated into the frozen soils.

When the Soviet Union collapsed in 1991, most of Chersky’s inhabitants left; but, fearing wider social upheaval, Zimov remained with his young family and joined the dispersed community of subsistence fishermen. His research on permafrost meant he was well versed in climate science, and his immersion in the wilds of Siberia produced observations to suggest that the permafrost was thawing deeper each year – and with this, releasing more greenhouse gases. He realised that climate change would require scientific study across a network of Arctic research stations. As the newly constituted Russian Federation stabilised, he returned to Chersky to found the Northeast Science Station. This attracted research scientists from the US and elsewhere and Zimov used some of the income to develop an experimental project they called the Pleistocene Park – a name inspired by the film Jurassic Park.

Zimov introduced the experiment in an essay in Science published six months before Josh Donlan’s attention-grabbing Pleistocene rewilding agenda. He described two goals: to ‘determine more precisely the role that Pleistocene mammals played in maintaining their own ecosystems’; and to learn how to restore and extend Pleistocene-like grasslands to mitigate the progress and effects of global warming. In his essay, Zimov presented arguments to support the overkill hypothesis and, like Frans Vera, historic evidence of the survival of megafauna (such as bison) into the more recent past; he also noted the existence of primitive breeds that could be used to reassemble a version of the lost megafauna assembly. Inspired by his research, Zimov fenced 1,000 hectares of tundra and taiga and introduced hardy Yakutian horses, elk, musk ox and bison. In 2014, his son Nikita took over leadership of the project. A major challenge has been translocating animals to a distant region, accessible only by barge and over a winter-iced road. It has been difficult to establish herds of any size, and the idea that these few animals alone can drive a phase shift from a tundra of moss and trees back to grassland steppes may be unrealistic without mechanical intervention.

The significance of Pleistocene Park

Like the OVP, the Pleistocene Park has made a major contribution to rewilding science. In particular it has:

Contributed compelling evidence in support of the overkill hypothesis.

Revised scientific views of Arctic ecosystems. Previously it was assumed that tundra and taiga (boreal forest) ecosystems were the natural vegetation of the Arctic. We now realise that across large swathes of the Arctic they are relatively new, the outcome of a phase shift caused by the demise of megafauna herds due to hunting.

Explicitly linked climate change and rewilding science (more on this in Chapter 6).

Inspired efforts to ‘clone a mammoth’ (in reality an Asian elephant with mammoth-like traits) and with this opened up the notion of ‘de-extinction’ (more in Chapter 7).

Positioned rewilding as a natural climate solution (more in Chapter 8).

Island rewilding

Oceanic islands by virtue of their isolation have relatively simple ecosystems made up of the few vagrant species that succeeded in colonising them. Islands are, however, famous for their high proportion of unique species that evolved in such isolation and free from continental predators and competitors. Sadly, in the conservation world they are also known for the huge number of extinctions which started in the 17th century when European seafarers started to visit them regularly to stock up with wild meat, fruits and other edible plants. Although the early voyagers were responsible for the extinction of the larger and more extraordinary island species, it is the animals and plants they and later settlers introduced – or that ‘jumped ship’ – that have caused ongoing extinctions and damage to island ecosystems.

The island of Mauritius, in the Mascarene archipelago located in the Indian Ocean between 700 and 1,500 kilometres to the east of Madagascar, is one of the saddest tales of island extinctions. The dodo, which became extinct on Mauritius in 1861, has become the international symbol of extinction, but since the first arrival of Europeans 77 other indigenous species have gone extinct on Mauritius. This process is continuing, and the fight to save species on the edge of extinction was popularised by the naturalist Gerald Durrell in his 1977 book Golden Bats and Pink Pigeons. Durrell described how introduced rats and cats were predating the endemic birds, and how grazing by introduced rabbits and goats was preventing the growth of new native trees and bushes and creating a more open and degraded vegetation. His vivid accounts of the desperate plight of many species on Mauritius attracted a growing number of conservation scientists to the island, and this led to the establishment of the Mauritian Wildlife Foundation (MWF) in 1984. Together with the Mauritius National Parks and Conservation Service, the MWF embarked on a bold vision to restore the condition of two small offshore islands, Île aux Aigrettes (only 0.25 km²) and Round Island (1.69 km²), and return them to a state not seen since the arrival of Europeans in the 17th century. This was the beginning of a flagship initiative in island rewilding.

Initially, the MWF focused on reducing the direct threat to critically endangered species such as the Mauritius kestrel, echo parakeet, Mauritius fody and, of course, the golden bat and pink pigeon. Understandably, they started by eradicating the rats, feral cats, rabbits and goats: a task that was achieved in the early 1990s. These actions benefited the birds, but subsequent scientific monitoring revealed that removal of grazing by rabbits and goats ‘released’ populations of non-native and tall-growing weed species which became invasive, causing declines of native tussock-forming grasses and threatening endemic plant species such as the Mascarene Amaranth (Aerva congesta) which survived only on Round Island. The scientists realised that a herbivore was vital to the functioning of Mauritian ecosystems, but what was needed was a herbivore with the right traits, namely a substitute for the two extinct species of Mauritian giant tortoises that had co-evolved with the vegetation.

Fortunately, a species of giant tortoise survived on the atoll of Aldabra in the Seychelles and this was an ideal candidate to fulfil the functional role of the extinct species. However, with so much effort having gone into removing alien species from the island, the idea of introducing a non-native tortoise was not without opposition. Furthermore, the International Union for Conservation of Nature (IUCN), an intergovernmental body that sets global conservation standards, has very strict guidelines concerning species introductions. These state that introductions outside an endangered species’ range should only be undertaken as a last resort and when there are no opportunities for reintroduction within its range. The plan to introduce Aldabra tortoises to a different island group clearly contradicted these guidelines, but MWF and their international scientist collaborators successfully argued that taxon substitution should be considered differently – and that in the case of tortoises, worries about introduced species becoming invasive didn’t apply because they could easily be removed if they got out of hand. Furthermore, the Aldabra giant tortoise was an ideal candidate to test taxon substitution because animals for release could easily be bred in zoos, did not carry diseases that might affect other species, and could be contained in fenced enclosures where their ecological effects could be studied.

In 2000 the first four Aldabra giant tortoises were introduced to Île aux Aigrettes. At first they were kept in pens, but after botanical surveys had confirmed they had no negative impacts on native plants, another seven were introduced and they were all allowed to roam free. In 2008 a second introduction of twelve tortoises took place on Round Island to the north of Mauritius, and following subsequent introductions between 2010 and 2016 over 430 now roam the island. The tortoises have grazed out taller non-native vegetation, restoring grazing lawns and creating space for the recovery of native plant species with adaptations to withstand tortoise grazing. The reappearance of warm, tightly grazed vegetation and tortoise-scuffed earth has enabled endangered giant skinks to bounce back and become common again. Research suggests that the full benefit to the Île aux Aigrettes and Round Island ecosystems will be seen when tortoises reach densities of around 1,200 per square kilometre.

Biologist Dennis Hansen, who was closely involved with the tortoise reintroductions on Round Island, has pointed out that the concept of ‘megafauna’ often depends on context. As we have seen above, a weight threshold, for example animals that regularly achieve weights above 40kg, is widely used to define megafauna. However, in a 2009 article entitled ‘The Forgotten Megafauna’ Hansen and Mauro Galetti pointed out that context matters. They argued that the megafauna concept should be extended beyond an absolute animal size or weight to include the largest vertebrates in any given ecosystem. This is because, on a relative scale, the largest vertebrates in one ecosystem have similar ecological impacts to those in another. As they put it: ‘One ecosystem’s mesofauna [mid-sized animals] is another ecosystem’s megafauna.’ Hansen pointed out that giant tortoises, which can attain 100kg, are island giants and the largest native frugivore (fruit-eater) on oceanic islands. Up until the tortoise reintroductions on Mauritius, that title of largest living frugivore had gone to a fruit bat weighing only 0.54kg. This fact underlines the scale of megafauna downsizing on islands, which is even greater than that on continents. In response to this insight, Hansen and a team of scientists have called for action to introduce extant species of giant tortoise as taxon substitutes for extinct species on other islands, for example the Canary Islands off north-west Africa, as a means to restore and rewild these degraded ecosystems.

The significance of island rewilding

The contribution of rewilding with tortoises is more nuanced than the previous two initiatives but no less significant. These pioneer rewilding projects have:

Provided a successful trial of the concept of taxon substitution.

Made the case that taxon substitution should be treated differently in IUCN guidelines on species reintroduction and translocation.

Drawn attention to the fact that grazing is an important ecological process on islands as well as in continental ecosystems.

Reframed tortoises as mega-herbivores in the context of islands and perhaps other ecosystems.

Introduced the recovery of tortoise populations as a component of rewilding – and not only on islands.

Wolf reintroductions in the Yellowstone ecosystem

The reintroduction of wolves into the Yellowstone ecosystem was a key inspiration for the American conservationists who coined the term rewilding and the ‘cores, corridors and carnivores’ strapline they attached to their continental-scale rewilding agenda. However, in contrast to the examples above, this project originated not from the radical ideas and actions of applied scientists but from within the bureaucratic institutions of scientific nature management. Yellowstone is now cited as one of the best examples of how reintroducing carnivores can help return degraded habitats to a healthy and functioning ecosystem.

Yellowstone is famously the world’s first national park (established in 1872) and its spectacular geysers, scenery and wildlife have made it a major recreational destination. During the 1970s and 80s, ecological science gained influence in government conservation institutions, and the focus of US conservation expanded from individual species to managing the wider ecosystem. This created the impetus for a Greater Yellowstone Ecosystem with the national park at its core, containing habitat sufficient to support the population range of species such as the grizzly bear. But at this time, wolves were absent from the park, having been ‘cleaned out’ across vast swathes of North America by the mid-1900s, including the northern Rockies. Park ecologists gradually started to recognise that this absence was having detrimental impacts on the ecosystem. In particular, elk grazing was causing the decline of upland aspen woodlands and riverine cottonwoods, and in the absence of wolves, increased coyote populations resulted in intensive predation on smaller species. Back in the 1940s, Aldo Leopold, the doyen of US conservation, had proposed reintroducing wolves to Yellowstone, but the park ecologists not only presented a clear scientific rationale for not doing so – they were actually involved in the extermination of the wolves on the grounds that they wished to protect ‘more desirable’ species such as elk and deer.

A second major driver for reintroducing wolves was the 1973 Endangered Species Act. This created a federal mandate to recover grey wolf populations to a level where it could be removed from the protected species list. The north Rockies was identified as an area for recovery and the US Fish and Wildlife Service (USFW) appointed a Mountain Wolf Recovery team to develop a plan. Then followed twenty years of scientific and ecological impact studies, as well as plenty of legal wrangling, before the first 66 wolves were released in 1995. Social surveys showed that a majority of people, both in urban and rural areas, were in favour of reintroduction, with visitors to Yellowstone being particularly supportive. However, ranchers were vehemently against it, arguing that they would not be properly compensated for lost livestock, and mounted legal challenges. To overcome some of the resistance, the USFW decided to introduce a different sub-species of wolf to that which had been extirpated 70 years earlier. In so doing, they were able to class the reintroduction as a ‘non-essential experiment’ which allowed much more flexibility in the approaches they could take to manage potential conflicts with livestock farmers.

By 2005 the population of wolves in Yellowstone had reached well over 300 and the beneficial impacts on the ecosystem were clear for all to see. Not only had numbers of elk decreased, but the pattern of their grazing had changed. They avoided denser cover to lower the risk of ambush and steered clear of open areas where they could be more easily run down by predators: this led to the recovery of aspen, willow and cottonwood trees. Released from grazing, the taller growth of riverside willows led to the recovery of aquatic ecosystems. This, in turn, supported the resurgence of beavers, which had also become extinct in the region. The wolf packs also killed and displaced coyotes, allowing red foxes to recover, and it was observed that the increase in elk kills benefited a whole range of scavengers including grizzly bear, cougar, wolverine and raven.

The significance of the Yellowstone wolf introductions

The wolf reintroductions played a seminal role in the emergence of rewilding as a new conservation agenda. They were a key inspiration for Dave Foreman’s vision for rewilding North America and also for a continental wildlands project proposed in the late 1990s by Michael Soulé, John Terborgh and Reed Noss, three founders of the influential discipline of conservation biology. Their rewilding agenda was founded on three scientific premises. First, the evidence of top-down regulation of ecosystems by predators such as wolves. Second, the theory of island biogeography which demonstrated a relationship between the size of an island and the number of species. As we saw earlier, this theory predicts that as natural ecosystems become ‘islands in a sea of cultivation’ the number of species will fall to a lower equilibrium, causing local extinctions. Third, that connecting natural areas through corridors will help overcome such ‘island effects’ and create the space for wide-ranging predator populations.

More specifically, the Yellowstone wolf reintroduction:

Renewed scientific interest in the role of apex predators and top-down cascades through food webs in the assembly and functioning of ecosystems (more in Chapter 6).

Highlighted the complex biological, social and political challenges associated with predator reintroductions.

Positioned the wolf, as a species with deep and conflicting cultural connotations, as a symbol of rewilding, thereby making it political.

Aligned rewilding with wilderness concepts and the aspiration of recovery of ecosystems to a state where they would ‘look after themselves’.

Versions of rewilding

These four experiments in rewilding are commonly referred to in the scientific literature. However, progressive conservation initiatives that either adopt the label rewilding or are labelled as such, exist on most continents. They all share a new emphasis on, in the words of Rob Brewster, founder of Rewilding Australia, ‘restoring ecosystem function and resilience by reintroducing and advocating the protection of keystone species’. However, as we have already seen, this aim is expressed in different ways in different countries due to different ecological histories, cultural attitudes towards nature, and conservation traditions, among other things. In a 2016 essay in the journal Current Biology, David Nogues-Bravo and colleagues presented an initial classification of the various rewilding approaches, namely:

Trophic rewilding – they defined this as ‘restoring big wilderness areas based on the regulatory role of large predators’. This is commonly referred to as the cores, corridors and carnivores concept, and wolves and Yellowstone is the key example.

Pleistocene rewilding was defined in terms of efforts to restore the evolutionary and ecological potential of ecosystems which were lost through the demise of megafauna 10–15,000 years ago, through introducing relatives or functional equivalents of extinct species. The Pleistocene Park is the only current example of this type.

Translocation rewilding – they defined this as actions that ‘seek to restore dysfunctional ecological processes via species reintroduction’, for which island tortoise rewilding is a key example. A different version of this is evident in South America, where the focus is on ‘refaunation’, the technical term for reintroducing larger species such as giant anteater, tapir, peccary and jaguar which have been wiped out from regions by hunting. The Iberá project in Argentina is the key example (see p. 115).

Passive rewilding is a fourth common category and refers to the release of ecological processes through reducing human control of landscapes. This is a desired endpoint of the four examples described above but it is also happening spontaneously in many regions of the world through farmers abandoning the cultivation of marginal land and traditional herding practices.

Many practical rewilders worry that definitions of rewilding formulated by academic experts will constrain their ability to innovate and experiment with new approaches to conservation. They fear that international conservation policy-makers will use such definitions to specify what rewilding should or shouldn’t be, and how it should be practised. They have a point. As we will discuss later in the book, practical rewilders are designing rewilding approaches that could help solve pressing social and environmental problems such as rural climate change, land abandonment, rural depopulation and the growing risk of catastrophic flooding and wildfires. Such innovation is adding to the diversity of practical rewilding and argues against trying to put it into tidy boxes too soon.

5

WILD NATURE – CASCADES, SPACES, NETWORKS AND ENGINEERS

At its core, rewilding is ecological restoration that seeks to learn and take inspiration from ecological histories to set a new ambition for conservation in the 21st century. It resembles the discipline of restoration ecology but differs in ethos and focus. Rewilding is not about turning back the clock and restoring damaged ecosystems to an arbitrary past baseline. Rather, it is about restoring networks of interactions between communities of organisms and their physical environment, along with the ecological processes that emerge from these interactions. It is more open-ended and relaxed about ecological novelty. It embraces the view that there is no way back for ecosystems and that, as ecological interactions and processes recover, ecosystems will take on new forms. These may evoke the past, but they will be different. Many rewilders aspire to ‘upgrade’ ecosystems to initiate wider ecological recovery – but in ways that will help steer societies towards more sustainable and liveable futures.

From this perspective, rewilding can be understood as a form of ecological engineering which seeks to undo some of the historic engineering of landscapes described in the second part of Chapter 3. Succeeding in this endeavour requires a thorough understanding of ecosystem architectures and ecological processes. As long ago as 1949, Charles Elton called for a unifying theory to explain the assembly of ecological communities and ecosystem functions. This has remained elusive. Indeed, in the late 1970s Richard Southwood, another major figure in ecology, concluded that, such is the complexity of ecosystems, no single theory can explain the patterns of diversity in nature and we should therefore develop a suite of complementary theories.

This is the approach taken in rewilding science. In this chapter we will take a deeper dive into three theories that are coming to structure aspects of rewilding science and guide the design of rewilding initiatives. These are: trophic cascade theory; ‘landscapes of fear’; and a newer theory called ecospace, which connects the biological and physical components of ecosystems. Along the way we will clarify some of the ecological jargon that peppers the rewilding literature.

Trophic cascades

Trophic cascade theory has emerged as one of the key conceptual resources in rewilding science. The theory seeks to understand interactions between organisms through the lens of food chains. It investigates how the presence or absence of interactions (for example between predators and prey) affects the complexity and structure of the ecological system, and the ecosystem processes (e.g. decomposition and nutrient cycling) that arise from chemical, physical and biological interactions between the living and non-living components of the environment.

Three American ecologists, Nelson Hairston, Frederick E. Smith and Lawrence B. Slobodkin, introduced the theory in the 1960s, but the growing number of rewilding projects is prompting scientists to extend the theory. The term ‘trophic’ refers to nutritional (food) resources, and the concept has traditionally been expressed as a series of levels with predators at the top, then herbivores, followed by primary producers (such as plants). Whereas ‘cascade’ implies (and initially referred to) top-down effects, it now refers to effects that cascade through networks in multiple directions. By way of example, the reintroduction of wolves to Yellowstone described in Chapter 4 is a classic case of a top-down trophic cascade. However, when we consider a large herbivore such as the bison, the relationship between trophic layers becomes more intertwined and extends into a complex network of trophic interactions.

Jens-Christian Svenning, who heads the Centre for Biodiversity Dynamics in a Changing World at Aarhus University in Denmark, is a leading contributor to trophic cascade theory and its application to rewilding. In a key 2016 paper entitled ‘Science for a wilder Anthropocene: Synthesis and future directions for trophic rewilding research’, Svenning and colleagues broke from the tradition of viewing only carnivores as apex consumers. Although large carnivores sit above large herbivores (which they eat) in classic trophic hierarchies, the team noted that mega-herbivores are at the apex of complex cascading effects via food consumption (grazing) and production (in their dung and bodies), and some herbivores (e.g. elephant, rhino) are only weakly affected by top-down predation. This insight was a key theme of Shaun Carroll’s book and award-winning film The Serengeti Rules. By complicating the traditional pyramidal representation of trophic hierarchy, scientists have given form to the idea of interacting trophic webs with functional species creating cascading effects in different directions through the networks.

Conservation science is full of species metaphors: flagship, keystone and umbrella species are among the most common. The term ‘keystone species’ is commonly used to refer to species that have a large effect on their ecosystem and whose absence would change that system. While the term is widely used in the rewilding literature, many scientists are now adopting the term ‘functional species’ in preference. This is because the keystone metaphor, which suggests a central, apex species locking an ecosystem together, is not so well suited to modern understandings of ecosystems as networks of organisms, some of which have a disproportionately large effect on ecosystem structure and on processes such as decomposition or nutrient cycling.

Functional species that produce significant cascade effects through modifying habitats are termed ecosystem engineers. One of the most famous, and an icon of rewilding in western Europe and North America, is the beaver. Beavers are able to transform ditches running through agricultural fields into wetland paradises full of mosses, plants, insects, amphibians, birds and mammals. Beavers build dams, lodges and channels to create a watery environment full of willows and aquatic plants which they feed on. They gnaw and fell riverside trees for their engineering projects, which produces complex and dynamic wetland and river systems. The diverse plants in these systems capture sunlight and draw up nutrients which support and cascade through an ecological web of fish, amphibians, birds, insects and other life. The wetland systems that beavers engineer lead to the recovery of ecological processes such as filtration and water management which produce valuable services to society in the form of better water quality and natural flood management. In Europe, generating value for both people and nature is a key rewilding principle, and this explains why the beaver has become something of an ‘ambassador’ species for rewilding.

Landscapes of fear

In 2010, a team of American ecologists lead by John Laundré published a paper with the intriguing title ‘Landscapes of Fear: Ecological implications of being afraid’. The argued that fear – caused by the anticipation or awareness of danger – was felt by animals and as a result they would avoid places where they lacked a clear sight of and/or the opportunities to flee predators. Such locations might be steep valleys, waterlogged areas or even tree falls in forests. They drew on the example of wolves and elk (mentioned in Chapter 3) and a long-term study of the interactions between puma, mule deer and vegetation structure which showed that the deer avoided areas with higher predation risk.

Introducing fear into ecology extended understanding of the mechanisms that produce trophic cascades beyond simple predation and consumption models. It has also generated more attention to the cascade effects of interactions between large and mid-sized predators (also known as meso-predators) such as foxes, cats and martens. These species can all fall prey to larger carnivores, and research shows that they ‘hang around less’ when wolves, pumas, lynx and the like are in the vicinity. This reduces their own predation of small mammals, amphibians and birds and their eggs. Indeed, when large predators are absent, meso-predators can become super-predators and cause significant reductions in small species, with cascading effects on populations of other predatory species (e.g. storks and hawks) and processes such as grazing, seed dispersal and pest control.

Fear may not be the only factor involved in producing indirect trophic cascades and creating variation in grazing and associated ecological processes across landscapes. Irritation may have similar effects. Newly attuned to landscape of fear ideas, rewilding practitioners are asking whether the migration of free-roaming herds of bison, cattle and horses to higher altitudes during the summer months is motivated by a desire to avoid biting insects. Such observations underline the newer multi-directional understanding of trophic cascades.

Ecospace – a new way of thinking about niche

Trophic cascade theory helps us to understand and, to an extent, predict the effects of the loss and reintroduction of species on the ecological web of life. The concept of ‘ecospace’ offers a complementary framework for understanding how local conditions determine the identity and diversity of organisms and interactions in ecosystems. This is an important aspect of the rewilding science picture, not least because it makes the connection between the biotic (living) and abiotic components of the environment.

The importance of local abiotic conditions is illustrated by the case of the black poplar, a once-common European riverside tree that is nowadays critically endangered in many west European countries. When a pioneer Dutch rewilding project re-excavated old river channels, hundreds of black poplar seedlings popped up on their margins. Ecologists realised that in order to germinate, the seeds of black poplar need the warm, lapping and frothy water that occurs in late summer along shallow river margins. This is a great example of an ephemeral ecospace (or micro-habitat) that emerges from physical interactions between sunlight and the movement and chemistry of water.

In a 2016 scientific paper titled ‘Ecospace: a unified framework for understanding variation in terrestrial biodiversity’, Ane Kirstine Brunbjerg and Rasmus Ejrnaes of Aarhus University sought to integrate the biotic and abiotic in a single concept and provide the unified theory that Richard Southwood had thought too ambitious. Brunbjerg and Ejrnaes’ concept of ecospace – shorthand for ecological space – arises from a reinterpretation of Elton and Southwood’s foundational work. This older work gave rise to the concepts of habitat and niche, which have had a strong and enduring influence on conservation thinking and policy. The notion of a habitat or niche focuses on the needs of organisms. Traditional conservation categorises, protects and manages habitats that provide the environmental conditions needed by a species or a set of species. Ecospace, in contrast, focuses on the conditions and resources that enable organisms to develop. This might sound like splitting hairs, but the difference is significant. This is because, rather than providing a framework for understanding ‘what is’, ecospace offers a framework for understanding ‘what could become’ – the processes of coming into existence or becoming rare and extinct. Put another way, the concept of habitat enables us to provide, through protection and management, for the needs of the nature we currently have. The concept of ecospace offers a blueprint for actions that will help nature recover and for ecosystems to re-expand.

The natural world is full of gradients: differences in temperature, sunlight and moisture, soil pH, nutrient availability, water turbidity, substrate stability – the list is almost endless. These gradients combine in different ways, in different places and at different times to produce the conditions and resources where plants can grow and where animals can rest, feed, breed and move. Sets of conditions that consistently emerge in time and space provide possibilities for species to evolve and life to flourish. Some are ephemeral and highly local, such as the lapping water creating the conditions for black poplar germination. Other sets of conditions are more stable and widespread, such as nutrient-poor alkaline soils which provide the conditions and resources for specialist herbs to flourish but not tall woody vegetation. Yet other sets of conditions emerge periodically at particular times and support migratory or highly mobile species. The short Arctic summers with 24 hours of sunlight, berry-laden bushes, and the muddy margins of autumn pools are all examples of seasonal ecospaces.

Human engineering and management of landscapes and agriculture have massively reduced and altered the variety and patterns of the abiotic sets of conditions and resources. A goal of rewilding is to release landscapes from engineered structures and agricultural inputs so that the variety and abundance of ecospaces reappears. River rewilding is a great example of ecospace thinking. In many lowland regions, rivers that naturally braided and formed backwaters, oxbow lakes and gravel banks have been engineered into channels to make them navigable, and to drain waterlogged land and manage flood flows. Concentrating river flows increases their power, which washes away gravels, increases sediment loads and deepens channels. The river system becomes simpler, with a few dominant ecospaces. They are still freshwater habitats supporting important plant, invertebrate, fish and bird communities, but the range of conditions is limited – and with this the variety and abundance of life decreases. Recreating ‘living rivers’ through the removal of structures such as bank piling, weirs and drainage systems, and re-excavating filled-in or silted-up braids and backwaters restores gradients in river flow and patterns of scouring and sediment deposition.

The Dutch have been particularly progressive in this area. Rewilding organisations such as ARK Nature have worked with brick and aggregate companies to design schemes that reconnect rivers with their floodplains (more in Chapter 7). The reappearance of gravel riverbeds, banks and pools creates a myriad of ecospaces – from the micro- to the meso-scales. For example, the gaps among the gravels provide a foothold for aquatic invertebrates, shallow gravels produce rippling, oxygenating the water and creating ideal conditions for fish to spawn, and seasonally dry sand and gravel provide nesting sites for plovers (a small wading bird) and the growing conditions for annual and riverine plants. In addition, dynamic rivers lead to the formation of sand dunes and gravel banks that create permeable dams which filter nutrients from the water and create the conditions for localised ecosystems of specialist aquatic plants and animals to appear.

The above account could equally be written in the language of habitat and niche – removing river engineering restores gravel habitats that provide niches for invertebrates. However, the notion of biotic expansion is central to the concept of ecospace (and rewilding of course). This considers how the physical ecospaces create the basis for the accumulation and diversification of biological life and formation of organic structures. For instance, in the earlier example, shallow gravels provide spawning grounds for salmon which in turn provide a food resource for bears and eagles. The bears and eagles may only consume part of the salmon, leaving a local carrion ecospace that provides resources for scavengers and flies and may also add nutrients to the ground on which it lies.

The insight that plants and animals create the conditions and resources for other animals to live in is not new, of course: it is part of the notion of food webs, which have long been researched and discussed. However, the concept of ecospace invites ecologists and conservationists to think more deeply about how the accumulation of plant and animal matter creates the conditions for ecosystems to expand and diversify. For example, how the stump of a beaver-felled tree provides the conditions for a bracket fungus to grow, and how the dung of cattle creates temporary ecospaces for dung beetles which roll it into their burrows, increasing soil organic matter and nutrient resources in the wider grassland ecospace.

The expansion of ecospaces creates webs of trophic interactions as well as interactions between organic life and inorganic processes such as nutrient cycling (see next chapter). The reason why this book has given so much profile to herbivores is because we now realise that they play an inordinately large role in the expansion of ecospace and the abundance of plant and animal life in a region. Herbivores expand ecospace in a number of ways. The provision of dung is one. A second is their bodies, which support a rich ecosystem of micro-organisms and parasites and, as carcasses, create the conditions for multiple life forms: from bacteria to maggots, beetles and foxes. A third is their grazing, trampling and wallowing behaviours, which diversify vegetation and physical substrates. For example, in the summer a horse herd may scuff the ground, creating conditions for lizards to flourish in the warm, bare earth; and in the winter the horses may gnaw bark, which the tree repairs with callouses that provide shelter for spiders, which provide food for woodland birds. A fourth way in which herbivores contribute to ecospace expansion is through the transport of species from one area to another, for example seeds caught in their fur or passing through their digestive tract. In summary, large herbivores play an outsized role in ecosystems, and their decline as wild species millennia ago and more recently as working farm and grazing animals has led to a shrinking of ecosystem complexity.

Species pools and ecosystem expansion

The extent and rate by which ecospace can re-expand depends on the ‘pools of species’ that are present. A bracket fungus will only grow on a tree stump if there is another spore-producing fungus in the vicinity. A large herbivore carcass will expand scavenger ecospaces more if hyenas (in Africa) and wild boar (in Europe) are around to tear through thick hide and make the resources available for less powerful scavengers. As an ecological engineering practice, rewilding introduces functional species missing from local species pools – such as the giant tortoises on Mauritius and the ‘de-domesticated’ horses and cattle in the Dutch delta. However, it is impractical to reintroduce the myriad smaller species that create ecosystem complexity, and for this reason the success of rewilding projects is dependent on the pools of smaller species present in the wider landscape.

Some conservation professionals complain that rewilding is being presented as a new and better approach to conservation, implying that past conservation efforts have been somehow sub-optimal. The ecospace concept helps position rewilding as a complementary approach that expands the scope of traditional conservation with its focus on protecting a representative range of habitats and their associated species. This established approach has achieved considerable success in protecting and recovering species pools and maintaining a degree of connectivity across landscapes. The science of rewilding – and in particular the concepts of ecospace and trophic cascade – allow scientists to design interventions that will enable these species pools to expand and reassemble as webs of ecological interactions. The ‘Protect the best, rewild the rest’ strapline expresses this positive interplay between traditional ‘compositionalist’ forms of conservation and the newer ‘functionalist’ approach of rewilding.

Rewilding vis-à-vis ecological restoration

The question of whether rewilding is just a repackaging of old and established ideas and practices is actively debated in the scientific literature. In 2018, an international team of 37 scientists published an article arguing that the term ‘rewilding’ should be rejected, and urging the use of ‘restoration’ for all formal scientific, policy and conservation discourse. They pointed out, correctly, that rewilding has many definitions, e.g. trophic rewilding, Pleistocene rewilding, island rewilding and passive rewilding. The authors argued that this renders the term unsuited for rigorous scientific use and translation into policy. Furthermore, they contended that there is little difference between the science and practice of rewilding and that of the established discipline of restoration ecology, and that we should therefore revert to that term.

To an extent they have a point. Rewilding is a form of restoration ecology, but not all restoration ecology is rewilding. As discussed in the last chapter, rewilding science is ecology-led but embraces and blends theory and insights from a range of disciplines. In addition, the practice of rewilding is more innovative and radical than anything that has yet emerged from ‘classical’ restoration ecology. In Table 2 we have identified some of the key differences between restoration ecology, as currently conceived, and rewilding. Our view is that rewilding signifies a new departure for restoration ecology – one that is more multi-disciplinary, prioritises systems rather than linear thinking, and aims to create the conditions for ecosystems to recover rather than restore ecosystems to a template specified by arbitrary past baselines.

Put another way, restoration ecology becomes rewilding when it moves beyond habitat restoration and species reintroductions to ‘reset’ the conditions for ecosystems to re-expand and function with decreasing human intervention. This may lead to ecosystems that evoke past ecosystems, but they are likely to be different or ‘novel ecosystems’ in the jargon. Rewilders are relaxed about this, whereas restoration ecologists like to work to templates. Importantly, rewilding has a strong, though not exclusive, focus on restoring the ‘big stuff’, believing that if megafauna are once again part of ecosystems, the ‘small stuff’ will mostly look after itself.

Table 2: Rewilding and restoration ecology compared.

Aspect | Restoration ecology | Rewilding
Disciplinary focus | Ecology | Ecology-led but multidisciplinary
Logic | Linear thinking | Systems thinking
Restoration baseline | Pre-colonial, pre-industrial | Multiple, since late Pleistocene
Restoration aim | Habitat composition and species populations | Ecosystem structure, function and processes
Restoration outcome | Specified and managed | Uncertain and unfolding
Taxon focus | Plants, priority species | Functional species and megafauna
Ecosystem focus | Components and assemblies | Interactions and dynamics (biotic and abiotic)
Landscape focus | Connectivity | Dispersal and disturbance
Level of intervention | High, continuous | Create conditions for ‘self-willed’ ecosystems
Monitoring focus | Species composition, status and distribution | Trophic complexity, natural disturbance and connectivity
Ethos | Defensive, protectionist | Offensive, pragmatic, innovative
Nature and people | Usually separate | Aspiration to integrate

Restoring complex ecosystems: a guide

During 2018 a group of sixteen ecological scientists from across Europe met in Leipzig, Germany to work through developments in rewilding and ecology and create a framework that could guide rewilding research and practical action. Their framework, published in the prestigious journal Science under the title ‘Rewilding Complex Ecosystems’, boiled the science of ecological recovery down into three key processes: ‘trophic complexity’, ‘stochastic [random] disturbance’ and ‘dispersal’. They argued that the state of any ecosystem can be plotted in three-dimensional space, where each process is represented as an axis. The volume of the central pyramid provides a proxy (indication) of the richness, diversity and resilience of a present ecosystem (Figure 3). This effectively converts the nuance of advances in ecosystem science into a lens for asking important new questions about the state of nature and the areas we protect: how complex are the trophic interactions, how easy is it for organisms to disperse, and how frequent are natural disturbances? When these questions are asked of today’s landscapes and even our protected natural areas, the answer more often than not is a salutary ‘not very’.

Fig. 3. The three dimensions of ecosystem recovery.

Redrawn from Perino et al., ‘Rewilding Complex Ecosystems’, Science, 2019

Practical rewilding involves actions that aim to move up these scales within the constraints of what is feasible. We will discuss these in more detail in Chapter 8, but here it is relevant to note that most rewilding initiatives are practical experiments in ecological recovery where outcomes are allowed to unfold. As yet there has been little scientific research to build a more detailed evidence base that can underpin efforts to move up these scales in an effective manner. For example, we do not know whether it is important to move up all scales at the same time, or whether action to move up one scale results in movement up the others. The science of ‘rewiring’ ecosystems and ‘kick-starting’ ecosystem upgrading and the recovery of ecological processes is still in its infancy.

6

EARTH SYSTEM IMPACTS

In recent decades, Earth system science has emerged as a new discipline seeking to understand our planet as a dynamic system of interacting parts that combine to form the conditions for life. The top-level sub-systems or ‘spheres’ of Earth are the geosphere (the solid parts – land and rock), the atmosphere (the layer of gas around the Earth), the hydrosphere (water in all its forms – liquid, solid or vapour), and the biosphere (the parts of the previous three where organisms live). The Sun and geothermal heat power processes such as evaporation, erosion and photosynthesis that all connect to form great cycles which transport carbon, oxygen, hydrogen, nitrogen and other materials, essential for life to flourish, through and between the different spheres.

The various life and Earth science disciplines have long studied different aspects of the system, but the vision of a holistic super-discipline emerged only in the 1980s, when NASA adopted the term ‘Earth system science’ to structure their future research. This was at a time when advances in remote sensing technology, expanding global databases, more powerful computers and sophisticated computer models created the possibility to integrate processes and cycles in interlinked Earth system models. The need to understand and respond to climate change – an emergent property* of system interactions – has raised the importance of Earth system science and also made visible the impacts of human activities on our planetary systems. Such is the scale and impact of the Anthroposphere (human civilisation) on Earth systems that the term ‘Anthropocene’ has been coined to denote a new geological epoch.

There has been a lot of debate on the starting date for the Anthropocene epoch. As a geological concept, the transition from one epoch to another must be visible in rock layers. It is widely recognised that early humans had major impacts on the Earth’s system when they started using fire in the early Pleistocene epoch and when their activities led to the extinction of about half of all large-bodied mammals worldwide. Indeed, as we will see later in this chapter, a growing body of evidence suggests that megafauna extinctions led to a first anthropogenic global warming. However, the effects of fire and megafauna collapse were not evenly distributed. Both resulted from a series of events on various continents and at different times, and so they lack the precision necessary for an Anthropocene marker (technically called a Global Boundary Stratotype Section and Point (GSSP) marker). While the exact start date for the ‘modern’ Anthropocene is still to be decided, experts believe it should be between 1945 (the first atomic bomb test at Alamogordo, New Mexico) and 1965, after multiple atomic bombs had been detonated. Radioactivity from the bombs can be witnessed as a ‘golden spike’ of the plutonium-239 isotope in ice and rock deposits across the globe and is particularly evident between 30 and 60 degrees north of the equator, where fallout from atomic bombs was at its highest.

The new knowledge on the interactions between megafauna, vegetation and ecosystem structure, explored in the preceding chapters, is prompting scientists to ask whether the demise of the megafauna had Earth system effects resulting from changes in the function of ecosystems at different scales. If so, the scientists hypothesise, could rewilding and its ability to restore these processes be part of the effort to create a sustainable and more vibrant Anthropocene? This new ‘big picture’ view of rewilding science is all based on modelling and still somewhat speculative, but it does present a fascinating and eye-opening insight into the potential for natural processes to solve some of the biggest challenges facing our planet. We explore these solutions further in Chapter 8, but now we will dig deeper into the links between Earth system science and rewilding science.

Global nutrient transport in the world of giants

The Oxford Ecosystem Lab led by Professor Yadvinder Malhi is a leading centre of research on ecosystem function and how this interacts with global atmospheric change and anthropogenic activity. In March 2014, it organised a landmark international workshop on megafauna and ecosystem function with the purpose of consolidating ‘understandings of changes in biosphere function since the Late Pleistocene and of the functioning of contemporary ecosystems, as well as offering a rationale and framework for scientifically informed restoration of megafaunal function where possible and appropriate’.

Chris Doughty was a young researcher in the lab who, in the run-up to the workshop, published a paper in Nature Geoscience exploring the impact of megafauna on the nutrient biochemistry of the Amazon. He followed this up with two papers on the role of animals in global nutrient cycling and presented evidence that megafauna downgrading had severely constrained the flow of nutrients across continents and between the oceans, freshwaters and land. Doughty’s ambitious and exploratory research tells a story that is redefining how we think about the biosphere.

Nutrients are essential for growth and, as every farmer and gardener knows, nitrogen and phosphorus promote plant growth. This is because these elements are necessary for the creation of cell membranes and DNA, and for chemicals that drive cell processes. The elements are also needed for bone and teeth formation in animals. Plants take up these nutrients from the soil in the form of ions,† and are what we call primary producers: via photosynthesis they are able to convert sunlight energy into living material. Plants are the ‘powerplants’ of the biosphere. In the marine and freshwater systems, algae and phytoplankton do the same job and extract nutrients diluted in the water. For life to flourish, these nutrients need to be constantly replenished – and thisis where megafauna, birds and fish come in.

Animal digestion increases the decomposition of plant and animal matter and, via dung, releases nutrients back into the ecosystem faster than other types of decomposition. Cowpats and other forms of herbivore dung are rich in nitrogen, phosphorus and potassium, which worms, beetles and other invertebrates pull down into the soil, completing the nutrient cycle. In marine systems, phytoplankton are eaten by small animals which are eaten by larger fish, birds, whales and so on, all of which defecate and return the nutrients to the sea or deposit them on land. As we move up the food chain, the bigger animals tend to have slower digestive systems and move over larger distances. Doughty reasoned that they must therefore transport nutrients and spread them from nutrient-rich to nutrient-poor areas.

With the help of Malhi, Doughty developed a computer model to explore the proposition that megafauna extinctions and the massive historic declines in whales and anadromous fish (those that breed in freshwater but mostly live at sea) had reduced the transport of nutrients, with effects on the global nutrient cycle. This involved developing a mathematical equation incorporating data for selected species on their body size, food consumption and food passage (defecation) rates along with data on their day-range, historical and present-day distributions and predicted numbers. This information can be used to calculate what is called a ‘step-size’ for each animal. They then fed this data into a model that assigns nutrient values to grid squares on a map, and by comparing present-day maps of nutrient availability with those predicted by past distributions and numbers of nutrient-excreting megafauna, they were able to model the change in nutrient fluxes and flows.

Their first model focused on Amazonia, where there is much evidence showing that phosphorus availability is the key nutrient limiting tree growth in many forests. Erosion in the Andes mountains releases phosphorus into local soils that are flushed down tributaries into the floodplain of the Amazon river. The models showed that the lateral (sideways) movement of this nutrient into the forest interior declined by 98 per cent after megafauna went extinct. They predicted that mega-herbivores such as gomphotheres and giant ground sloths would have transported 50 per cent more phosphorus into the Amazonian interior than is the case today. In short, the demise of the megafauna 8–10,000 years ago broke the nutrient connections between the floodplains and other parts of the Amazon basin.

Subsequently Doughty and Malhi developed more sophisticated models that incorporate nutrient-diffusion capacity of whales, seabirds and anadromous fish. Scientists estimate that 10–15,000 years ago our planet had ten times more whales, twenty times more anadromous fish, twice as many seabirds, and ten times more large herbivores. With such figures, their models generated the first evidence that declines in marine life had affected nutrient availability in the seas but also on land. The models indicate major changes in ocean nutrient cycling. For example, they suggest that: i) historically, anadromous fish may have moved 140 million kg of phosphorus per kilometre per year up rivers from the sea, compared to approximately 5.6 million kg today; and ii) that before the onset of commercial whaling, the stirring up of nutrients from the ocean floor by whales moved 375 million kg of phosphorus to the surface each year. Today the figure is just 82.5 million kg.

Based on their models, Doughty and colleagues proposed an interlinked system of nutrient transport and recycling on our planet (past and present) and introduced the analogy of nutrient arteries, where megafauna dispersal and migration routes transport nutrients from areas of high concentration (equivalent to the heart) into the land and freshwater (the body).

These animal-mediated nutrient flows operate at more local scales and enrich ecosystems. For example, moose graze aquatic vegetation and move nitrogen into riverside areas, promoting taller vegetation growth. Hippos move nutrients the other way from bankside areas into lake and river systems. In South Africa’s Kruger National Park, elephants and rhinos move nutrients between nutrient-rich and nutrient-poor areas, and it has been estimated that if elephants disappeared from the park, the distribution of nutrients would decline by about a half.

As well as modelling the Earth system impacts of megafauna declines, this research added the component of accelerated nutrient release, recycling and distribution to rewilding science. In Chapter 5, we discussed the three axes of rewilding complex ecosystems, namely recovering trophic complexity, disturbance and dispersal. We now understand that animal dispersal and nutrient dispersal are one and the same, and this interacts with trophic complexity and disturbance. In our increasingly urbanised and complex landscapes, restoring dispersal is a challenge; but there are many opportunities to improve things, for example removing unnecessary dams and weirs from rivers to restore anadromous fish migrations, reconnecting rivers with their floodplains, installing ‘ecoducts’ across highways, and removing fences to enable wildlife to move between areas and, in particular, to allow seasonal movements between mountains and their lowland valleys.

Seed dispersal

It was not only nutrients that the extinct megaherbivores distributed – they were also big dispersers of tree species. Indeed, many trees, especially those in the tropics, evolved big juicy fruits to attract mobile megafauna. Some of these we know well: species such as guava, jackfruit and avocado are all legacies of past megafauna which humans may have saved through cultivation. Previously, forest ecologists were puzzled by the fruit and seed characteristic of many tree species, which seemed to make no sense in present-day ecosystems. One of these was Dan Janzen from the University of Pennsylvania, who in 1982 teamed up with Paul Martin (who we met in Chapter 3) to argue that the mystery disappears when these tree traits are interpreted in the light of the extinct Pleistocene megafauna. To make his point, Janzen reconstructed the fruiting of a tropical palm (Scheelea rostrata) as it might have been 12,000 years ago. The palm produces yellow egg-sized drupes (the technical term for soft seeds protected in a hard wall and fleshy outer part) in the thousands. Janzen imagined the fruit fall attracting a herd of gomphotheres which consumed around 5,000 drupes a day. The hard nut wall protected the seed from the gomphotheres’ massive molars, such that most were excreted in their dung and distributed along trails between palm groves and in gomphothere grazing areas. Agoutis (a guinea pig-like rodent) and peccaries (a pig relative) fed on the nut-rich dung and chewed and buried some for a later day. Some of these scarified nuts were forgotten and germinated to grow into new palms. In this way palm seeds were distributed away from their parent trees.

When the gomphotheres and the ground sloths, glyptodonts and equids, which also fed on the drupes, were hunted to extinction, the palms kept on fruiting. But the agoutis and peccaries were quickly satiated and, as the drupe pulp rotted, specialist insect species laid eggs in the seeds, which were destroyed by their larvae. The bulk of the seeds perished directly below the parent palm, and those that managed to germinate were shaded out by the parent. Slowly the distribution of the Scheelea palm shrank until it now survives only in micro-habitats where conditions are so favourable that a few seeds grow into adult palms.

Janzen describes how this story of lost megafauna prompted ecologists studying plant evolution to expand their thinking. Researchers had previously regarded the nut wall to be an adaptive response to the drilling abilities of the insect pest larvae: they had not considered the possibility that its thickness could be an adaptation to the crushing force of a gomphothere’s molars. Researchers had also assumed that the fleshy outer layer of the drupe had evolved to provide rodents with enough food to make it not worth their effort to tackle the hard nut. They had overlooked the possibility that it had evolved to attract agoutis and peccaries to the scattered dung piles of gomphotheres which, due to the animal’s poor digestion, would still have been full of partially digested drupes.

Prior to Janzen and Martin’s paper, most plant ecologists had assumed that palms and trees were co-evolved with the forest ecosystem where they were found. They had not considered the possibility that many could be anachronisms for which interactions with present-day animals may hardly exist. The realisation that large-fruited trees indicated historic co-evolution with mega-herbivores – animals that would have affected vegetation structure, created open areas and provided nutrient ‘arteries’ – unsettles the widely held assumption that rainforests are pristine natural kingdoms unaffected by human activity. Increasingly, scientists understand these ecosystems as the result of human-caused megafauna extinctions and the ongoing process of defaunation, largely caused by over-hunting, which has continued since. Some of the functional roles of lost megafauna may have been replaced by domestic species, for example extensive cattle ranching in Brazil’s Pantanal ecosystem has maintained a more open forest structure.

These scientific advances raise the question of how to respond. Early in his career, Mauro Galetti, a renowned Brazilian ecologist who specialises in the ecosystem effects of species loss, succinctly framed the question in rewilding terms with reference to the vast Cerrado biome located to the south of the Amazon. He asked: ‘What do we want to preserve? The Cerrado as it is today, with an incomplete complement of fauna that is difficult to manage and full of vague niches, which is a direct reflection of the great wave of extinction at the beginning of the Holocene, or try to recreate an ecosystem that co-developed over millions of years possessing a great diversity and biomass of mega-herbivores?’

The ecological impacts of megafauna extinctions and the reduction in small herbivore numbers have been known for about 30 years, and newer research is also revealing Earth-system effects. Fifteen years ago, scientists started calling for experiments to explore the effects of restoring large herbivores and fruit-eaters, but these rewilding proposals appear too radical and have not yet gained traction with government research and conservation agencies in countries where tropical forests occur. However, in the context of the climate emergency, research on the climate impacts of megafauna may strengthen the case for large-scale rewilding experiments in other regions of the planet.

The first human-induced global warming

This is the sub-title of another provocative paper by Chris Doughty. He and his co-authors showed that the historic extinction of mammoths in Alaska and the Yukon removed grazing from the system, leading to an increase in birch trees and the shift from boreal (sub-Arctic) grasslands to forests. This would have changed surface albedo, causing warming in Siberia and Beringia by 0.2–1°C.

The albedo effect is an important variable in models of global warming. It refers to the proportion of sunlight and radiation that is reflected by the Earth’s surface. Put simply, snow reflects winter sunlight which makes the planet cooler; darker forests absorb more of the winter sunlight, making it relatively warmer. Arctic researchers are paying increased attention to the effects of defaunation and trophic downgrading on Arctic ecosystems in part because the new dating techniques described in Chapter 2 enable them to do so, but also because climate models predict that global warming will be faster and more pronounced in the Arctic. Models predict that some regions of the Arctic could increase by 4°C compared to the global 2°C average. Understanding how today’s Arctic ecosystems have formed and may react and contribute to global warming is an urgent research priority. Unfortunately, the news does not look good. Thawing permafrost will release huge amounts of carbon and methane at a time when countries are trying to cut emissions and decarbonise economies. Arctic rewilding could offer a natural climate solution to reduce permafrost thawing and Arctic greenhouse emissions.

In Chapter 4, we briefly introduced Sergey Zimov’s research on the implications of the historic collapse of the mammoth steppe for contemporary climate policy, and the Pleistocene Park experiment he and his son Nikita have underway to test whether a grassland system could be recreated. Scientific support of Zimov’s proposition that large areas of the Arctic were open steppe systems is growing. In 2014, an international group of 52 scientists published a very well-evidenced article showing that in the late Holocene, herbaceous flowering plants and grasses dominated the vegetation of the Arctic, which became wetter with bog and tree vegetation when the megafauna disappeared. Their study deployed eDNA‡ techniques to analyse permafrost soil samples. Animals and plants leave fragments of their DNA in soil which can be reassembled and compared to reference collections using modern computational techniques. The technique works particularly well in permafrost because freezing reduces movement of eDNA between strata. The authors suggested that the dominance of herbaceous plants, which are richer in nutrients than grasses, could explain why these cold systems could support such large numbers of herbivores. However, this aspect needs further research because just as the pollen record is biased towards woody species, eDNA is better at picking up herbaceous plants than grasses.

With regard to the Earth’s climate system and the albedo effect, what matters is the build-up of waterlogged peaty soils after the extinction of megafauna. In the absence of herbivores, the cycle of summer vegetation dying and becoming waterlogged with winter snow leads to an accumulation of organic-rich soils which freeze to create permafrost. In some regions, these frozen soils accumulate to significant depths – 30–40m in the north-east of Siberia – and are cut through with huge ice wedges. Now that the climate is warming, a nasty negative feedback loop is kicking in. Warmer summers extend the depth of permafrost thawing (known as the active layer) and wetter autumns bring deeper snow earlier in the winter that provides a degree of insulation. At some point the depth of the active layer exceeds the depth at which it is refrozen each winter, such that summer thawing penetrates deeper each year. As the permafrost thaws, soil microbes become active and release ancient carbon stored in the soil into the atmosphere, and ice wedges collapse, forming thermokarst lakes where microbes release methane – a potent greenhouse gas. The Arctic permafrost is estimated to contain about 40 per cent of all terrestrial carbon, with a major concentration in the deep yedoma soils of north-east Siberia and Alaska. Models suggest that 5–15 per cent of this carbon could be released into the atmosphere this century and as a result the warming feedback described above is increasingly referred to as a ‘carbon bomb’. This analogy may be unnecessarily alarming, because as the climate warms increased tree growth will sequester a proportion of the carbon. Nevertheless, the potential climate effects are very serious, and this is why there is interest in the feasibility of restoring open herbivore-grassland steppes, with reduced albedo creating colder winter surface areas and helping to refreeze the permafrost.

In 2018, a team from Oxford led by Marc Macias-Fauria, a leading expert on Arctic ecology, teamed up with Nikita Zimov to publish a ‘first cut’ exploration of the feasibility of rewilding the Arctic at a scale that would have global climate impact. Rewilding in this situation means recovering herbivores at densities that would create and maintain grass- and herb-dominated ecosystems; encourage snow trampling by large herbivores as they move and forage for food, compacting the snow layer and leading to deeper winter soil freezing; increase evapotranspiration of grasses, reducing soil moisture and hence waterlogging which increases greenhouse gas-emitting microbial activity; and increase nutrient cycling and productivity, favouring deeper-rooted grasses and herbs (compared to tundra shrubs) and so increasing soil carbon storage. Modelling the amount of carbon emissions that could be avoided if steppe-like grasslands are restored is vital in order to assess whether Arctic rewilding makes policy sense, and to develop a business case to do so based on new policies that price carbon emissions (value per tonne) and that are creating market and other mechanisms to pay for net reductions in emissions.

The team presented some rough calculations which suggest that the feasibility of Arctic rewilding merits further investigation, and that between three and five large-scale rewilding experiments are needed, each involving 1,000 large herbivores, which would cost in the region of £25 million each over ten years. These experiments would investigate another crucial question: how to generate enough animals to conduct these experiments and enable future scaling if they produced compelling findings. Large numbers of bison and horses would be required to begin the experiments, but sources of these are few and the logistical challenges of transporting them to Arctic research sites and then acclimatising them to local conditions are huge. For example, should the Pleistocene Park become one of these experiments, it would require cold-adapted Yakutian horses, transporting them 800–1,000km by truck and barge. For bison, the nearest sizeable sources are ranches in North America, which would mean air-transporting them to the Russian port of Magadan. This is feasible: Nikita Zimov has already brought small numbers of bison via this route, but new infrastructure would be needed to transport large numbers of them to Siberia.

Added to this, it would be necessary to generate the political, scientific and cultural will to attempt rewilding in the Arctic at a significant scale. Large-scale megafaunal engineering is radical in almost every dimension. It would mean high-level political buy-in and new agreements that reward Russia and other Arctic countries for providing what would be a global public good. Institutions that govern the movements of livestock would need to create supportive policy to enable animals to be moved swiftly and efficiently across vast distances with little fodder on the way. In addition, the idea of transforming Siberia with livestock could prompt comparisons with discredited Stalinist policies to extend agriculture to Siberia. In short, attempting to restore ecosystem processes at scales that effect the Earth system is probably beyond the scope of a single rewilding initiative. Realistically, such effects can only accrue over the long term from multiple rewildings that recover ecosystem processes at both local and landscape scales.

Rewilding ecosystem processes

Some readers may be surprised by the emphasis we have given to herbivores and grazing rather than charismatic predators such as wolves, lynx and jaguars. This is because rewilding is fundamentally about the restoration of ecosystem processes – and it is the new understanding of ecological processes emerging from the interplay between herbivore grazing and vegetation structure and natural disturbance that represents the core contribution of rewilding science to the broader disciplines of ecological restoration and conservation science. This is not to say that predators are absent from the growing canon of rewilding science. In the previous chapter we noted the important role of predators in creating trophic cascades and ‘landscapes of fear’ and earlier in this chapter we saw the importance of animal digestion in accelerating nutrient cycling and transport. Scavenging is another important process influencing food webs and ecological communities and reducing the prevalence of disease in ecosystems: and the prey of large carnivores is a key factor supporting scavenging and decomposition – and through this the movement of energy across trophic levels.

Scavenging was, until relatively recently, quite widespread. Traditional herding and local abattoirs maintained large carcasses, or bits thereof, in the landscape, which supported scavengers such as vultures, blowflies and beetles and the many other animals that happily include carrion in their diet. Sadly, in the last 40 years scavenger populations have crashed across Europe, Asia and Africa. In Europe, biohazard regulations requiring the disposal of carcasses, the decline of traditional herding, and use of poisoned baits to kill predators (which attract scavengers) have mostly been to blame, but in Asia and Africa the cause is the widespread use of the veterinary drug diclofenac (banned since 2006) that caused vulture populations to collapse – by 95 per cent in India.

Modern-day perceptions of scavenger processes are mostly negative. The possibility of encountering a maggot-ridden horse carcass would be considered distasteful, and maybe even distressing, to most people. However, large herbivore carcasses are mini-ecosystems that supply large amounts of energy, water and materials. The carcass from a wolf kill provides a vital supply of carrion for smaller predators and birds big and small. A spring carcass offers fur for nesting material as well as a refuge and food sources for hundreds of species of beetle and fly. Large herbivore carcasses are key to the cycle of life and large predators are therefore vital to assuring a constant and scattered supply.

Rewilding science and practice is about restoring the full range of ecosystem interactions and dynamics, but advances in ecological science have firmly positioned herbivores at the core of processes that produce vibrant ecosystems across all scales from the local to the planetary.

* An emergent property is an attribute, quality or characteristic that a system has, but which the individual elements or components do not have.

† Ions are atoms in molecules that have gained or lost an electron, giving them a positive or negative charge.

‡ eDNA (environmental DNA) is DNA collected from the soil, water or even air, rather than from the organism itself. DNA deposited into the environment by organisms via their faeces, mucus, hair and carcasses accumulates over time, and although it degrades, modern DNA analysis can match fragments of DNA to reference collections.

7

REWILDING POLITICS AND ETHICS

Rewilding embodies advances in interdisciplinary conservation science: this is one reason why it is a hot science topic and why it is rapidly being included in the curricula of university ecology and conservation courses. Interdisciplinarity is something of a buzzword in the applied sciences, a response to the recognition that in order to bring about change in our ever more complex, global and technological world we need to draw on insights and evidence from multiple disciplines. True interdisciplinarity, where the various contributions are blended into a coherent whole, is rare and elusive. Rewilding is not there yet, but it is at the forefront of this endeavour and this is what makes it exciting and potentially transformational.

The conservation of nature has always been political. This is because it promotes a mix of values, morals and norms on how we should govern the relationship between the human and non-human worlds. It goes without saying that the practice of protecting and restoring nature involves trade-offs, with winners and losers. This generates debate as different groups advocate their particular needs and interests. For example, proposals to reintroduce wolves in Yellowstone and, more recently, in Scotland, provoke passionate debates between those who favour wilder natures and those, such as farmers, who see wolves as a threat to livestock and even their children! The media likes to report and polarise these differences because creating controversies attracts readers and viewers.

Some advocates also frame rewilding as an overtly political practice. Notable in this regard is the UK environmentalist George Monbiot, whose 2013 book Feral: Searching for Enchantment on the Frontiers of Rewilding propelled rewilding from obscurity into the mainstream of public discourse in the UK. However, Monbiot is a political activist and in Feral he aligned rewilding with an impassioned critique of the ills of modernity and the environmental degradation it has caused. He likened sheep to woolly maggots devouring the upland landscapes and ecosystems of Wales; for him this was an example of where the system had gone wrong and how rewilding approaches could create a better order. Unfortunately, this was received by many Welsh hill farmers as a direct attack on their culture, language and way of life by a middle-class English outsider. As a result, the term rewilding has become toxic in parts of Wales and in 2019 Rewilding Britain (an organisation Monbiot formed) felt the need to withdraw from a ‘Summit to Sea’ rewilding project they had initiated in Wales.

Understanding these dynamics and how to effect social and political change is the role of the humanities and social sciences. The disciplines of law, politics, history, philosophy, ethics, economics and psychology all have specialisms dealing with the environment – and all are contributing to the new science and practice of rewilding. Geographers are particularly active in the development of an interdisciplinary rewilding science because a major purpose of their discipline is to understand the complex interactions between Earth systems, nature and society.

The scientific method of the humanities and social sciences differs from that of the natural sciences, which we have so far discussed. Crucially, they do not believe that in the human world there are realities that can be known, quantified and modelled in the same way that we might know the components, interactions and properties of an ecosystem. Perhaps what sets us humans apart from other life on Earth is the fact that we exist in a triple reality: the reality of the physical world, the reality of our feelings, and the reality of our collective stories and imaginations. This latter reality – what may be referred to as cognition or culture – emerged in our species approximately 70,000 years ago.

Social scientists are acutely aware of the dangers of applying natural science theories, built from quantitative understandings of physical realities, to the world of human sociality. The theory of evolution is a case in point. The evidence that species could emerge from natural interactions and were not created by a divine power challenged dominant narratives that ordered individual and collective belief systems in 19th-century western society. There is no doubt that the theory transformed the western mind, but ‘Social Darwinism’ – the idea that people and groups are subject to the same laws of natural selection as plants and animals – gave rise to eugenics and a rationale that human inequality was natural and even necessary for the advancement of our species. Nazi Germany’s race policy that led to the Holocaust was a horrific example of allowing theories of physical realities to shape political ideology without powerful intellectual checks.

For such reasons, social scientists understand theory not as sets of hypotheses developed, tested and refined with objective facts, but as ‘conceptual resources’ – structured ways of thinking that generate new insights on different aspects of society and new forms of evidence to support collective decision-making. These conceptual resources draw heavily on qualitative evidence such as observations, interviews, and text analysis to provide deeper and more nuanced information than numbers alone can do. Many social scientists studying environmental issues are motivated by a desire to address the roots of inequality and injustice. Their approach is great for answering questions such as ‘What is nature?’; ‘Why is rewilding so compelling for some and so objectionable to others?’; and ‘How can we generate the support and buy-in to scale up rewilding?’

Conservation narratives

Rewilding is a fresh approach to nature conservation which, as we hope we have explained, expresses new ecological understandings and theory. However, within the professional world of conservation it is only just beginning to find traction. Many technical experts in conservation organisations have never heard of it, and few will have had either the time, inclination or access to academic articles to engage with the science. To many conservation officials, rewilding appears ‘faddy’, concerned with controversial species such as wolves, out of line with established ways of doing things, and in tension with conservation law, making it risky and unproven and politically sensitive. But why should this be the case? Why aren’t the big conservation NGOs and government agencies rushing to give it a try in at least some of the many natural areas they own or manage? Three concepts from cultural and social theory – narratives, frames and institutions – offer a powerful lens through which to address this question, and also to ask why rewilding so readily becomes political when it is put into practice.

Generally speaking, the term ‘narrative’ refers to the way a story is told, but in the policy sciences, it is used in a more structured sense to refer to building blocks or components that are combined to create ‘architectures’ – to tell stories about the state of the world, the consequences of this, and what should be done. Environmentalism took off in the 1970s because thought-leaders constructed a powerful narrative architecture that changed attitudes, mobilised action and structured laws, thinking and practices of government and non-government conservation agencies. In rewilding, we are seeing the emergence of a new narrative architecture and this unsettles and questions institutionalised ways of doing conservation. Unsurprisingly, institutions resist change, viewing it as risky, time-consuming and difficult.

The basic architecture of the 20th-century environmental narrative was outlined in a series of popular books published between 1948 and 1962. The first two of these, Fairfield Osborn’s Our Plundered Planet and William Vogt’s The Road to Survival (both published in 1948) established three key narrative components: 1) nature, soils and the environment are in decline; 2) human fecundity and poor stewardship are to blame; and 3) without action, humanity faces catastrophe. In her seminal 1962 book Silent Spring Rachel Carson added a sense of impending alarm to these three narrative components. Deploying the powerful metaphor of a spring without rebirth, she told of the awful effects that pesticides were having on the environment, of a chemical industry spreading disinformation to chase profit, and the catastrophic consequences for nature and humanity.

In East Coast America and western Europe, the physical manifestations of Carson’s compelling narrative were plain to see – polluted rivers, smog, trash, and the collapse of predatory bird populations. It was taken up by a young, well-educated, middle-class generation with the activist confidence of 1960s counterculture. They populated the narrative with villains – polluting industries, agrochemical companies, Russian whaling fleets, complacent government agencies and so forth – who could become the target of campaigns. This new environmental consciousness found mass expression on 22 April 1970, when millions took to the streets and parks to call for a healthy environment.

This narrative structure transformed politics and policy. Governments negotiated environmental treaties, passed laws and established ministries and agencies to regulate the perpetrators of harm and protect the best natural areas from humanity’s worst excesses. Consciously or otherwise, scientists responded with research programmes to build the evidence base for this narrative, and activist organisations formed to keep up the pressure on governments and corporations to save humanity from chaos. The climate crisis is re-energising this environmental narrative, and across the world schoolchildren are taking it up and protesting along with older generations of environmentally conscious citizens. Unfortunately, governments of today seem less willing to act with the same urgency and conviction as in the 1980s.

Rewilding as a new environmental narrative

Stories of rewilding appear to be adopting a quite different narrative structure. As we heard in Chapter 4, rewilders are telling stories that are fresh, empowering and hopeful. They talk about restoring trophic interactions, the return of megafauna and recovery of river dynamics, and the power of demonstration projects to reset expectations of the possible in conservation. In 2018, one of the present authors (PJ) wrote an article reflecting on this new narrative which he labelled ‘Recoverable Earth’, contrasting it with the established ‘Finite Earth’ narrative. He pointed out that stories of rewilding lack the blame and the appeal to higher authority of the 20th-century environmental narrative, instead focusing on new ways of thinking and grounded action, intertwined with ideas of nature as a creative force and visions of a better future for all life. The components of the Recoverable Earth narrative are very similar to accounts of mental health recovery, characterised by taking stock and putting aside blame, awakenings, decisions to act, and reassessment, leading to the recovery of ‘wellness’ (Figure 4).

The emerging rewilding narrative presents the degraded state of nature as the outcome of complex interactions between nature, culture, politics and economy over the long term. Given this, there is little value in feeling guilt and attributing blame: we are where we are and there is no way back, yet pragmatically, we can take stock, reassess and start doing things ourselves to shape a better future. Rewilding stories, like accounts of recovery from mental health, commonly talk of ‘awakenings’ that prompt a desire to do something, which leads to a reassessment and more action through which a recovery emerges.

Fig. 4: Comparison of the structure of the established environmental narrative and the emerging rewilding narrative.

Isabella Tree, author of the bestselling book Wilding (2018), adopts this narrative structure in her account of how she and her husband transformed their ancestral Knepp Castle estate in southern England from farmla nd to Britain’s most famous rewilding project. She starts by describing the ‘cycle of drudgery’ they found themselves living as they tried to turn a profit from ever more intensive farming practice. Then she tells of how a project to restore parkland opened their eyes to fresh possibilities and this led them to engage with Frans Vera’s new ideas on grazing and wood-pasture landscapes. Inspired, they decided to embark on an experiment to develop a rewilding model of estate management involving free-roaming livestock, the removal of fences and relaxation of land management. The rebounding of wildlife and rare species and the recovery of soils has been remarkable. Tree’s story is one of hope and empowerment where a willingness to think differently and embark on an uncertain journey towards a better future has led to the recovery of nature, their quality of life, and the estate’s finances.

Narrative interplays

There is a lot at stake in maintaining the established environmental narrative and the institutions it has founded. A huge body of science, rules and regulations, bureaucratic procedures, business models and careers and reputations are founded on it. Furthermore, the environmental crisis is real, and environmental lobbyists rightly worry that a new narrative that talks about the millennia-long impacts of human activities on ecosystems and climate, and argues that through rewilding ecosystems can recover, could be seized upon by politicians and corporate interests who are reluctant to act with the urgency and commitment needed to address the linked climate and ecological crisis.

The policy science literature shows that narratives based around anxiety are effective at getting governments and corporations to act because both fear the consequences of political, social and economic instability. However, the psychology literature and indeed common sense suggest that for people faced with the worries of everyday life, the constant retelling of ‘doom and gloom’ stories concerning the future can become overwhelming and generate a sense of social and personal anger and malaise. Some suggest that rewilding signifies a desire for people to regain control and create, shape and live stories of a better future.

How the established environmental narrative and the new rewilding narrative will interact is unclear. The ideal would be an environmental movement that adopted both, with the knowledge and skills to use them to mobilise different groups in society in different contexts. What is clear is that this interplay is already happening. Many rewilding practitioners are gifted communicators and are putting story-telling at the heart of their approach. Peter Cairns, founder of Scotland: the Big Picture (StBP) intuitively knows that it is vital to engage people in a journey of fresh thinking. Through books and lecture tours illustrated with stunning photography, the StBP team introduces nature as a wholeness woven from infinite complexity; without assigning blame, StBP tells how through ‘just getting on with life’, we have unravelled the whole. The StBP story explains that trying to save nature piece by piece isn’t enough, and that at its most basic level, rewilding is about joining up and expanding bits of nature rather than fragmenting them further. Central to StBP’s narrative is the need to think big, for Scottish people to unlock their imaginations to envisage a future that will be better for all life – people and nature – and to act boldly. Crucially, StBP’s narrative doesn’t tell people what needs to be done; rather it invites them to engage with new ways of thinking and collectively formulate new ways of doing conservation.

This way of presenting rewilding aligns with what is known as the dialogue model of science communication, founded on the belief that discussion based on different forms of evidence creates understanding, leading to action. It contrasts with the deficit model of science communication that characterises the establishment environmental narrative, which assumes that if people knew the facts they would act wisely. Each model has different impacts in different settings and with different people, but rewilding’s narrative offers an alternative to the relentless communication of facts that foretell an ecological and climate emergency and the failure of others to do the right thing.

Why rewilding antagonises farmers and ranchers

The concept of narrative is valuable in understanding why rewilding unsettles established institutions, and it is not hard to see how the blame element of the classic environmental narrative puts people on the defensive. However, another social theory, called ‘frame analytics’ or ‘concepts of the frame’, offers a way to analyse controversies and to design rewilding initiatives in ways that enrol, rather than alienate people.

The influential American social psychologist Erving Goffman introduced ‘framing’ in 1974 to signify processes of sense-making and collective action. He described frames as ‘schemata of interpretation’ and proposed that people make sense of, and act within, a complex world by subconsciously gathering together metaphors, facts, narratives, images, memories, feelings and so forth (called ‘ideational elements’ in the jargon) into ‘frames’. The term frame is intentionally used to suggest both a framework and a picture frame. Frames are individual and flow into each other in our heads, but we all constantly make use of a cultural stock of frames that arises from ‘sedimented’ histories of collective engagements with each other, the world around us and other peoples and cultures. In short, our mental framing processes are central to our sense of identity.

For most people, rewilding is a new and unfamiliar concept and, naturally, they link it to their existing frames. This became all too evident to Curt Freese and Sean Gerrity when they launched an initiative to rewild the northern plains of Montana in the USA. When the American explorer Meriwether Lewis scouted the Great Plains in 1803 he described how he could ‘scarcely cast his eyes’ over the short grass prairies ‘without perceiving deer, elk, buffalo or antelopes’ and how ‘wolves appear to increase in the same proportion’. Subsequently, 270,000 homesteaders flooded into the prairies: the region’s earlier peoples were shunted into reservations and the prairie grasslands were tilled, fenced and divided. Within a century, the vast herds were gone, but although this wildlife wonder was destroyed, the grasslands – the foundation of the ecosystem – held on. This was because the harsh winters and scant rainfall drove out most of the homesteaders and those that remained transitioned to low-intensity ranching, the only viable economic use of lands where the climate is too extreme for agriculture and for woody vegetation to grow.

When Freese, a WWF biologist, looked at the northern plains he saw the 400 hectare (ha) Charles M. Russell National Wildlife Refuge and the 150 ha Upper Missouri River Breaks National Monument located among vast areas of private ranch land interspersed with government-owned land parcels. He discussed this with Sean Gerrity, a Silicon Valley consultant, who saw the private lands as an opportunity rather than a constraint. The two founded the American Prairie Reserve (APR), a non-profit organisation with the audacious plan to buy ranches as they came on the market and restore the herds parcel by parcel.

Not surprisingly, their vision clashed with the ‘cowboy’ frontier frames of independence, resilience, neighbourly solidarity and ranching. The APR was framed locally as rich techie outsiders, wanting to replace the cowboys with buffalo and insult their culture. Resistance to the APR’s rewilding vision was swift and firm: ‘Save the Cowboy: Stop American Prairie Reserve’ signs sprang up and 133 landowners organised to prohibit bison on their collective properties. The Montana legislature passed a resolution asking the government to deny APR permission to graze buffalo on state land. APR’s vision also caused conflict within the rancher community, dividing those who saw it as a threat to their way of life and those who saw the possibility of new enterprise opportunities. George Horse Capture Jr, leader of Fort Belknap Reservation’s tourism branch, saw the proposal to create America’s largest reserve as an opportunity for Native Americans and ranchers to join together to shape a future that would recall both their heritages and create a shared economy. With more attention to framing at the outset, APR might have built a unique coalition to take forward their rewilding vision. As it is, the project is going ahead and is creating a huge rewilding area, but with some continued opposition.

The Conservation Land Trust (CLT) faced a similar situation when, in 1997, they started buying large areas of land adjoining the Iberá provincial park in Argentina. Their rewilding vision was not dissimilar to APR’s, namely, to reverse historic processes of defaunation through bringing back lost species, in this case tapirs, giant anteaters, peccaries and jaguars. From a technical perspective, their rewilding strategy had an elegant logic: the Iberá provincial park authority was required to protect the ecosystem that was present at the time the park was designated. However, by that time many key functional species were missing. They reasoned that if a private organisation rewilded adjoining lands and then gifted these to the government, this would create a need to designate a larger park based on the ‘upgraded’ rewilding baseline. From the perspective of local ranchers, the idea of buying up land for no productive purpose made absolutely no sense. To fill this void, they framed the purpose of CLT as a CIA plot to buy land under the guise of conservation as a means to exert political control in Argentina. So compelling was this frame that the CLT nearly abandoned the project.

This crisis caused the CLT team, led by Ignacio Jiménez-Pérez and Talía Zamboni, to reassess their approach. In meetings with politicians, bureaucrats and businesspeople they started using the term ‘nature production’ to describe the rewilding initiative and framed their species-reintroduction efforts in terms of creating a new wildlife ‘product’ to attract tourists. In this way CLT bridged the rewilding frame with important frames of economic development and business enterprise. Secondly, CLT actively blended images and traditions of the local cowboy culture into their vision and communications. This was a two-way process of what it technically termed ‘frame amplification’, where the recovery of wildlife amplified and extended local people’s sense of heritage and pride, and the culture of the Corrientes province amplified CLT’s framing of what rewilding could be. The outcome was frame ‘alignment’, where rewilding became a shared and rewarding journey. In 2018, the Iberá national park was created, combining the 525,000 ha provincial park and the circa 140,000 ha donated by CLT to create Argentina’s largest natural area. In the same year the first jaguar cubs in 70 years were born in Corrientes.

The challenge of bridging different moral world views

Frames and narratives, together with experiences and representations, shape our worldview. Within conservation there has been a long-standing tension between ‘protectionist’ and ‘sustainable use’ worldviews. These reflect the distinction between two moral codes, namely moral absolutism which believes that judgements of right and wrong should be assessed against a series of pre-existing rules, rights and duties; and moral pragmatism which argues that the morality of an action should be based on its outcomes and the extent which it serves the greater good. In his influential book Moral Tribes, Joshua Greene draws on the analogy of ‘automatic’ versus ‘manual’ settings to explore the distinction between these two moral codes. He points out that cameras have both settings because auto-settings based on programmed rules produce a good photo outcome in most situations, but they lack the flexibility to produce a good outcome in more complex or challenging settings. One of the great challenges for rewilding is how to deal with different moral worldviews concerning how humans should relate to animals.

The campaign to ban trophy-hunting and the moral and ethical questions raised by de-domestication and de-extinction illustrate the moral landscape that rewilding must navigate. For many animal lovers, the idea of shooting lions, elephants, wolves, bighorn sheep and other iconic wildlife for sport appears cruel, uncivilised, and a risk to their survival. Nineteenth-century campaigns to end cruelty to work-horses and other domestic animals embedded values of animal compassion and welfare in western culture and aligned with the conservation values of avoiding extinction. Unsurprisingly, images of rich Americans posing proudly over magnificent, but dead, wild animals prompt feelings of outrage among the western public and generate support for organisations who seek to outlaw such practices.

These campaigns are particularly focused on southern African countries which developed a ‘wildlife economy’ approach to nature conservation in the wake of apartheid. The region’s elephants, rhinos, buffalo and other megafauna were virtually wiped out during the 1980s by militia and regular armies, for food, sport and profit. Nelson Mandela, South Africa’s first post-apartheid president, recognised that wildlife was central to his country’s natural identity, but knew that his government could not prioritise its protection and recovery due to other pressing issues. He appealed to the private sector to take the lead. To support this, the South African government passed a law that made wildlife the property of the owner of the land where it was found. This turned wildlife into a private asset which landowners could commercialise. Many farmers switched to game ranching and investors bought up failing farms to create private game ranches.

By 2010 there were over 10,000 private wildlife ranches in South Africa. Private landowners have rewilded landscapes, supported an abundance of wildlife, and brought a level of prosperity and stability to rural areas. However, their business model is based on revenue from a mix of hunting, wildlife safaris, wild meat (e.g. biltong) and game breeding. Hunting revenues are by far the most important of these, but are under threat from social media campaigns to stigmatise hunting tourism and restrict the transport and import of hunting trophies. Achieving rewilding in a southern African context requires a ‘manual’ setting approach where moral questions concerning the rights and wrongs of big-game hunting are tempered to allow ecosystems to recover.

However, the Oostvaardersplassen (OVP) in the Netherlands, which we described in some detail in Chapter 4, is an example of the reverse: where rewilding’s ecological pragmatism needs to be tempered by intuitive judgements of right and wrong. The OVP involves the de-domestication of horse and cattle breeds to restore natural grazing dynamics and allow nature to ‘find its own way’. However, the hard winter of 2017/18 caused thousands of horses in the reserve to starve. For the reserve managers, this was part of a natural process: numbers had built up during a run of mild winters and climate was a natural regulator of numbers. But for many Dutch citizens, allowing horses to starve and then culling the 3,000 that would have succumbed naturally was an outrage with no place in a modern, caring society. Animal welfare activists teamed up with farmers to throw bales of hay over the fences and launched a forthright campaign that forced the authorities to rethink. They decided that herd numbers should be managed within the carrying capacity of the reserve, thereby curtailing the experimental principle of letting nature go its own way. The lesson from the OVP is that rewilding’s pragmatic morality needs to understand and respect cultural values and morality based on more black-and-white rules.

De-domestication and de-extinction

The concept of extinction has provided societies around the world with a clear and widely accepted moral code: it is morally wrong to knowingly cause the extinction of another species. The slogan ‘extinction is forever’ is a long-standing clarion call of the conservation movement. Extinction originally referred to the demise of the last individual of a species; when Martha the passenger pigeon died in 1914, the species was formally declared extinct. The rewilding ethos is redefining the boundaries of extinction from a living animal to living DNA, and this requires a readjustment of moral codes.

The aurochs, Europe’s wild cattle, was formally declared to have gone extinct in 1621, but Ronald Goderie, Founder of the Tauros Foundation (TF), realised that its DNA survived in Europe’s 88 million domestic cattle and especially in more primitive breeds. Sets of genetic code (known as a haplotype) enable the history of breeding to be traced backwards, and Goderie reasoned that the science of animal breeding, which historically has favoured animals producing more meat or milk, could be reversed to create a breed that resembled the extinct aurochs and could fulfil a similar ecological role in the wild. He started crossbreeding seven primitive breeds of cows to create the Tauros – a breed with the larger horns (to fend off wolves), longer legs (to cover more ground) and smaller udders (to avoid snagging) that characterised the aurochs.

The Tauros project is now partnering with animal breeding scientists to more systematically match the Tauros genotype with that of the extinct aurochs. This is enabled by advances in ancient DNA extraction and analysis (referred to in Chapter 3). In 2015, the first whole genome sequence was published from DNA extracted from a 650-year-old British aurochs bone. Subsequently, three additional sequences have been published. DNA fragments over time, and museum specimens are easily contaminated with DNA from their curators, other specimens and pest organisms that get into the collections. However, advances in computation mean that it is now possible to match even very short strings of DNA and construct whole genomes from degraded ancient DNA. Phylogenomic analysis, as it is known, seeks to recreate evolutionary lineages: for researchers partnering with the Tauros Foundation it provides an aurochs gene sequence that can be compared with the sequence of existing breeds to accelerate a programme of cross-breeding to produce animals with genomes that are closer and closer to that of the aurochs.

At the time of writing, there are approximately 700 Tauros in ten European areas. They are magnificent animals that certainly look and act like our imaginings of their wild ancestors. The TF chose to call the new breed Tauros rather than aurochs to make the point that it is not possible to recreate a historic species – it would have changed in the intervening 500 years since its ecological extinction in any case. In addition, creating distance between the wild aurochs and the new Tauros breeds enables blurring of the boundaries between wild and domestic. On the one hand, people will consider the Tauros wild on account of its looks and behaviour and hence not subject to the same welfare morality as domestic cattle species. On the other hand, treating it a special breed of cattle means that variations can be bred suited to different conditions, such as a longer-legged wetland variety and a more docile variety for semi-urban situations. It also positions the Tauros as a new type of livestock that should be eligible for government subsidies.

The Tauros shows that if living DNA still exists in domestic descendants, an extinct species can ‘rise from the dead’. This, together with public interest in gene-editing and cloning, has given rise to some extreme rewilding visions, notably the one to resurrect the woolly mammoth. A team at Harvard, led by George Church, is working to produce a hybrid elephant-mammoth embryo and implant this in an Asian elephant in the hope that she will give birth to an elephant with mammoth-like characteristics – a creation sometimes referred to as a ‘mammophant’. In her bestselling book How to Clone a Mammoth, Beth Shapiro comprehensively explains the science and examines the feasibility and ethics of ‘de-extinction’. She points out that it is one thing to create an individual that exhibits characteristics of an extinct species and quite another to recreate herd and social behaviours and the learnt knowledge of how to live in nature. Furthermore, de-extinction would raise huge ethical and moral questions. For example, is it right to create new creatures, especially sentient ones such as a mammophant? What responsibilities would we have for them? Could we ‘re-extinct’ them if funding ran out? In short, de-domestication is possible and underway, but de-extinction is another ball game altogether.

Rewilding needs slow thinking

This chapter has shown that rewilding challenges our fundamental understanding of nature and the ways we make sense of ourselves and others. Any form of progressive change requires adjustments in attitudes, cultural frames and institutional practices. In 2002, Daniel Kahneman won the Nobel Prize for his work with Amos Tversky on how we make decisions and assess losses and gains. In his hugely influential 2011 bestseller Thinking, Fast and Slow, Kahneman describes how we humans have a dual-processor brain. The first process – System 1 – is fast, intuitive and always on. Among other things it is impressionistic, stereotypic and emotional. System 2 is deliberate, reflective and requires attention. Joshua Greene’s work on morality mentioned earlier is influenced by Kahneman’s ideas. The point is that rewilding requires ‘slow thinking’ but the world of politics and media more often than not plays to System 1 thinking. This is one reason why rewilding, as an unsettling new approach to nature conservation, so easily generates concern and controversy.

In October 2019, leading rewilding practitioners from across Europe met in Cuenca, Spain to share learning and formulate a set of principles that they believe characterise European rewilding and offer a guide to success. Their nine principles* emphasise the importance of starting slowly with inspiring and empowering visions that encourage engagement and practical action. They emphasise the importance of acting in context, of paying attention to ecological and cultural history and local political and economic realities, and seeking coalitions to shape rewilding futures. In Europe at least, rewilding is becoming ‘slow conservation’ in which people from different backgrounds are invited to participate in journeys of reflection and reassessment that will support creative thinking and rewilding visions with the potential to revitalise landscapes for nature and people.

* See https://rewildingeurope.com/callforawildereurope/

8

SCALING UP REWILDING

The last chapter explored the reasons why rewilding unsettles and generates controversy among different groups in society. In this chapter we will focus on the applied practice of rewilding: the approaches that rewilders are developing in an effort to scale up rewilding from a niche activity to one that can recover ecological processes across landscapes and whole regions.

Rewilding at scale needs five crucial things: land, ‘buy-in’, supportive policy, a supply of animals, and money. All of these are in short supply, and the extent to which each is available, or can be generated, shapes how rewilding is approached and its chances of success.

For example, the Iberá rewilding programme in Argentina was supported by the wealthy philanthropists Douglas and Kristine Tompkins (founders of the Patagonia clothing brand) who had the money to buy land and could source captive giant anteaters, collared peccaries, green-winged macaws and jaguars for release. However, as described in the last chapter, they initially lacked the support of local communities and the provincial wildlife authorities who refused permits to translocate animals from other areas. They avoided failure by presenting rewilding as ‘nature production’ – the recovery of wildlife assets that would revitalise aspects of the local cowboy culture and generate new tourism-related jobs and investment. This created the local buy-in and policy support necessary for success.

In southern England, Charles Burrell and Isabella Tree, owners of the 1,420 ha Knepp estate, had the land and money to embark upon their Knepp Wildland project and have been adept at generating buy-in from ecologists, the media and a broad swathe of public opinion. However, to create a viable business they have to work within the constraints of UK agricultural policy. This means that, for example, they cannot allow cattle to die natural deaths or leave carcasses to encourage the recovery of scavenger and decomposer ecosystems. Furthermore, their estate is bounded by main roads, and even though there is interest from neighbouring estates in replicating their model, connecting them up would require building ecoducts (natural bridges across roads) at huge expense.

A team from the German Centre for Integrative Biodiversity Research (iDiv) felt it was important to recognise these constraints and in 2018 published a scale of rewilding progress. This approach recognises that moving from a very low level to a higher level, e.g. from 2 to 5 on the scale, is just as good as moving from scale 8 to a fully rewilded scale 10. Indeed, in some contexts it may represent an even more significant achievement. Their scale gave meaning to an emerging principle of the rewilding movement, namely that the goal should be to move up a scale of rewilding within the constraints of what is possible. This principle presents rewilding professionals with a clear challenge: how to reduce or remove constraints such that the necessary land, buy-in, support, animals and finance become available and rewilding can take off.

Systems thinking and rewilding models

The science of rewilding prioritises relationships and processes and, perhaps unsurprisingly, many practitioners are systems thinkers who apply a holistic philosophy when designing mechanisms to create the conditions for rewilding. Systems thinking involves an openness to understanding the complex systems and forces that shape our world, and a willingness to pragmatically engage with these to assemble new systems. Such thinking is based on the logic of emergence – if the right system elements are in place, desirable outcomes will emerge and persist. However, the outcomes that emerge might not be quite what was planned or indeed desired: a willingness to embrace uncertainty and a degree of risk is central to systems approaches and to rewilding’s emerging action philosophy.

Present-day institutions of nature protection are founded on linear thinking based on causality (cause and effect relationships): an action and reaction, a problem and a solution. Most of us have been taught to see things linearly and as a result we tend to simplify the messiness of the world to fit this model. Such a framework has been particularly influential in shaping the philosophy of both governments and major conservation organisations: human activities exert pressures on nature, causing a decline in its quality and abundance. Removing and limiting these pressures will enable nature to recover. This logic is expressed in laws protecting species from persecution and requiring states to designate conservation areas that are spared from damaging pressures.

In Europe this approach, and a strong focus on protection, has achieved some notable successes. It has preserved vulnerable sites and led to a comeback of many species of wildlife. For instance, a 2013 study showed that populations of brown bear, Eurasian lynx, grey wolf, wolverine and golden jackal are all increasing across Europe as a result of legislation and changes in public opinion. Indeed, there are now more wolves and brown bears in Europe than there are in North America, and many live outside conservation areas in highly developed landscapes in Germany and elsewhere. However, the overall level of nature in Europe is still low and, as discussed in Chapter 3, populations of common birds and insects are in rapid decline. The protection approach with its simple linear model of causality is a crucial part of the repertoire of conservation action, but it lacks the scope and sophistication to recover natural processes at scale.

The rest of this chapter will show how those employing systems thinking are seeking to turn constraints into opportunities and shape a new conservation action philosophy. This is most evident in Europe, and the following section draws heavily on the pioneering work of a group of Dutch rewilders. A catalytic figure in this network is Wouter Helmer who, as one of the founders of ARK Nature in 1989, pioneered rewilding approaches and later founded Rewilding Europe (2011) and the European Rewilding Network together with Frans Schepers, Staffan Widstrand and Neil Birnie.

Investing in rewilding

Rewilding to scale needs to attract finance from companies, public sector agencies and financial institutions, who will invest because rewilding generates returns that positively affect their bottom line. Wouter Helmer recognised this 30 years ago when ARK Nature initiated a small rewilding project in the highly engineered setting of the River Waal (a branch of the Rhine) near the Dutch city of Nijmegen. He was inspired by ‘Plan Stork’ (of which Frans Vera was one of the authors), a progressive vision to remove the dykes (banks) constructed to control summer flooding and restore natural river braiding and grazing with free-roaming horses and cattle. Alongside rewilding, the plan offered policy-makers a natural solution to managing extreme flood events, which were on the rise due to climate change. Crucially, Helmer and his colleagues realised that brick companies and the aggregate industry might be willing partners in river restoration with the ability to mobilise the capital to bring about the transition.

All countries need a supply of clays and sands to build houses, roads and other infrastructure. Deposits of these materials naturally accumulate in the floodplains of slower-moving rivers, but traditional ways of mining and extraction are destroying these landscapes. Plans to extract more therefore provoke vigorous public opposition, which costs time and money. Performed in a more subtle way, however, superficial extraction of these renewable sediments creates a perfect starting point for ecological recovery. WWF Netherlands used its standing to help broker a deal between brick companies, the river management agency and ARK Nature. The Gelderse Poort scheme, as it came to be known, offered three things with significant commercial value for a brick company: a substantial and renewable source of easily accessible clays and sands, a social licence to operate, and an enhanced reputation. In return, the brick companies agreed to excavate and restore the old river channels and braids over a period of twenty years. As the dynamic floodplain recovered and wilded herds were re-established, ARK Nature reintroduced beaver and sturgeon, supported the return of otters, ran a school educational programme, started a wilderness café and encouraged people to visit and experience the new nature.

The outcomes for nature have been remarkable and unexpected: as the natural flows recovered, the river created sand dunes and a series of banks. The latter filtered water and created a complex of backwaters, each with less dissolved nutrients and therefore supporting aquatic communities that were previously known only from upland lakes. At the same time, the restoration of a floodplain extending over 3,000 ha meant that government had to spend less on flood defences while Nijmegen’s residents benefited from the wonderful new recreational opportunities on their doorstep. Local pride was enhanced when in 2018 Nijmegen was awarded the prestigious European Green Capital status.

The power of demonstration projects

By looking beyond traditional sources of conservation finance and seeing aggregate mining as an opportunity rather than a threat, Dutch rewilders achieved the quadruple challenge of land, buy-in, public support and money. Crucially, ARK Nature adopted a systems approach that presented rewilding as a pioneering new philosophy of river management with the potential to solve major flood-risk challenges and, at the same time, enhance the quality of life for citizens. By starting small and with a compelling vision (wild horses galloping across the Dutch delta) and a radical new approach (a partnership with industry), the Gelderse Poort attracted interest and engaged others in the slow thinking described in the last chapter, and this had ripple effects across different sectors of society.

WWF Netherlands launched a ‘Living Rivers’ campaign with the strapline ‘Building with bricks = building on nature’, bold new river rewilding projects such as the Border Meuse (on the Netherlands–Belgian border) were initiated, and over a period of twenty years, the institutions of Dutch river management transitioned from an engineering model of dykes and dams to natural river management on tens of thousands of hectares. River rewilding is now normal in the Netherlands and is being adopted in France and Germany, and also along the Danube and in China.

Nature-based solutions

Presenting rewilding as a potential solution to contemporary social and environmental problems is an effective way to build coalitions between conservationists, policy-makers and forward-looking professionals in different sectors such as civil engineering, health and tourism. Indeed, rewilding science and its visions have contributed to a new policy concept labelled ‘nature-based solutions’. These are broadly defined as actions that work with and enhance nature so as to help people adapt to change and provide societal benefits.

In many regions of Europe, the combined effects of climate change and the drive for agricultural efficiency are creating major policy challenges but also opportunities to extend the scale and scope of rewilding. For example, regions of central Spain are depopulating as the combination of hotter, drier summers and marginal agricultural land makes farming unviable. As land is abandoned scrub grows, increasing the risk of damaging wildfires. In addition, as families leave the villages in search of work in the cities, the cost per person of providing public services in rural areas has increased. In 2019, a group of rewilders mobilised to found Rewilding Iberia and work with local stakeholders to develop a vision for a large area to the west of Madrid where the human population density has fallen to below that of rural Namibia.

The region covers a wild landscape of rocky gorges and outcrops interspersed with forest plantations, patches of agriculture, scenic villages and, significantly, the castle of Zafra, which was used as the Castle of Joy in the sixth season of Game of Thrones. This cultural asset has inspired the idea of a new ‘Three Kingdoms’ tourism destination – a natural theatre where herds of Tauros, kulan (European wild ass) and deer roam across the plains and among the castles, gorges and medieval villages, and where wolves, lynx, vultures and eagles hunt and scavenge. This rewilded setting would create opportunities for photo-safaris, adventure sports and cultural tourism to rival anything Africa has to offer, but within two hours of one of Europe’s major capitals. This kind of ability to analyse systems in decline and imagine new nature-based economies may be the key to scaling up rewilding. Offering new economic futures for lands that are becoming agriculturally marginal avoids the need for conservationists to purchase land, and creates the potential to attract government funds for regional development.

The climate emergency may also represent an opportunity for rewilding. Since the 2015 Paris climate agreement, countries around the world have started intensifying the action and investment needed for a transition towards a sustainable low-carbon future. Interest is growing in natural climate solutions and, as we saw in Chapters 3 and 6 with Arctic rewilding and the Pleistocene Park, rewilding offers a potential way forward. However, in order to develop rewilding into a climate solution, practitioners need to become savvy in the emerging field of carbon finance. In brief, governments are introducing a variety of regulatory frameworks to stimulate markets for carbon. For example, in 2005 the European Union set up a ‘cap and trade’ system where a regulatory cap is put on the net amount of emissions an industry is allowed to emit. The cap is reduced over time such that industries need to invest in low-carbon technology, buying credits if carbon emissions exceed their cap. If rewilding projects can demonstrate measurable reductions in carbon emissions and/or carbon capture, they can sell these as credits and generate an income stream for rewilding projects.

Peatland – bog and fen – biomes are attracting a lot of interest in the arena of carbon finance. This is because peatlands are made up of wet, spongy organic soils that become large emitters of carbon if they dry out. Rewetting degraded peatlands can significantly reduce carbon emissions and generate large numbers of carbon credits per unit of area. The possibility that rewilding could increase the value of carbon credits and hence the business case for investing in peatland restoration and rewilding is currently being explored. The logic is that rewilding will reduce management costs in the mid- to long term and will add a rewilding story for which PR-conscious companies seeking to reduce their carbon footprint will pay a premium. Peatland rewilding should generate valuable new knowledge on the links between ecological recovery and carbon finance which will be invaluable to the wider effort to scale up rewilding. This is because it provides rewilding practitioners with the know-how to include carbon sequestration and reduced emissions – a benefit and potential revenue stream – in the design of new rewilding initiatives.

The European Wildlife Bank

A key theme of this book has been the importance of grazer–vegetation interactions for generating ecological complexity. As we have seen, recovering large herbivore populations also creates opportunities for rewilding to become part of nature-based solutions to some of the big challenges of our age. However, outside southern Africa, wild mega-herbivores are either extinct or in very short supply, surviving in small, isolated populations, as rare domestic breeds or in zoos. In order to move from demonstration projects to a larger scale, rewilders need to address two practical constraints: how to create a pipeline of animals for release, and how to overcome what is known as ‘regulatory drag’ – the painfully slow, bureaucratic process of doing something new where large animals are involved.

European rewilders are innovating on both accounts and taking inspiration from aspects of the South African wildlife economy model discussed in the last chapter. Of course, the situation in Europe is quite different to that in Africa. Europe lost its wild mega-herbivores centuries ago and they have become culturally extinct. Europeans know cows and horses, not aurochs and tarpans, and think of bison as North American rather than European species. Nonetheless, these three mega-herbivores, along with the European wild ass, survive in domestic forms. To enable the expansion of natural grazing and the de-domestication of cattle and horses, the Rewilding Europe team designed an innovative ‘wildlife bank’ to grow the necessary numbers of Konik horses (a rare breed resembling the tarpan), European bison and Tauros. Like a conventional bank, the European Wildlife Bank (EWB) owns assets, but these are in the form of herds which it loans to members in the European Rewilding Network under a contract that requires them to pay back to the bank half of the herd after five years. Under good conditions, herds can grow by 20–25 per cent per year, so members can obtain founder herds with limited financial outlay. This model enables the bank to grow and reinvest its wildlife capital in other rewilding locations and for rewilding projects to obtain herbivores at low cost.

Importantly, the EWB creates an entity that can attract investment to introduce new breeds into the bank, build the professional expertise needed to breed and translocate these wilded animals, and engage with institutions that govern and regulate domestic livestock. In the last chapter we discussed some of the ethical issues associated with de-domestication. The EWB and its members are at the forefront of de-domestication. Among other things they are creating rewilding breeds that resemble their wild ancestors in looks, behaviour and ecological role, developing management models that support the cultural transition from domestic to wild and, as we will see below, are beginning to work with policy-makers to create a more supportive regulatory environment. However, the supply of animals is still relatively low and if substantial funds were to become available to restore large-herbivore guilds comprising a few thousand or more animals within ten years, there simply wouldn’t be the numbers. This is particularly so for the European bison, which is a protected species and has never been ranched – and unlike the Koniks and Tauros can’t be bred as livestock to boost numbers.

Adapting policy to support rewilding

Common to all government conservation agencies is the notion of ‘competencies’ – the requirement that all public officials must uphold and act within their country’s laws and approved policy. Europe’s strong nature protection laws do not include clauses that allow for innovation in nature conservation and, as a result, government officials lack a mandate to support rewilding and, understandably, stick with existing rules and procedures. Added to this, European countries, in keeping with most nations around the world, have strict laws governing the keeping, transport, health and welfare of livestock. A key driver of these is reducing the risk of disease such as foot and mouth being transmitted from one herd to another, and ensuring that meat entering the food chain is safe. In Europe, horses and cattle are currently only known to policy-makers as livestock, so they have to be owned, the vet called in if they are ill, their carcasses disposed of, and the animals fenced to ensure they don’t cause accidents. In the case of cattle, calves must also be ear-tagged within three days of birth and entered into a database, and the transport of livestock recorded and permits obtained if this crosses borders. Added to this, many citizens are deeply concerned about animal welfare and have no image of cattle and horses other than as farm animals. De-domestication may be more a policy and cultural challenge than an ecological one.

The de-domestication of the horse is easier than cattle, but rebuilding numbers of European bison may be more difficult than both. This is because of their differing cultural and policy ‘identities’. Horses are not widely eaten in Europe and as a result are less regulated than cattle. In addition, there are populations (37 in total) of semi-wild horses across Europe, and cultural frames of galloping horses living free are prevalent. As a result, their de-domestication has ‘less far to travel’ culturally and ecologically.

Cattle, in contrast, have a large number of officials overseeing their management and have been so highly bred, with herd behaviours so modified, that it is hard to imagine them ever being wild. As a result, rewilders are beginning the de-domestication process within the constraints of livestock regulations, but pushing for flexibility in these to allow the recovery of natural herd structures and grazing. This is why the Tauros is presented as a new ‘wilded’ breed of cattle owned by the EWB. This positions EWB as a large livestock herd owner with the legitimate right to go to policy-makers and say: ‘We are rearing this breed of livestock in this way for these reasons and we would like you to interpret regulations to support our new livestock enterprise just like you would do for other livestock owners.’ This approach is beginning to pay off.

In a number of countries, the authorities have relaxed the requirement to ear-tag calves from within three days to within the first year, and Rewilding Europe has now started working with the European Commission to explore the feasibility of extending European livestock subsidies to wilded herds. If successful, this would be a massive gain because it would generate income for scaling up natural grazing. Furthermore, in European countries with a more socialist heritage, rights to graze and hunt are owned and leased by the state. With the decline of marginal agriculture mentioned earlier, grazing rights are increasingly becoming available; together with the recognition of wilded breeds by policy-makers, this could generate the elusive blend of wildlife needs – access to land, policy buy-in, megafauna, and finance. Counterintuitively, keeping de-domesticated analogues of aurochs and tarpan within the ‘livestock’ domain of policy, rather than pushing for them to be recognised as wild species, could enable the scaling up of rewilding with these species in Europe. It would also make the EU’s Common Agricultural Policy just that little bit saner!

Bison rewilding

In North America, bison populations have recovered from a low of 325 in 1884 to over 360,000 today, a large proportion of which are privately owned. The prospect for rebuilding European bison populations to comparable levels is not so encouraging. In Europe, the bison is a cultural relic: an orphan species locked within strict and out-of-date policy institutions. Unlike cattle and horses, bison lacked the traits necessary for easy domestication. They were already rare by the 8th century, and survived into modern times in the hunting reserves of European royalty. However, by the end of the 19th century only two wild populations survived, one in Białowieża forest in Poland and one in the west Caucasus Mountains of Russia, between the Black and Caspian seas. Sadly, the turmoil in Europe around the First World War led to the demise of both populations, and only 54 animals survived in zoological gardens – and these were all descended from just twelve individuals. This is about as close to extinction as it gets!

Efforts to recover the European bison began in Poland in 1924. The goal initially was to coordinate and expand breeding in zoos and private collections and to restore the genetic purity of the species (there had been some inbreeding with North American bison). By 1952, numbers were sufficient to begin the establishment of free-living herds, first in Białowieża forest and then in Belarus and Ukraine. Unfortunately, many animals from the Ukraine and Belarus populations were poached during the instability following the collapse of the Soviet Union, such that by 1990 the population was still only 2,000. In 2004 the conservation of the European bison was put on a more formal footing with a species survival plan prepared by an expert group and published by the International Union for Conservation of Nature (IUCN). The plan’s lead author was Zdzisław Pucek from the Polish Academy of Sciences and, in keeping with the prevailing view of the natural vegetation of Europe and Polish reintroduction practice, he concluded that the European bison was a forest species and future reintroduction should therefore be into suitable forest areas.

This is a classic case of the circular reasoning challenged by Frans Vera (discussed in Chapter 3). In 2012 an international team of scientists comprising Joris Cromsigt (Sweden) Graham Kerley (South Africa) and Rafał Kowalczyk (Poland) published two scientific papers arguing that the European bison was a refuge species: that over the centuries, human hunting and agricultural activities had pushed it out of grasslands and it had found refuge in remote forests. They suggested that European bison were forced to live in sub-optimal forest habitats and, by implication, the prospects for recovering the population are also sub-optimal.

This argument is given credence by the fact that the herd in Białowieża forest needs supplementary feeding to survive the winter, while a herd introduced into a 200 ha area of grassy sand dunes in the Netherlands is thriving without any feeding. In addition, all large forests in Europe are managed by foresters and his means that bison reintroductions must align with their ideas of managing herbivores within the ‘carrying capacity’ of a forest – meaning population numbers that do not damage the structure of forests from the perspectives of timber production. As a result, 40 bison are culled each year by Polish foresters.

There are a now approximately 7,000 European bison. Since the setback caused by the collapse of the Soviet Union, conservation groups have achieved an average annual growth rate of 5.1 per cent. This is lower than the 5.42 per cent growth rate achieved in the US with a commercial ranching approach, where 63,000 bison are currently harvested each year. In the region of 1,000 European bison are culled annually because zoos and nature parks lack the space to keep them and there are no available forests where they can be reintroduced. New rewilding initiatives are reintroducing bison to open wood-pasture landscapes in the southern Carpathians in Romania and the Rhodope Mountains in Bulgaria: two countries with large wild areas where traditional herding is in decline. However, progress is slow due to regulatory friction.

When countries join the European Union, they are required to adopt EU nature directives that classify the bison as a protected species. National governments are supposed to align their nature laws with these directives, but in the case of the bison this can be quite complicated. In some countries it is classed as extinct or ‘never native’, and in others it is still classed as a game species. Added to this, bison can carry livestock diseases such as foot and mouth and TB, so the agricultural lobby is not particularly enthusiastic about the idea of the return of wild herds that might interact with domestic herds, and the conservationists with their obsession with notions of genetic purity and ‘wildness’ have never thought of ranching as part of the species recovery plan. All this amounts to huge difficulties in obtaining the necessary permits to release bison into the regions of Europe where the collapse of traditional herding and agriculture offers opportunities for rewilding.

In addition, sources of bison for reintroduction are few, restricted to zoos and nature parks in western Europe. As a result, bison destined for eastern Europe must be trucked across the borders of several countries and have transport and veterinary certificates that ensure they do not carry diseases that could affect domestic livestock. To obtain these certificates, bison must be treated for these diseases before travel. This wipes out many important gut bacteria such that when they arrive at their new home, already out of condition from a long journey, they lack the microbial ecosystems to digest the unfamiliar vegetation. Added to this, they need to be kept in veterinary enclosures for six months or a year. This means that reintroduction teams must source hay to feed bison after arrival, which adds to the difficulty of transitioning them to eat local grasses, herbs and shrubs and results in higher than necessary mortality. Overcoming the barriers to bison rewilding in Europe will not be easy. A pragmatic approach would be to relax the rules to allow European farmers interested in bison ranching to buy surplus animals and build a ranched population from which animals could be bought for release as society comes to embrace rewilding ideas.

Beavers in Britain

The regulatory barriers to rewilding introductions are particularly stark in Britain, as shown by the case of the beaver. The beaver became extinct in Britain in the 16th century and in the Netherlands at the beginning of the 19th century, and survived only in very small numbers in France and Germany. However, thanks to reintroductions starting in the late 1980s there are now an estimated 14,000 beavers in France, 25,000 in Germany and over 3,000 in the Netherlands. In Britain, government conservation authorities have been much more conservative. At the time of writing there are only about twelve approved trials, and government officials are being pushed into action by a number of private and ‘guerrilla’ reintroductions.

The problem is rooted in British conservation law, which is based on schedules (lists) of protected species, invasive species and non-native species. Because the beaver was absent from the UK when these were compiled, there is no ‘standing advice’ on procedures that government nature conservation officials should follow. Put another way, if they allow beaver reintroductions, they have nothing to fall back on if others object. The bureaucratic response is to approve trials in order to build the evidence that will enable a cost–benefit and risk–opportunity analysis of the outcome of beaver reintroduction. This process is slow and the focus on building evidence for single species might generate new regulations with uncertain value for broader rewilding goals.

Monitoring rewilding

The growing number of rewilding initiatives has prompted some scientists to call for a practical framework for monitoring and evaluating rewilding projects. In 2018, a group of UK ecologists led by Nathalie Pettorelli of the Zoological Society of London published a paper pointing out that there are uncertainties and difficulties associated with rewilding and arguing that ‘the evidence available for facilitating sound decision-making remains elusive’. At present, rewilding initiatives are guided by a blend of vision and logical reasoning based on theoretical propositions. To date there is little empirical (factual) evidence suited to a robust understanding of links between rewilding actions and impacts, the risks associated with rewilding and the social costs and benefits involved.

Developing a framework for monitoring and evaluating rewilding is no simple matter. As we have described, rewilding practice is about restoring dynamic interactions between the biological and physical components of ecosystems and allowing nature to take its course. The rewilding action philosophy explicitly seeks to restore and embrace uncertainty in nature and to intervene only when competing interests needs to be managed. This will require a new approach to monitoring and a willingness to move away from traditions of measuring species population trends, changes in the proportions of different species in a habitat, or the degree of habitat fragmentation and connectivity across a landscape.

Fortunately, the rise of rewilding has coincided with a step-change in our ability to sense, measure and analyse different attributes of nature. The last decade has seen breathtaking advances in the power and affordability of computers and sensors, including radar, sonar, visual, thermal, chemical, seismic and acoustic sensors. Miniaturisation means that data can now be automatically collected from sensors incorporated in smartphones or mounted on drones and even bees! Furthermore, the roll-out of the mobile internet is making it easier to gather and share data collected from sensors in nature. There is now a tide of innovation in the disciplines of engineering, technology, computation and remote sensing and this is flowing into conservation science and, increasingly, rewilding. Technology offers the prospect of new approaches suited to monitoring rewilding and managing its impacts, as the following examples illustrate.

Earlier, we mentioned the need to feed hay to reintroduced bison during their quarantine phase. This hay-eating habit means that released bison have a tendency to raid haystacks during the winter, causing annoyance and financial losses to local farmers. In the southern Carpathians of Romania, the local WWF team is experimenting with an innovative use of technology to manage the problem. They have fitted bison with small GPS tags and created virtual (GPS) boundaries around villages. If a bison crosses the virtual fence, an alert is automatically sent to a local ranger and the time, date and the bison’s unique identity are transmitted to blockchain ledger. The idea is that villagers can then submit a photo of any bison damage (with a date and location stamp from their smartphone) and, if the two match, receive an automatic compensation payment. The beauty of this system is that it generates data on bison movements, the response rates and effectiveness of rangers, and the human cost of bison reintroduction. It is also highly adaptable. For instance, ear-tag GPS devices that incorporate an irritating buzz and electric shock are becoming available, turning virtual boundaries into easily reconfigurable virtual electric fences.

In North America scientists have equipped bison with collars that transmit their location to satellites in order to track their movements and grazing habitats across an area of 125,000 hectares. The data generated enables analysts to quantify the impact of bison grazing on the grasslands and the extent to which they compete with cattle. This particular study revealed little competition for grazing between bison and cattle, thereby alleviating the concerns of livestock interests and opening the way for restoring bison herds at an ecologically meaningful scale.

Several satellites carry arrays of powerful radar, optical and other sensors able to support high-resolution analysis of different ecological parameters such as vegetation type, photosynthesis and CO₂ emissions. The cost of access to high-resolution satellite imagery is coming within the realm of conservation budgets and offers the opportunity to monitor the impacts of rewilding at the scale of landscape and regions.

Before satellites, remote sensing was done via aerial photography. The appearance of low-cost consumer drones with high-resolution cameras is making orthogrammetry – the science of generating measurement from mosaics of photographs – possible for the managers of rewilding areas. Drones can be programmed via a smartphone app to take photographs along ‘lawn-mower’ flight paths from which stitching programs can produce 3D images. Using this technique, a UK team were able to measure fine-scale changes within an ecosystem supporting reintroduced beavers, and to demonstrate the positive impact they were having on their environment. Drone orthogrammetry opens the prospect of generating metrics of dynamic ecosystems, such as vegetation structure, and random disturbance events (e.g. bison wallows). At present such metrics can only be generated by costly commercial software, but this is likely to be overcome as the demand for monitoring grows in line with more rewilded areas.

These examples offer a tantalising view of the future of both rewilding and conservation monitoring more generally. Rewilding is characterised by a spirit of innovation in ecological theory and practice, as we have seen. As this ethos begins to interplay with the advances in technology illustrated above, and with broader developments in artificial intelligence and blockchain technology, we expect novel and as yet unimagined solutions to the challenges of monitoring dynamic ecosystems on their uncertain and self-willed pathways to recovery.

Rewilding needs to be pragmatic

We hope this chapter has conveyed something of the nuance and complexity of putting rewilding ideas into action. Opportunities for rewilding are opening up and philanthropic foundations are increasing their funding for the growing number of rewilded areas. However, rewilding is a form of land use – and one that requires significant areas in order to effectively rebuild trophic complexity and natural disturbance and dispersal. If the area of rewilding is to grow, it must ultimately serve the interests of those who own land, and who influence and control how it is managed. Jacobus du P. Bothma of the University of Pretoria describes post-apartheid South Africa as ‘the scene of one of the greatest reversals of fortune ever seen in wildlife conservation’. This happened because wildlife recovery served the financial interests of farmers better than agriculture, as we have seen. For rewilding to scale up, it must be framed and practised in ways that align with the interests of citizens, politicians, policy-makers, landowners and groups seeking to influence the future of the land economy.

The new political discourse of nature-based solutions offers an opportunity to do just this and, as described earlier in the chapter, European rewilders are actively developing rewilding approaches that address issues such as climate change, flooding, wildfires and rural depopulation. In 2019, a coalition of leading rewilding groups went a step further by launching a call to action for a wilder Europe. They urged progressive professionals in different sectors to join with rewilders to co-design approaches to recover nature and at the same time deliver the responsibilities of their sector. This willingness to enter into dialogue and innovate at the boundaries of nature and society is coming to characterise rewilding. In our view it increases the likelihood that rewilding will scale up, but it also means that more versions or ‘shades’ of rewilding will emerge in the future.

9

REWILDING – TEN PREDICTIONS FOR THE FUTURE

The journey so far

In this book we have explored the ‘hot science’ of rewilding. We have discussed how different scientific methods and practical actions are producing a dynamic interplay that is questioning widely held views and generating new visions of the possible in the realm of conservation. We hope that we have helped answer the question of what rewilding is, and how it differs from previous approaches to nature conservation. Our view is that rewilding refers to ‘spaces of innovation’ in conservation philosophy, science and management, characterised by a desire to restore ecosystem processes at various scales, often through the introduction of functional species and restoration of natural disturbance and dispersal.

As definitions go, this one is quite broad and may lack the level of technical detail desired by scientists. Equally, the phrase ‘spaces of innovation’ will likely sound too vague for many natural scientists but, in our view, it is this very openness that captures its significance. Rewilding connotes processes of becoming and recovery. We believe rewilding’s appearance and rapid adoption in science and popular culture has happened because it resonates with an emerging zeitgeist. This might best be described as a spirit of reassessment, creativity, pragmatism, and a desire for hope that is a consequence of rapid, and often worrying, scientific, technological, social, political and environmental change. This zeitgeist is causing nature-minded people to come together and create spaces where new concepts and techniques can be tested and refined.

These spaces of innovation in nature conservation have emerged organically, and we have tried to capture the diversity of rewilding initiatives along with the scientific principles that are increasingly common to all. This review of rewilding science and practice suggests that the concept of rewilding has evolved significantly since it was first introduced in the context of a North American wildlands strategy with its focus on predators and large, connected landscapes. As we have seen, rewilding science now emphasises new insights on the co-evolution of large herbivores and grassland biomes and the downgrading effects that historic extinctions and domestication have had on ecosystems. As a result of this longer-term view on ecological histories and change, rewilding is rejecting established scientific practices of cataloguing, protecting and restoring past natural baselines, in favour of a more flexible approach that takes inspiration from multiple past states, and focuses on restoring lost or weakened ecological processes. Because this approach has never been attempted before, it requires innovation in science, policy and practice. It also creates the opportunity to design rewilding in ways that offer nature-based solutions to contemporary challenges.

Rewilding science and practice is still new and only just beginning the uncertain journey towards ecological recovery. However, we believe there is a clear direction of travel, and so to conclude the book we offer the following predictions for developments in rewilding that may characterise the next decade. Of course, as the popular saying goes, ‘Prediction is difficult, especially about the future’, but we hope these new horizons will help stimulate discussion and action.

Rewilding creates a positive and hopeful environmental movement

In Chapter 7 we introduced the possibility that rewilding is giving rise to a new environmental narrative, one that is hopeful, pragmatic and empowering. This is already becoming evident in the media interest in rewilding and the growing enthusiasm for the concept in many domains of society. As the outcomes of rewilding initiatives become more widely known, as communication of the results becomes more inclusive and inspiring, and as rewilding establishes its scientific and policy credentials, we predict that people from all walks of life will mobilise behind rewilding as a movement for positive change. This will be at a scale where conservation regains its position as a cultural force with the power to shape societal futures. Just as the 20th-century conservation movement put wildlife at the centre of popular culture, leading to the creation of national parks and the enduring appeal of wildlife documentaries, we expect that rewilding will elevate nature recovery as a force shaping 21st-century culture.

In the last half-century, the values promoted by the conservation movement were subsumed within environmentalism – a more politically charged doctrine full of doom and gloom that argues that saving the environment requires moral resolve, limiting economic growth, and abstaining from foreign holidays, eating meat and exploiting nature. Rewilding, in contrast, recognises the importance of innovation, technology, economic adaptation and grounded action. It restates the prospect of a better future for all, and in so doing rewilding will empower the conservation movement with a new spirit, confidence and ambition. Over time we suggest that conservation will return to its social movement origins – a broad-based coalition of people and organisations seeking to govern the relationship between human society and nature and create a more sustainable world. However, this will not be the conservation movement of old which sought to protect nature from humanity’s harmful ways. It will be a new movement that seeks to recover ecosystems and humanity’s place within them. In the mid-20th century the nature movement dropped the term ‘preservation’ in favour of ‘conservation’ to reflect a new emphasis on the sustainable use and management of natural resources. As rewilding gains momentum we predict that a new term will gain ascendancy over ‘conservation’ and ‘environmentalism’. ‘Rewilding’ is, without doubt, the current front runner.

Return of the mega-herbivores

The key message of this book is that the scientific argument for restoring mega-herbivore guilds is compelling and it is beginning to happen in Europe and America. We think that this trend will accelerate and expand to other continents. We predict that Europe will lead the way. This is because rural depopulation and the decline of traditional agriculture are creating large areas of land in need of a new future. In addition, as discussed in Chapter 8, there are strong economic reasons for nature-based solutions which will drive the desire to restore mega-herbivore guilds in Europe, particularly where they have survived either as domestic species or in low numbers. As public and policy support grows for rewilding, so will the demand for herds of Tauros, wild horses and bison.

We predict that in order to accelerate the growth curve of populations of these species, forms of commercial breeding and ranching will develop. Indeed, we envisage that a new ‘kept wild’ category of animals will emerge with a set of policies suited to mega-herbivores. Such polices might include exemptions from livestock and transport regulations in and between designated areas, a right of ownership and a set of associated responsibilities. This will be supported by regulations enabling the sale of harvestable products. South Africa has gone some way down this route, demonstrating a transition from farming to wildlife ranching with benefits for people, the economy, wildlife and ecosystems. The return of mega-herbivores to the European continent will consolidate and expand the recovery of carnivores and in some areas will create wildlife spectacles that rival those of Africa.

The recovery of the European megafauna ecosystems will inspire other nations to similar efforts and will also provide a rich resource of expertise and knowledge for conservationists on other continents. Despite mega-herbivores not traditionally being seen as charismatic in the same way as big cats or primates, we predict that in the next ten years mega-herbivore conservation will assume significant levels of scientific prestige and funding, and public interest and appreciation of them will grow. We anticipate a new interest in rewilding landscapes in Indochina and south-east Asia, where the region’s mega-herbivores are surviving as isolated species on the very edge of extinction. In the Philippines, the Tamaraw Conservation Programme (TCP) has recovered the population of this dwarf species of cattle from under 200 in the year 2000 to over 500 today, demonstrating what is possible. We believe the step-change will come as Asian conservationists engage with the new science of rewilding and in particular the idea that their long list of endangered mega-herbivores – the kouprey, anoa, saola, gaur, banteng (all wild cattle) and Javan and Sumatra rhino – are all ‘refugee’ species. Like the European bison, they have been pushed into sub-optimal forest habitats due to a combination of human persecution and climate change. Projects to restore grassland–forest–megafauna systems in Thailand, Cambodia, Sumatra and the Philippines would likely have huge appeal for citizens of the region’s mega-cities, and would represent a serious tourism-based business opportunity for entrepreneurs. In this book we have barely referred to Indochina and south-east Asia. We do not think this will be the case for a book on rewilding written in 2030.

Rewilding becomes mainstream

Rewilding has generated controversy and dissent in scientific circles, within conservation organisations, from citizens concerned with animal welfare and from communities who feel their lifestyle threatened by rewilding visions. The media have jumped on proposals to reintroduce carnivores such as wolves, bears and lynx and framed these in ways to inflame deep-seated fears and generate the polarised debates that make for good copy. As discussed in Chapter 7, rewilders themselves have at times been insensitive or naive to cultural sensibilities, leading to deep resentments. In the UK, rewilding debates have been particularly intense, leading conservation organisations such as WWF, the National Trust and the RSPB to avoid using the ‘R’ word for fear that it may alienate sections of their broad membership base.

We believe that the intensity of controversies and debate will dissipate, and rewilding will move into the cultural and policy mainstream. Indeed, we would argue that rewilding is already on the cusp of entering the cultural mainstream. It is inspiring a raft of popular ‘eco-optimism’ books which are introducing rewilding to a general readership. One of the most significant is Isabella Tree’s Wilding, which hit the bestseller list and led to appearances on prestigious radio and TV shows. As a result, people who took no particular interest in nature are reading it as their first introduction to conservation ideas. Fundamentally, rewilding offers people stories of redemption, reconnection, hope and discovery. We believe the rewilding story is too compelling to ignore and that the wildlife media – film-makers, writers, journalists and editors – will embrace it and extend its popular reach.

Rewilding is a little further from the policy mainstream, but we think this will change quickly as the potential of rewilding as a nature-based solution becomes better known and better evidenced. For example, within the next few years we expect the publication of scientific research comparing the levels of carbon sequestered by rewilded (wood-pasture) land systems with those of reforested lands. In brief, rewilded land systems have the potential to sequester carbon in their soils, in woodland groves and in the expanded animal fauna. Soils store more carbon than all terrestrial plants (including rainforests) and studies show that prolonged cultivation causes soils to lose between 20 per cent and 65 per cent of their soil organic carbon (SOC). When degraded agricultural lands undergo ecological restoration, they remove atmospheric CO₂ and store it as SOC; and large herbivores grazing on fast-growing grasses may accelerate the return of carbon to the soil via their dung and associated recovery of the soil biota.

Politicians are responding to public worry over climate breakdown with pledges to plant millions of trees. However, several scientists are pointing out that grasslands may be more reliable carbon sinks than trees in the long term because the captured carbon is stored in their soils. In contrast, trees store carbon in their woody biomass and leaves, and if they catch fire this is released back into the atmosphere. As more studies contrast the multiple benefits of wood-pastures with those of simple tree planting, we predict that decision-makers will realise that rewilded land systems offer the potential to simultaneously address a suite of concerns – climate change, biodiversity loss, flood management, soil health, ethical food production and rural depopulation – and will gradually put in place the polices and incentives to support wider adoption.

This is not to say that debate will disappear. However, we predict that the debate will mature as it becomes more evidence-based. As a new term, rewilding became something of a straw man for groups and individuals looking to gain political advantage or renewed attention for historic injustices. These included claims that rewilders were engaged in land-grabbing, neo-colonial practices of dispossession, and undermining agricultural livelihoods. Now that a portfolio of rewilding practice and associated principles are available for scrutiny, such misrepresentations or exaggerations will be difficult to maintain. In addition, the rewilding ethos increasingly emphasises innovation, pragmatism and principles of co-production. In short, it is not a purist form of conservation.

In the next decade, we anticipate that the rewilding debates will focus more on the question of trade-offs and risks. For example, as rewilding initiatives begin to scale up, we expect there to be more discussion on the consequences of rewilding for rare and specialist species and for the spread of invasive species and pathogens. Such debate is important and should be welcomed, because any new approach needs critical challenge in order to build buy-in and to have an impact.

Rewilding science programmes: from debate to data

Rewilding is currently theory-led rather than evidence-based. This book has been about the new scientific and practical insights that are causing a reassessment of what has been taken for granted in ecology – that the natural vegetation of Europe is closed forest – and the resolution of long-standing debates, notably on the respective roles of climate and humans in the demise of megafauna towards the end of the Pleistocene. We believe that rewilding signifies the beginnings of a paradigm shift in conservation science, policy and practice. However, a huge amount of detail is missing. The new functionalist paradigm – shifting the focus from protecting biodiversity, endangered species and habitats to rebuilding ecosystem complexity through restoring guilds of functional species along with natural disturbance and connectivity – is potentially transformative. But there are still huge unknowns on how to go about putting it into practice, on the potential risks involved and the extent to which rewilding will deliver ‘co-benefits’ such as carbon sequestration and new nature-based economies.

New science programmes are emerging to address these questions and we predict that they will increase in scope and ambition in the next decade. A 2018 special issue of the Proceedings of the Royal Society, edited by Elisabeth S. Bakker of the Netherlands Institute of Ecology and Jens-Christian Svenning of Aarhus University, brought together a collection of papers that outlined the contours of the rewilding research agenda. Two big themes were evident. The first was to understand the ecological impact of rewilding herbivores in different land use types. This theme aims to test the hypothesis that rewilding could have positive effects for biodiversity, and has two strands: i) investigating the impacts of rewilding on soil and vegetation structure and associated biodiversity; and ii) investigating the extent to which rewilding suppresses or aids the spread of invasive species and pathogens. Recall that rewilding aims to restore dispersal and connectivity across landscapes, but this could also aid the spread of invasive species and diseases that can cause havoc in our weakened ecosystems.

A second theme concerns the question of which functional species to introduce where, in what order and in what numbers? This is an urgent and pressing question for rewilding practitioners, who recognise that different settings have different mixes of species and ecological histories and are therefore likely to respond differently to the addition of different functional species.

Take for example an area of grassland and scrub grazed for decades by a mix of rabbits, roe deer and domestic sheep but that is succeeding to forest as shepherding declines. What would be the best strategy for rebuilding trophic complexity and grazing dynamics? Is it OK to introduce one species at a time, such as wild horses and then bison, based on the availability of animals and funds? Or will ecosystems respond better if a guild of larger herbivores, for instance red deer, wild horses and Tauros, are introduced at the same time? And what about sheep and goats? Where, if anywhere, do these grazers fit into new rewilded ecosystems? These are complex questions and we expect scientists with expertise in complexity theory and computer modelling to partner with ecologists to explore the ecological effects of different introduction scenarios. As more becomes known about the physical and behaviour traits of different functional species and the ecological impacts of their introductions, we anticipate that these models will develop in sophistication and practitioners will assume a more diagnostic and design-engineering approach to rewilding.

We have already mentioned the relationship between rewilding and climate science and we predict that this will become a significant research area, along with research on the extent to which rewilding can address climate change and help solve other policy challenges such as the increase of wildfires and rural depopulation. We predict the appearance of large-scale and long-term rewilding science experiments to rigorously test the cost-effectiveness of rewilding as a nature-based solution. For example, in 2020 a team from Oxford University (including this book’s first author) outlined a ten-year science programme to properly test the Pleistocene Park hypothesis that Arctic rewilding could reduce emissions from permafrost thawing. The team estimate that the programme would cost $125m, which might sound a lot, but is significantly less than the $486m spent by the European Union on carbon capture technology research in the last decade (which has achieved little according to the EU’s auditors). We expect other scientists to follow suit and put forward visions for exploratory rewilding research programmes that might deliver major public benefit.

One final prediction, or perhaps hope, for rewilding research is that advances in ancient DNA research will extend to rewilding. A theme of this book has been the interdisciplinary nature of rewilding science and the new techniques that are coming on stream thanks to advances in technology. Perhaps more than anything, rewilding science is about developing a clearer picture of the impacts of humanity on ecosystems over time, and drawing on these to rebuild ecosystems where both people and wildlife can ‘live well’. In the last few decades the science of ancient DNA – the ability to extract DNA from ancient remains and trace the mixing and movements of populations over time – has revolutionised knowledge of the evolution and spread of modern humans. We predict that scientists will start to apply such techniques to the remains of late Pleistocene and early Holocene herbivores, and that, combining those insights with new understanding of human dispersal, will refine the ‘overkill’ hypothesis and deepen our knowledge of the impacts of humanity on ecosystems and on the Earth system more generally.

Rewilding by design

One of the defining features of the new century is the widespread migration of rural people to urban areas. The United Nations estimates that around 55 per cent of the world’s population now lives in cities, and predicts that this will rise to 68 per cent by 2050. Fifty years ago, 63 per cent of the world’s population was rural, but 2006 marked the point when the balance between rural and urban shifted and the future of humanity became ever more urbanised. The figures differ by region and continent, but the trend is the same everywhere – and this transition is accompanied by a polarisation of land use. On the one hand, productive land is being managed more intensively with bigger machines and better technology to produce the food and resources required by a growing human population. On the other hand, land that is marginal for agriculture or forestry, by virtue of being too dry, infertile or steep, is being abandoned and reverting to nature.

The spontaneous recovery of vegetation is increasingly referred to as passive rewilding – rewilding where nature finds its own way forward from whatever state it was left in following human abandonment. In temperate regions this is likely to result in varying degrees of tree cover, which will be welcomed by many. But elsewhere it will likely result in wildlife-poor ecosystems such as the alang-alang grasslands of south-east Asia or the flammable scrublands we discussed in Chapter 8. Rewilding is, in essence, a type of ecological engineering, the planned practice of restoring trophic complexity and natural dynamics to set ecosystems on a trajectory of recovery. As we have explained, rewilding is increasingly being aligned with the policy concept of nature-based solutions: the idea that we can work with restored forces of nature to adapt to social and environmental change. We predict that this idea will take off and that notions of land abandonment and passive rewilding will give way to planned land system change based on active rewilding principles. We anticipate that the momentum will grow for transitioning marginal agricultural areas to functioning ecosystems that take inspiration from the past but that are designed and ‘steered’ to generate multiple forms of future value for human societies – from carbon sequestration and natural flood management, to revitalising cultural identity and improving public health.

Urban rewilding

Rewilding is not only happening in areas where human impacts are receding. We are also witnessing the emergence of urban rewilding initiatives and we predict that these will multiply as rewilding stories inspire urban citizens with a desire to reconnect with nature. We anticipate that urban rewilding will assume a different, yet complementary, form of rewilding in less densely populated landscapes, and that over time flows between rural and urban rewilding will magnify the impact of rewilding as a cultural movement.

During the next decade we anticipate that rewilding will reinvigorate and extend the urban conservation movement of the 1980s. This inspired progressive cities in western Europe, America and also Singapore to integrate nature protection and restoration in the planning of urban greenspace as part of city regeneration. Presently, most urban rewilding projects are focusing on rekindling older partnerships with local authorities to protect and create wild areas, bringing back wildlife and organising activities to connect citizens with their local nature. In the next ten years we expect that public enthusiasm for rewilding will connect with progressive urban environmental and health planning to enhance the liveability of cities.

Blogs and opinion pieces exploring the ideas for rewilding cities are proliferating on the web and focus on two themes – the design of buildings and green infrastructure and the quality of urban living. One significant difference between the 1980s and now is the interest in green or ‘cool’ roofs. Concrete-frame construction has peppered our cities with elevated flat roofs, and vegetating these is a means to reduce urban hotspots, pollution, rainwater run-off and heating costs, and to create opportunities for new gardens, urban farms and wild areas.

Green roofs would massively increase the space available for nature in cities and create the possibility of an urban form of rewilding that could restore ecological connectivity and dispersal of species in cities, as well as ecological processes such as pollination and seed dispersal. The concept of ecospace described in Chapter 5 offers a valuable theoretical framework to design functioning urban ecosystems constructed from discrete multi-level spaces. In total these ecosystems are unlikely to resemble anything that has gone before, and we anticipate that they will be designed to enhance species that we love – swifts, butterflies, flowering trees, etc. – and reduce the abundance of species that cause problems, such as pollen-producing plants, rats and pigeons. Rewilded urban ecosystems will be beautiful but sanitised.

We also anticipate that citizens will be actively engaged with the design and management of rewilded urban spaces. A growing body of scientific evidence confirms what many of us intuitively know – that contact with nature improves our mood, reduces anxiety and stress, and boosts our immune system. As soon as the term rewilding entered the public consciousness it was picked up by those seeking a greater sense of connectedness, mindfulness and autonomy – and a little less conformity. Phrases such as ‘rewilding the self’ and ‘rewilding the mind’ express aspirations for new forms of urban living where nature is built into cities. Urban rewilding creates new opportunities for democratic participation and community action that is constructive and not overtly political. We predict that urban rewilding movements will emerge and flourish in cities around the world.

The next decade is expected to see significant progress towards the ideal of Smart Cities – urban areas with buildings, infrastructure, vehicles and people equipped with the Internet of Things (IoT), sensors that stream data to centres where it is analysed to manage the city more effectively. Our hope is that urban rewilders contribute ideas to the development of the Internet of Ecological Things (IoET) and generate Smart City visions where citizens can connect with natural sights, sounds and rhythms both directly and indirectly via their smartphones, smart speaker devices and whatever else may come along. It could be that much of the initial design and development of techniques to monitor ecological recovery happens in urban settings.

Distributed networks of rewilding action

A message of this book is that rewilding is underpinned by an increasingly coherent body of science and agreed-upon principles, but that it results in different expression by different groups of people in different contexts. In short, there are many versions of rewilding and we predict that the flexibility and inspiration this provides will lead to the emergence of many new rewilding start-ups that are rooted locally but coordinate through informal knowledge and skill-sharing.

Put another way, we predict that the future organisational form of rewilding will be a decentralised network of small- to medium-sized enterprises. This will be quite different to the centralised and somewhat bureaucratic model of conservation that emerged in the late 20th century and still dominates today. At the time, a range of factors created an imperative for conservation organisations to centralise in order to grow and have impact. These included the cost of computing, communications and travel, the limited geographic reach of networks providing access to decision-makers and funders, and the small pool of trained conservation professionals. Household name organisations such as WWF, BirdLife International, Conservation International and The Nature Conservancy all built successful organisations and brands by centralising and collaborating with governments to produce a set of laws, policies, standards and targets to ‘mainstream’ biodiversity into national and international development.

The imperatives to centralise have dissipated with the internet, the rise of powerful low-cost computation and the large number of people who have studied degrees in conservation science. Starting up a conservation initiative has never been easier, and we predict that, motivated by the rewilding spirit and empowered by technology, groups of entrepreneurial people will organise to develop and implement rewilding visions. We are already witnessing this, with some organisations specialising in rewilding communication, others in herd management, others in advisory support and others in area management. We expect this trend to continue and predict the emergence of a functional ‘ecosystem’ of rewilding enterprises.

Rewilding ripple effects

We predict that in the next twenty years we will see major sectors integrating rewilding and ecological recovery into their mission, approach and economic rationales. In Chapter 8 we described how this has already happened in river management in the Netherlands, and we anticipate that such rewilding schemes will catch on in other developed countries with highly engineered river systems.

Fisheries science (the academic study of managing and understanding commercial fish stocks) contributed a key conceptual principle to rewilding in the form of the shifting baseline syndrome – the reality that the slow degradation of ecosystems can go unnoticed because each new generation uses the nature they encounter in their youth as the reference point for ‘natural’ levels of ecological abundance and diversity. Rewilders and fishery scientists both understand the scale of declines in natural abundance and share a desire to recover natural river flows and fish populations. In the next decade we predict the formation of coalitions involving progressive fishery scientists and rewilders advocating for the restoration of migrations of fish such as salmon and sturgeon that live at sea and breed in fresh waters, and of fish such as eels that do the opposite. Initiatives such as the Pacific Salmon Restoration Programme on the US west coast share the same goals with rewilding: to remove old dams and, where this is not possible, improve fish passages (and lobby for reforms of industrial forestry in order to protect watersheds and river channels from damage). Combining the popular appeal of rewilding with the economic clout of fisheries management could further the aims of both commercial fishing and ecosystem recovery. It could also be a route to restoring the nutrient flows between the oceans and land described in Chapter 6.

Forestry is another sector where we expect to see the uptake of rewilding principles, although in a more diluted form. Foresters generally are not concerned with the recovery of animal populations, and the focus of their profession is the active management of nature rather than the restoration of self-willed ecosystems in need of much-reduced human intervention. Nonetheless, as Norman Dandy and Sophie Wynne-Jones argue in a 2019 issue of Forest Policy and Economics, there are a number of parallels between elements of forestry and rewilding science: they note that several UK projects aspire to restore natural forest, and that this forest restoration is giving more attention to the ecological connectivity, integrity and resilience of forest lands, all of which matter to rewilders. They call for a more active dialogue between rewilders and foresters involved with forest restoration.

As the decade of ecosystem restoration gains momentum, we predict that rewilding science will influence the ways in which different sectors approach restoration. For example, among farmers there is growing interest in regenerative agriculture and pasture-fed livestock rearing. Both are based on agricultural principles and practices that restore soil fertility and micro-organisms and enhance biodiversity. Furthermore, sustainable meat production is likely to become a major topic of public discourse as lab-grown meat technology comes on stream and ‘bulk’ meat is replaced by culture-grown proteins. There seems to be scope for productive interchanges between proponents of rewilding and livestock farmers on ways to create land systems that produce high-quality premium meat through rewilding with free-range herbivores or pasture-fed livestock.

We expect that such dialogues will also happen between the different sectors of nature conservation. For example, although we mentioned the massive impact of humans on the marine system in Chapter 3, we have not discussed any marine rewilding projects. This is because it is not yet quite clear how rewilding differs or adds anything to long-established projects to protect marine megafauna and conserve and restore coral reefs, sea grass beds and other coastal systems. A lot of existing marine practices are already aligned with rewilding principles. For example, projects to remove crown-of-thorns starfish are kickstarting the recovery of coral reefs, and replanting mangroves is restoring fish nursery grounds and their coastal protection function. However, as the radical aspects of rewilding science become better known among marine conservationists, we predict that it will prompt the development of more ambitious visions for marine recovery.

Extreme rewilding

A theme of this book has been the role of pioneer rewilding projects in driving innovations in science and resetting public expectations of the possible. In the next decade or two we predict the emergence of more extreme and ambitious rewilding experiments – specifically, initiatives that recreate lost megafauna guilds from the nearest equivalent species available on our planet. These would fulfil a scientific function: for instance, we can only understand the impacts of Proboscidean extinction on South American forests by introducing an extant Proboscidean, e.g. the Asian elephant. The idea of introducing free-roaming rhinos to Australia, cheetahs to the American prairies, or lions to Europe would be hugely radical and controversial within conservation circles. However, such ideas might appeal to people less versed in conservation biogeography and used to visiting zoos and watching ‘hyper-wild’ nature documentaries. We would not be surprised to see the emergence of ‘rewilding parks’ – a development of the safari park where novel assemblies of functional species can live with limited management and where their ecosystem impacts can be studied, and where people can visit and experience potential natures of the future.

Such parks could interact with traditional efforts to save species by building back-up populations of critically endangered megafauna such as rhino, elephant, lions or tigers in safe zones outside of their normal range. Rewilding parks could extend the idea of wildlife banks that we talked about in Chapter 8, to include efforts to save wild populations as well as breed up a ‘pipeline’ of de-domesticated species for reintroduction. In the longer term, such parks might create the conditions for permanent introduction of megafauna herbivores and predators outside of their geographic range to restart, among other things, lost evolutionary processes.

If rewilding parks do come into being, they could well become the locus of de-extinction experiments. The idea of resurrecting extinct species such as the mammoth, sabre-toothed cat and woolly rhino has huge public appeal. As we have seen, a team led by George Church at Harvard University has been working for several years to recreate a mammoth-like animal, though Beth Shapiro has compellingly argued that cloning lost species is beyond the realms of scientific possibility and that such animals will come back only as bits of genetic material spliced into the DNA of existing species and expressed in hybrid creatures that may or may not look like the extinct species. De-extinction is on the extreme end of the rewilding spectrum and we hope it doesn’t go down that route. It would turn nature into a freak show, and this could undermine the transformative potential of more moderate versions of rewilding.

Nature surprises

Pioneering projects show that nature rebounds quickly and produces unexpected outcomes and fresh insights that surprise and delight. In previous chapters we have mentioned several: the ‘bounce back’ of endangered skinks on Île aux Aigrettes and Round Island in the Indian Ocean, the appearance in the Dutch river delta of aquatic habitats previously known only from nutrient-poor upland areas, and the realisation that the European bison may be a species of wood-pasture mosaics and not high forest, to name but a few. We predict that there will be many more as trophic complexity, natural disturbances and landscape connectivity are restored.

Predicting surprises is a mug’s game, but pondering on what might be is an enjoyable and motivational pastime nonetheless. If you have read this far, we hope you will find a moment to imagine what surprises rewilding could produce in natural areas you know and love. Several rewilders, amazed at the reappearance of smaller species thought to be extinct in a region, talk about landscapes having an ecological ‘memory’. We are coming to realise that species of beetle, moths, fungi and so forth may be hanging on in tiny populations that are too rare and scattered to be picked up by ecological monitoring, but when rewilding restores their ecospace they reappear like a long-lost memory.

Rewilding prompts new ways of looking at ecosystems, and we predict that in the next decade scientists will be surprised about what they have overlooked. For example, rewilding ideas prompted Brazilian ecologists to investigate reports of strange cave systems in their country. They realised that they were in fact ‘paleo-burrows’ – 1.5m-wide tunnels, some them hundreds of metres long, created by extinct giant ground sloths. Armed with this new knowledge, we predict that giant sloth burrows will be discovered in many more countries, and the associated publicity will cause nations to rethink their ecological histories and embrace rewilding approaches to conservation. More generally we anticipate that conservation scientists will be surprised that many endangered species are in fact those that evolved to fit the dynamic and varied habitats produced by the interactions of a now forgotten megafauna, vegetation and topography. As rewilded ecosystems re-expand and we witness anew the behaviours and life-cycles of once-endangered species, we may be surprised that we did not see the clues to their true ecological identities earlier.

But perhaps the biggest surprise will be just how quickly rewilded natures become normal, cherished and desired. In 1984, the American entomologist E.O. Wilson introduced the ‘biophilia’ hypothesis, which he described as the ‘innate urge [of humans] to affiliate with other forms of life’. Millennia of ecological downgrading have diminished our ability to connect with different life-forms and especially those that are closer to our level in terms of size, social behaviours and sentience. Rewilding offers the prospect of a new and fulfilling way to connect with nature. In a world where many people are increasingly finding the pursuit of material desires to be superficial and wanting, we predict a surprising level of enthusiasm for the ‘new wild’ of rewilding and the sense of connection and well-being it generates. We will be encouraged by how little ecological recovery costs, compared to other areas of public expenditure, and inspired at the new spirit of hope and confidence that rewilding imbues in people and in wider society.

FURTHER READING

The following is a selection of books and academic articles referred to in each chapter and which offer good starting points for students interested in delving deeper into the science discussed.

Chapter 1

Donlan, C.J., Berger, J., Bock, C.E., Bock, J.H., Burney, D.A., Estes, J.A., Foreman, D., Martin, P.S., Roemer, G.W., Smith, F.A., Soulé, M.E., and Greene, H.W., 2006. ‘Pleistocene rewilding: an optimistic agenda for twenty-first century conservation’. The American Naturalist, 168: 660–681.

Foreman, D., 2004. Rewilding North America: A Vision for Conservation in the 21st Century. Island Press.

Zimov, S.A., 2005. ‘Pleistocene Park: return of the mammoth’s ecosystem’. Science, 308: 796–798.

Chapter 2

Bond, W.J., 2005. ‘Large parts of the world are brown or black: a different view on the “Green World” hypothesis’. Journal of Vegetation Science, 16: 261–266.

Hofmann, R.R., 1989. ‘Evolutionary steps of ecophysiological adaptation and diversification of ruminants: a comparative view of their digestive system’. Oecologia, 78: 443–457.

Janis, C.M., 1993. ‘Tertiary mammal evolution in the context of changing climates, vegetation, and tectonic events’. Annual Review of Ecology and Systematics, 24: 467–500.

Shoshani, J., 1998. ‘Understanding proboscidean evolution: a formidable task’. Trends in Ecology & Evolution, 13: 480–487.

Strömberg, C.A., 2006. ‘Evolution of hypsodonty in equids: testing a hypothesis of adaptation’. Paleobiology, 32: 236–258.

Strömberg, C.A., 2011. ‘Evolution of grasses and grassland ecosystems’. Annual Review of Earth and Planetary Sciences, 39: 517–544.

Chapter 3

Araujo, B.B., Oliveira-Santos, L.G.R., Lima-Ribeiro, M.S., Diniz-Filho, J.A.F., and Fernandez, F.A., 2017. ‘Bigger kill than chill: The uneven roles of humans and climate on late Quaternary megafaunal extinctions’. Quaternary International, 431: 216–222.

Ceballos, G., Ehrlich, P.R., Barnosky, A.D., García, A., Pringle, R.M., and Palmer, T.M., 2015. ‘Accelerated modern human-induced species losses: Entering the sixth mass extinction’. Science Advances, 1: 1400253.

Dudgeon, D., Arthington, A.H., Gessner, M.O., Kawabata, Z.I., Knowler, D.J., Lévêque, C., Naiman, R.J., Prieur-Richard, A.H., Soto, D., Stiassny, M.L., and Sullivan, C.A., 2006. ‘Freshwater biodiversity: importance, threats, status and conservation challenges’. Biological Reviews, 81: 163–182.

Galetti, M., 2009. ‘Parks of the Pleistocene: recreating the Cerrado and the Pantanal with megafauna’. Natureza & Comservacão 2: 93–100.

Grill, G., Lehner, B., Thieme, M., Geenen, B., Tickner, D., Antonelli, F., Babu, S., Borrelli, P., Cheng, L., Crochetiere, H., and Macedo, H.E., et al., 2019. ‘Mapping the world’s free-flowing rivers’. Nature, 569: 215–221.

Grill, G., Lehner, B., Lumsdon, A.E., MacDonald, G.K., Zarfl, C., and Liermann, C.R., 2015. ‘An index-based framework for assessing patterns and trends in river fragmentation and flow regulation by global dams at multiple scales’. Environmental Research Letters, 10: 015001.

Guthrie, R.D., 2006. ‘New carbon dates link climatic change with human colonization and Pleistocene extinctions’. Nature, 441: 207–209.

Hallmann, C.A., Sorg, M., Jongejans, E., Siepel, H., Hofland, N., Schwan, H., Stenmans, W., Müller, A., Sumser, H., Hörren, T., Goulson, D., and de Kroon, H.E., 2017. ‘More than 75 percent decline over 27 years in total flying insect biomass in protected areas’. PLOS One, 12: 0185809.

Hingston, R.G.W., 1931. ‘Proposed British national parks for Africa’. Geographical Journal, 74: 401–428.

Martin, P.S., 2005. Twilight of the Mammoths: Ice Age Extinctions and the Rewilding of America. University of California Press.

MacArthur, R.H., and Wilson, E.O., 2001. The Theory of Island Biogeography. Princeton University Press.

Reich, D., 2018. Who We Are and How We Got Here: Ancient DNA and the New Science of the Human Past. Oxford University Press.

Rosenberg, K.V., Dokter, A.M., Blancher, P.J., Sauer, J.R., Smith, A.C., Smith, P.A., Stanton, J.C., Panjabi, A., Helft, L., Parr, M., and Marra, P.P., 2019. ‘Decline of the North American avifauna’. Science, 366: 120–124.

Sandom, C., Faurby, S., Sandel, B., and Svenning, J.C., 2014. ‘Global late Quaternary megafauna extinctions linked to humans, not climate change’. Proceedings of the Royal Society B: Biological Sciences, 281: 20133254.

Surovell, T.A., Pelton, S.R., Anderson-Sprecher, R., and Myers, A.D., 2016. ‘Test of Martin’s overkill hypothesis using radiocarbon dates on extinct megafauna’. Proceedings of the National Academy of Sciences, 113: 886–891.

Wroe, S., Field, J., Fullagar, R., and Jermin, L.S., 2004. ‘Megafaunal extinction in the late Quaternary and the global overkill hypothesis’. Alcheringa, 28: 291–331.

WWF & ZSL Living Planet Index. http://www.livingplanetindex.org/home/index

Chapter 4

Durrell, G., 2002. Golden Bats and Pink Pigeons. House of Stratus.

Falcón, W., and Hansen, D.M., 2018. ‘Island rewilding with giant tortoises in an era of climate change’. Philosophical Transactions of the Royal Society B: Biological Sciences, 373: 20170442.

Hansen, D.M., Donlan, C.J., Griffiths, C.J., and Campbell, K.J., 2010. ‘Ecological history and latent conservation potential: large and giant tortoises as a model for taxon substitutions’. Ecography, 33: 272–284.

Hansen, D.M., and Galetti, M., 2009. ‘The Forgotten Megafauna’. Science, 324: 42–43.

Lorimer, J., Sandom, C., Jepson, P., Doughty, C., Barua, M., and Kirby, K.J., 2015. ‘Rewilding: Science, practice, and politics’. Annual Review of Environment and Resources, 40: 39–62.

Mitchell, F.J.G., 2005. ‘How open were European primeval forests? Hypothesis testing using palaeoecological data’. Journal of Ecology, 93: 168–177.

Nogués-Bravo, D., Simberloff, D., Rahbek, C., and Sanders, N.J., 2016. ‘Rewilding is the new Pandora’s box in conservation’. Current Biology, 26: 87–91.

Ripple, W.J., and Beschta, R.L., 2012. ‘Trophic cascades in Yellowstone: the first 15 years after wolf reintroduction’. Biological Conservation, 145: 205–213.

Vera, F.W.M., 2000. Grazing Ecology and Forest History. CABI Publishing.

Vera, F.W.M., 2009. ‘Large-scale nature development – The Oostvaardersplassen’. British Wildlife, 20: 28.

Wolf, A., 2008. ‘The big thaw’. Stamford Magazine.

Zimov, S.A., 2005. ‘Pleistocene Park: return of the mammoth’s ecosystem’. Science, 308: 796–798.

Zimov, S.A., Zimov, N.S., Tikhonov, A.N., and Chapin, F.S., 2012. ‘Mammoth steppe: a high-productivity phenomenon’. Quaternary Science Review, 57: 26–45.

Chapter 5

Brunbjerg, A.K., Bruun, H.H., Moeslund, J.E., Sadler, J.P., Svenning, J.C., and Ejrnaes, R., 2017. ‘Ecospace: A unified framework for understanding variation in terrestrial biodiversity’. Basic and Applied Ecology, 18: 86–94.

Hayward, M.W., Scanlon, R.J., Callen, A., Howell, L.G., Klop-Toker, K.L., Di Blanco, Y., Balkenhol, N., Bugir, C.K., Campbell, L., Caravaggi, A., and Chalmers, A.C., et al., 2019. ‘Reintroducing rewilding to restoration – rejecting the search for novelty’. Biological Conservation, 233: 255–259.

Laundré, J.W., Hernández, L., and Ripple, W.J., 2010. ‘The landscape of fear: ecological implications of being afraid’. The Open Ecology Journal, 3: 1–7.

Perino, A., Pereira, H.M., Navarro, L.M., Fernández, N., Bullock, J.M., Ceauşu, S., Cortés-Avizanda, A., van Klink, R., Kuemmerle, T., Lomba, A., and Pe’er, G., et al., 2019. ‘Rewilding complex ecosystems’. Science, 364: eaav5570.

Rewilding Europe & ARK Nature, 2017. Cycle of Life: a New Way to Support Europe’s Scavengers. DOI: 10.26763/2017.01

Svenning, J.C., Pedersen, P.B., Donlan, C.J., Ejrnaes, R., Faurby, S., Galetti, M., Hansen, D.M., Sandel, B., Sandom, C.J., Terborgh, J.W., and Vera, F.W.M., 2016. ‘Science for a wilder Anthropocene: Synthesis and future directions for trophic rewilding research’. Proceedings of the National Academy of Sciences, 113: 898–906.

Chapter 6

Doughty, C.E., Wolf, A., and Field, C.B., 2010. ‘Biophysical feedbacks between the Pleistocene megafauna extinction and climate: The first human-induced global warming?’. Geophysical Research Letters, 37: 15.

Doughty, C.E., Wolf, A., and Malhi, Y., 2013. ‘The legacy of the Pleistocene megafauna extinctions on nutrient availability in Amazonia’. Nature Geoscience, 6: 761–764.

Doughty C.E., Roman, J., Faurby, S., Wolf, A., Haque, A., et al., 2016. ‘Global nutrient transport in a world of giants’. Proceedings of the National Academy of Sciences, 113: 868–873.

Janzen, D.H., and Martin, P.S., 1982. ‘Neotropical anachronisms: the fruits the gomphotheres ate’. Science, 215: 19–27.

Macias-Fauria, M., Jepson, P., Zimov, N., and Malhi, Y., 2020. ‘Pleistocene Arctic megafaunal ecological engineering as a natural climate solution?’. Philosophical Transactions of the Royal Society B, 375: 20190122.

Malhi, Y., Doughty, C.E., Galetti, M., Smith, F.A., Svenning, J.C., and Terborgh, J.W., 2016. ‘Megafauna and ecosystem function from the Pleistocene to the Anthropocene’. Proceedings of the National Academy of Sciences, 113: 838–846.

Wolf, A., Doughty, C.E., and Malhi, Y., 2013. ‘Lateral diffusion of nutrients by mammalian herbivores in terrestrial ecosystems’. PLOS One, 8: 71352.

Zimov, S.A., Schuur, E.A., and Chapin III, F.S., 2006. ‘Permafrost and the global carbon budget’. Science, 312: 1612–1613.

Chapter 7

Carson, R., 1962. Silent Spring. Houghton Mifflin Company.

Fairfield Osborn, H., 1948. Our Plundered Planet. Little, Brown and Company.

Goderie, R., Helmer, W., Kerkdijk-Otten, H., Widstrand, S., 2013. The Aurochs: Born to be Wild. Roodbont.

Goffman, E., 1974. Frame Analysis: An Essay on the Organization of Experience. Harvard University Press.

Greene, J.D., 2013. Moral Tribes: Emotion, Reason, and the Gap Between Us and Them. Penguin.

Jepson, P., 2019. ‘Recoverable Earth: a twenty-first century environmental narrative’. Ambio, 48: 123–130.

Kahneman, D., 2011. Thinking, Fast and Slow. Macmillan.

Monbiot, G., 2013. Feral: Searching for Enchantment on the Frontiers of Rewilding. Penguin UK.

Shapiro, B., 2015. How to Clone a Mammoth: the Science of De-extinction. Princeton University Press.

Tree, I., 2018. Wilding: The Return of Nature to a British Farm. Pan Macmillan.

Vogt, W., Baruch, B.M., and Freeman, S.I., 1948. Road to Survival. W. Sloane Associates.

Zamboni, T., Di Martino, S., and Jiménez-Pérez, I., 2017. ‘A review of a multispecies reintroduction to restore a large ecosystem: the Iberá Rewilding Program (Argentina)’. Perspectives in Ecology and Conservation, 15: 248–256.

Chapter 8

Jepson, P., Schepers, F., and Helmer, W., 2018. ‘Governing with nature: a European perspective on putting rewilding principles into practice’. Philosophical Transactions of the Royal Society B: Biological Sciences, 373: 20170434.

Kerley, G.I.H., Kowalczyk, R., and Cromsigt, J.P.G.M., 2012. ‘Conservation implications of the refugee species concept and the European bison: king of the forest or refugee in a marginal habitat?’. Ecography, 35: 519–529.

Pettorelli, N., Barlow, J., Stephens, P.A., Durant, S.M., Connor, B., Schulte to Bühne, H., Sandom, C.J., Wentworth, J., and du Toit, J.T., 2018. ‘Making rewilding fit for policy’. Journal of Applied Ecology, 55: 1114–1125.

Torres, A., Fernández, N., Zu Ermgassen, S., Helmer, W., Revilla, E., Saavedra, D., Perino, A., Mimet, A., Rey-Benayas, J.M., Selva, N., and Schepers, F., et al., 2018. ‘Measuring rewilding progress’. Philosophical Transactions of the Royal Society B, 373: 20170433.

INDEX

A

abiotic conditions 1, 2

aerial photography 1

Africa 1, 2

Africa, southern 1, 2, 3, 4

agoutis 1, 2

agricultural infrastructure 1

agriculture 1, 2, 3, 4, 5

Alaska 1

albedo effect (definition) 1, 2

Amazon River 1, 2

Amazonia 1

America, North 1, 2

America, South 1

American Naturalist, The 1

American Prairie Reserve (APR) 1

Americas, the 1, 2, 3

animals 1, 2, 3, 4, 5, 6

annual grasses 1

Anthropocene Epoch 1, 2

applied research 1

aquatic ecosystems 1, 2

Arctic, the 1, 2, 3, 4, 5

ARK Nature 1, 2

armadillos 1

Asia 1, 2

atmosphere (definition) 1

atomic bombs 1

aurochs (wild cattle) 1, 2, 3, 4

Australasia 1

B

Baerselman, Fred 1

Bakker, Elisabeth S. 1

bat, fruit 1

bears 1, 2

beavers 1, 2, 3, 4, 5

beetles 1

Belarus 1

Bering Strait 1

Beringia 1

Białowieża forest, Poland 1, 2, 3

biodiversity, science of 1, 2

biome (definition) 1

biomes 1, 2, 3, 4

‘biophilia’ hypothesis 1

biosphere 1, 2

biotic conditions 1, 2

birds

extinction 1

farmland 1

food 1, 2

pesticides 1

of prey 1, 2, 3, 4

sourcing 1

species 1, 2, 3, 4, 5

Birnie, Neil 1

bison 1, 2

grazing 1

herds 1, 2

hunted 1

survival 1

trophic layers 1

boar, wild 1, 2

Bond, William 1

bone finds 1

Boorman, John, The Emerald Forest 1

Bothma, Jacobus du P. 1

Brazil 1

Brewster, Rob 1

Brunbjerg, Ane Kirstine, ‘Ecospace: a unified framework …’ 1

buffalo 1, 2

Bulgaria 1

Burrell, Charles 1

bushes 1, 2, 3, 4

C

C4 grasses 1

Cairns, Peter 1

carbon 1

‘bomb’ 1

emissions 1, 2, 3, 4

carbon- 14 dating 1, 2, 3

carcasses 1, 2, 3, 4, 5, 6

carnivores 1, 2, 3

Carroll, Shaun, The Serengeti Rules 1

Carson, Rachel, Silent Spring 1

cartography 1

cats 1

cattle 1

breeds 1, 2, 3, 4

de-domestication 1

digestion 1, 2, 3

herds 1, 2, 3, 4

policy and 1

wild 1, 2, 3

in winter 1

Cerrado biome, Brazil 1, 2

cheetahs 1, 2

Chersky, Russia 1, 2

Church, George 1

Clements, Frederic 1, 2, 3

climate 1, 2

climate change 1

climax vegetation (definition) 1

closed-canopy forest 1, 2, 3, 4

colonialism 1, 2

colonisation 1, 2

Columbus, Christopher 1

conservation biology 1

Conservation Land Trust (CLT) 1

conservation narratives 1

Cornell Lab of Ornithology 1

coyotes 1

Cromsigt, Joris 1

crops 1

Current Biology 1

D

dams 1, 2

Dandy, Norman 1

Darwinian evolutionary theory 1, 2

data, collecting 1

databases 1

de-domestication 1, 2, 3

de-extinction 1, 2, 3

de Kroon, Hans 1

deer

red 1, 2, 3, 4

species 1, 2, 3, 4, 5

deforestation 1, 2

delta landscapes (polders) 1

depopulation 1, 2, 3

design, rewilding by 1

diclofenac, use of 1

digestion 1, 2, 3

discovery, age of 1

diseases, livestock 1, 2

dispersal 1, 2, 3

DNA, ancient 1, 2, 3, 4

dodo 1

Donlan, Josh, ‘Pleistocene Rewilding: …’ 1, 2

Doughty, Chris 1, 2, 3, 4

drainage infrastructure 1, 2

dung 1, 2, 3, 4, 5, 6, 7

Durrell, Gerald, Golden Bats and Pink Pigeons 1

dykes (banks) 1, 2, 3, 4

E

eagles 1

Earth Day (1970) 1

earth system science 1

ecological connectivity (definition) 1

ecological restoration, rewilding vs. 1

ecospace (micro-habitat) 1, 2, 3, 4

ecosystem processes, rewilding 1

ecosystem recovery 1

eDNA (definition) 1

eggs, turtle 1

Ejrnaes, Rasmus, ‘Ecospace: a unified framework …’ 1

elephants 1, 2, 3, 4, 5, 6

elk 1, 2, 3

Elton, Charles 1, 2

emergent property (definition) 1

endangered species 1, 2, 3

Endangered Species Act (1973) 1

England 1

environmental movement 1

environmental narrative, rewilding as 1

environmentalism 1, 2, 3, 4, 5, 6

Eocene Epoch 1

EU nature directives 1

eugenics 1

Europe 1, 2, 3, 4, 5, 6

European Rewilding Network 1, 2

European Wildlife Bank (EWB) 1, 2

extinction

birds 1

de-extinction 1, 2, 3

Holocene 1, 2

island 1

megafauna 1, 2, 3

‘sixth extinction crisis’ 1

wildlife 1

extreme rewilding 1

F

Fairfield Osborn, Henry, Our Plundered Planet 1

farmers, rewilding and 1

fear, landscape of 1

fencing 1, 2, 3

fermentation 1

fertiliser 1

field sizes 1

Finite Earth narrative 1, 2

fire 1, 2, 3, 4

fish 1, 2, 3, 4, 5

fisheries science (definition) 1

flooding 1, 2

floodplains 1, 2, 3, 4

food chains 1, 2

Foreman, Dave 1, 2, 3

forest (definition) 1

Forest Policy and Economics 1

forestry 1

forests 1, 2, 3, 4, 5

fossil soils 1

foxes, red 1

‘framing’ 1

free-market economy 1

Freese, Curt 1

freshwater biodiversity 1, 2

frugivore (fruit-eater) 1

fruit 1

functional species 1, 2

functionalism 1, 2

fundamental (basic) research 1

fungi 1, 2

G

Galetti, Mauro

‘The Forgotten Megafauna’ 1

‘Why are we protecting […] Holocene extinctions?’ 1, 2

game animals 1, 2

geese 1

Gelderse Poort scheme 1, 2

geosphere (definition) 1

geothermal heat 1

Gerrity, Sean 1

glades 1

Global Boundary Stratotype Section and Point (GSSP) marker 1

global nutrient transport 1

global warming, human-induced 1

globalisation 1

goats 1, 2

Goderie, Ronald 1

Goffman, Erving 1

gomphotheres (elephant relative) 1, 2, 3, 4

government action 1

GPS devices 1

gradients, natural world 1

grasses 1, 2, 3, 4

grasslands 1, 2

gravel banks 1

grazers 1, 2, 3, 4, 5, 6, 7, 8

grazing

grassland 1, 2

island 1, 2

loss of 1

moose 1

rough 1

wood-pasture 1

Greater Yellowstone Ecosystem 1

‘green world’ hypothesis 1

Greene, Joshua, Moral Tribes 1, 2

guilds see herbivore guilds

H

Hairston, Nelson 1

Hansen, Dennis, ‘The Forgotten Megafauna’ 1

hay 1

Helmer, Wouter 1, 2

herbivore guilds 1, 2, 3, 4, 5

definition 1

herbivores 1, 2, 3

ecospace and 1

large 1, 2, 3

numbers 1, 2, 3

herbs 1

herds

bison 1

cattle 1, 2, 3

horses 1, 2

hippos 1

Holocene Epoch 1, 2, 3

horses 1, 2

breeds 1, 2, 3, 4, 5

herds 1, 2

migration 1

teeth 1, 2

wild 1, 2

Hudson River 1

humanities 1

hunters, commercial 1

hunting, human 1, 2

hunting, trophy- 1

hydropower dams 1

hydrosphere (definition) 1

hyenas 1

hypsodonts 1

I

Iberá project, Argentina 1, 2

Île aux Aigrettes, Mauritius 1

imperialism 1

indigenous people 1, 2

Indonesia 1

inductive scientific method (definition) 1

industrial revolution 1

industrialisation 1

infrastructure 1

infrastructure, engineering 1

insect biomass, flying 1

insects 1, 2, 3, 4, 5, 6, 7

Integrative Biodiversity Research (iDiv) 1

International Union for Conservation of Nature (IUCN) 1, 2

investing, in rewilding 1

ions (definition) 1

irrigation channels 1

island biogeography theory 1, 2

island rewilding 1

J

Janzen, Dan 1, 2

Jepson, Paul, ‘Recoverable Earth’ 1

Jiménez-Pérez, Ignacio 1

K

Kahneman, Daniel, Thinking, Fast and Slow 1

Kerley, Graham 1

keystone species (definition) 1

Knepp Wildland project 1, 2

Kowalczyk, Rafał 1

Kruger National Park 1

L

lakes 1

land abandonment 1, 2, 3

landscapes

delta (polders) 1

European pastoral 1, 2

wood-pasture 1, 2, 3, 4

‘Landscapes of Fear’, paper 1

Laundré, John, ‘Landscapes of Fear: …’ 1

Leopold, Aldo 1

Lewis, Meriwether 1

Libby, Willard 1

lions 1

livestock 1, 2, 3, 4

Living Planet Index 1

‘Living Rivers’ campaign 1

lizards 1

M

MacArthur, Robert 1

Macias-Fauria, Marc 1

mainstream, rewilding becoming 1

Malhi, Yadvinder 1, 2, 3

mammals 1, 2, 3, 4, 5, 6, 7, 8

mammoths 1, 2, 3, 4, 5

Mandela, Nelson 1

marine environment 1, 2, 3, 4

marine fauna 1

marine systems 1

Martin, Paul, Twilight of the Mammoths: … 1, 2, 3, 4

Mauritian Wildlife Foundation (MWF) 1

Mauritius 1, 2

mega-herbivores 1, 2, 3, 4, 5, 6, 7

megafauna 1, 2

bone finds 1

defining 1

downgrading 1

extinctions 1, 2, 3

and Pleistocene Park 1

Mekong River 1

meso-predators (mid-sized) 1

methane emissions 1

micro-habitat (ecospace) 1, 2, 3

micro-organisms 1, 2

Middle Ages 1, 2

Middle East 1

migration 1

models, rewilding 1

Monbiot, George, Feral: Searching for Enchantment … 1

monitoring rewilding 1

Montana 1

moral world views, bridging 1

musk ox 1

N

narrative interplays 1

natural baselines (definition) 1

natural disturbances 1, 2

nature

-based solutions 1

development 1

and modern society 1

Nature Geoscience 1

Netherlands 1, 2, 3, 4, 5, 6, 7, 8

New Forest 1

Newton, Adrian 1

Nijmegen, Netherlands 1, 2

nitrogen 1, 2, 3

Nogues-Bravo, David 1

Noss, Reed 1

novel ecosystems 1

nutrient cycling 1

nutrient transport, global 1

O

omnivores 1

Oostvaardersplassen (OVP), Netherlands 1, 2, 3, 4

organisational form, of rewilding 1

organisms, dispersal of 1

otters 1, 2

‘overchill’ hypothesis 1, 2, 3

‘overkill’ hypothesis 1, 2, 3

P

Pacific Salmon Restoration Programme, US 1

paddy fields 1

Paleocene Epoch 1

palm oil 1

palms, tropical 1

parks, rewilding 1

passive rewilding (definition) 1

peatland 1, 2, 3

peccaries 1, 2

perennial grasses 1

permafrost (yedoma) 1, 2, 3, 4

pesticides 1

Pettorelli, Nathalie 1

phosphorus 1, 2

photosynthesis (definition) 1, 2

phylogenomic analysis 1

phytoliths (silica particles) 1, 2, 3, 4

phytoplankton 1, 2

pigs 1

plants

aquatic 1

flowering 1, 2, 3

growth 1

native 1

wetland 1

woody 1

Pleistocene Epoch 1, 2, 3, 4, 5

‘Pleistocene Park: return of the mammoth’s ecosystem’ (Zimov) 1

Pleistocene Park, Siberia 1, 2, 3

‘Pleistocene Rewilding: an optimistic agenda …’ (Donlan et al) 1

Pleistocene rewilding (definition) 1

policy, adapting 1

politics and policy 1, 2, 3, 4

pollen 1

pollen dating 1, 2

ponies 1

ponies, Konik 1, 2

port towns 1

prairies 1, 2

precipitation 1

predators

carcasses and 1

food chain 1

and herbivores 1, 2

landscape of fear 1

removal 1

return of 1, 2, 3

species 1

Proboscideans (mammals with trunks)

elephants 1, 2, 3, 4, 5, 6

mammoths 1, 2, 3, 4, 5

Proceedings of the Royal Society 1

programmes, science 1

progress, rewilding 1

‘protectionist’ world view 1

Pucek, Zdzisław 1

puma 1

R

rabbits 1, 2

radioactivity 1

rainforests, tropical 1, 2

ranchers, and rewilding 1, 2, 3

random disturbances 1

rats 1

reasoning, deductive 1

Recoverable Earth narrative 1

refaunation (definition) 1

Reich, David, Who We Are and How We Got Here 1

replacement species (definition) 1

rewilding (definition) 1

Rewilding Europe 1

Rewilding Iberia 1

rewilding narrative 1, 2, 3

Rhine, River 1

rhinos 1, 2, 3, 4, 5

rinderpest (disease) 1

Rio Earth Summit (1992) 1

river systems 1, 2, 3, 4, 5, 6, 7

rock layers 1

rodents 1, 2

Romania 1, 2

roofs, green 1

Round Island, Mauritius 1

Russia 1

S

salmon 1

Sandom, Chris 1

saplings 1

satellite imagery 1

savannas 1, 2, 3, 4

scavengers 1, 2, 3

Schepers, Frans 1

Science 1, 2

Scotland 1

Scotland: the Big Picture (StBP) 1

seeds

dispersal of 1, 2, 3, 4

grass 1

plant 1

tree 1, 2, 3

self-willed nature 1

settlements, human 1, 2, 3, 4

Seychelles 1

Shapiro, Beth, How to Clone a Mammoth 1

sheep 1, 2, 3, 4

shifting baselines 1

Siberia 1, 2, 3

‘sixth extinction crisis’ 1

Slobodkin, Lawrence B. 1

sloths 1, 2, 3

Smart Cities 1

Smith, Frederick E. 1

snow 1, 2, 3, 4

social sciences 1

soil

carbon in 1

fertility 1

fossil 1

layers 1

nutrients 1, 2, 3

peatland 1, 2, 3

permafrost (yedoma) 1, 2, 3, 4

pH 1

Soulé, Michael 1

Southwood, Richard 1, 2

soya 1

spaces of innovation (definition) 1

species pools 1

spiders 1

steppe grasslands 1, 2, 3, 4

Sun, the 1

surprises, nature 1

Survival International 1

‘sustainable use’ worldview 1

Svenning, Jens-Christian, ‘Science for a wilder Anthropocene: …’ 1, 2

systems, thinking 1

T

taiga (boreal forest) 1

Tamaraw Conservation Programme (TCP) 1

tarpan (horse) 1, 2

Tauros Foundation (TF) 1, 2, 3

taxon substitution (definition) 1, 2, 3

technology, growth of 1, 2, 3

teeth, fossil 1, 2, 3, 4

temperature 1, 2

Terborgh, John 1

3Cs 1

Tompkins, Douglas and Kristine 1

topography 1, 2

tortoises 1, 2, 3

tourism 1

traders 1, 2

translocation rewilding (definition) 1

transport systems 1

Tree, Isabella, Wilding 1, 2, 3

trees 1, 2

carbon in 1

fast-growing 1

seeds 1, 2, 3

species 1, 2, 3, 4

trophic cascade theory 1

trophic complexity 1

trophic controls, top-down (definition) 1

trophic rewilding (definition) 1

tropical rainforests 1

tundra 1

turtles 1

Tversky, Amos 1

21st-century rewilding 1

U

Ukraine 1

United States (US) 1, 2, 3

urban populations 1

urban rewilding 1

US Fish and Wildlife Service (USFW) 1

V

vegetation, ‘climax’ 1, 2

vegetation turnover, cyclic 1, 2

Vera, Frans, Grazing Ecology and Forest History 1, 2, 3, 4

vermin 1, 2, 3

vertebrates 1, 2

Vogt, William, The Road to Survival 1

W

Waal, River 1

Wales 1

weeds, invasive 1

welfare, animal 1, 2, 3, 4

well-being, human 1

wetlands 1, 2

whales 1, 2

wheat 1, 2

Widstrand, Staffan 1

wildfowl 1

wildlife protection 1

William the Conqueror 1

Willis, Kathy 1

Wilson, Edward O. 1, 2

windmills 1

‘windscreen phenomenon’ 1

wolves 1, 2, 3, 4, 5, 6, 7

wood-pasture landscape 1, 2, 3, 4

wood, use of 1

World Wide Fund for Nature (WWF) 1, 2, 3, 4

worms 1

Wynne-Jones, Sophie 1

Y

Yamnaya (herding culture) 1

yedoma (permafrost) 1, 2, 3, 4

Yellowstone national park 1, 2, 3

Yukon 1

Z

Zamboni, Talía 1

Zimov, Nikita 1, 2, 3, 4

Zimov, Sergey, ‘Pleistocene Park: …’ 1, 2, 3, 4

COPYRIGHT

Published in the UK and USA in 2020
by Icon Books Ltd, Omnibus Business Centre,
39–41 North Road, London N7 9DP
email: info@iconbooks.com
www.iconbooks.com

Sold in the UK, Europe and Asia
by Faber & Faber Ltd, Bloomsbury House,
74–77 Great Russell Street,
London WC1B 3DA or their agents

Distributed in the UK, Europe and Asia
by Grantham Book Services,
Trent Road, Grantham NG31 7XQ

Distributed in the USA
by Publishers Group West,
1700 Fourth Street, Berkeley, CA 94710

Distributed in Australia and New Zealand
by Allen & Unwin Pty Ltd,
PO Box 8500, 83 Alexander Street,
Crows Nest, NSW 2065

Distributed in South Africa
by Jonathan Ball, Office B4, The District,
41 Sir Lowry Road, Woodstock 7925

Distributed in India by Penguin Books India,
7th Floor, Infinity Tower – C, DLF Cyber City,
Gurgaon 122002, Haryana

Distributed in Canada by Publishers Group Canada,
76 Stafford Street, Unit 300
Toronto, Ontario M6J 2S1

ISBN: 978–178578–627–3
eISBN: 978–178578–628–0

Text copyright © 2020 Icon Books Ltd

The authors have asserted their moral rights.

No part of this book may be reproduced in any form, or by any
means, without prior permission in writing from the publisher.

Typeset in Iowan by Marie Doherty

Printed and bound in Great Britain
by Clays Ltd, Elcograf S.p.A.