Trophic rewilding uses species (re)introductions to restore trophic interactions and complexity, to promote resilient, biodiverse, self-regulating and self-sustaining ecosystems. Typically, this involves top-down and associated trophic cascades where a top consumer/predator controls the primary consumer population [
59,
60]. Hence, if successful, this would reverse defaunation by re-introducing missing wildlife and halt biodiversity declines. Ecosystem engineers are “organisms that demonstrably modify the structure of their habitats” [
61], and, in rewilding, may include beaver, elephants, bison, elk, cattle (as analogues for the now extinct aurochs) and pigs (as equivalents for wild boar). They may also be keystone species, which are those with a disproportionately large environmental effect compared to their abundance, for example beavers. The presence of keystone species (e.g., predators, pollinators, and herbivores) can help to build biodiversity and food webs, while ecosystem engineers can aid in the physical development of landscapes (e.g., river meanders and wetlands), and by creating or maintaining habitats that benefit other species. As they perform their own particular ecological functions, large mammals can also effect changes in biogeochemical pathways in ecosystems [
59,
60].
Apex predators may be required in some rewilding projects to prevent browsing and grazing animals from over-breeding (and hence over-feeding), and exceeding the ecological carrying capacity of the rewilding area. Nonetheless, while predators are important agents in ecosystems, it is not always clear whether their control of prey populations is from direct predation or a less direct mechanism, for example, Behaviourally Motivated Trophic Cascades [
62], also termed the “Ecology of Fear” [
63]. For example, it is generally believed that the reintroduction of wolves in Yellowstone caused changes in elk grazing patterns, which allowed aspen forests and other vegetation to regenerate. However, this has recently been called into question [
64].
The (re)introduction of animals is often done on a case by case basis [
65]. So, while large landscapes (e.g., in Eastern Turkey) can have wolves, bears, lynx,
etc. introduced [
66], this is probably not viable for smaller, urban regions [
67]. In the UK, the Dangerous Wild Animals Act 1976 restricts the reintroduction of certain animals, including bison, wild boar and lynx, while the Wildlife and Countryside Act 1981 sets out the licensing, consultation and assessment requirements for native species which may be legally reintroduced [
68]. Various aspects of Trophic Rewilding have been surveyed in articles collected in a special issue of Philosophical Transactions of the Royal Society B [
69].
Human-Wildlife Conflict
As already noted, the fear exists that, once introduced, dangerous animals might make their way into towns and cities [
1], and the reintroduction of brown bears to Italy’s Trentino province, through the EU-funded Life Ursus project, has led to growing tensions between humans and wildlife. Initially, the scheme was applauded, but now that there are more than 100 bears, conflicts with humans have increased in number, including the fatal attack on Andrea Papi in 2023, which is the first modern death from a wild bear in Italy [
70]. While calls for stricter controls have been elicited, including the culling of dangerous bears, others argue that such conflicts are a result of poor management, inadequate public education, and a lack of preventive measures such as bear-proof bins [
70]. Farmers have also opposed plans to reintroduce the lynx in the United Kingdom because of fears that this will lead to an increase in sheep predation. However, others maintain that lynx preferentially prey on foxes, which attack sheep, so introducing them may prove beneficial [
71].
It is sometimes debated whether humans are the top apex predator [
72], although, a study of the human trophic level (HTL) may be noted, which concluded that, in the context of the global food web, the answer is no, and that humans are similar to anchovies or pigs [
73]. Nonetheless, for example, on the Knepp Estate, a 3500-acre rewilding project, it is humans that kill cattle, pigs,
etc., partly from its business activities but mainly to keep numbers in check, so in a rewilding area without bears, wolves, lynx,
etc., humans may function as a surrogate apex predator [
74].
The ecological benefits of trophic rewilding have been evaluated empirically by means of a 9-year exclosure experiment [
75], which concludes that trade-offs exist between rewilding strategies, in regard to biodiversity and ecosystem function. Thus, woody plant diversity and total carbon storage were reduced by 73% and 23%, respectively, compared to passive rewilding plots that excluded mammalian herbivores. In contrast, plant diversity and carbon storage were improved compared to land where agriculture had continued, e.g., artificial pastures associated with intensive livestock production. The diversity and biomass of ground-dwelling arthropods were enhanced by 21% and 167%, respectively, relative to passive rewilding, partly because more structurally complex vegetation was created by trophic rewilding. Overall, it is concluded that tropic rewilding is not a panacea for conserving biodiversity and ecosystem functions, and how it should be used in restoration depends on those particular conservation outcomes that a society places value upon [
75].
Svenning et al. have stressed that, from what is currently known, the evidence is that trophic cascades may be successfully restored via species reintroductions and ecological replacements. Nonetheless, the influence of megafauna is subject to various factors that are, as yet, not well understood. It is proposed that applied programmes be implemented to assess the role of trophic complexity, interplay with landscape settings, land use, and climate change, as well as determining scope for rewilding globally, and means to maximize benefits and mitigate human–wildlife conflicts [
59].
The complexity of tropic rewilding is highlighted elsewhere, from which it is concluded that a range of social and ecological context dependencies can cause outcomes in a rewilded carbon cycle to vary, and lead to ethical considerations for successful implementation. Those technologies that are currently available for predicting and monitoring progress toward both biodiversity and climate mitigation goals have also been surveyed [
76].
8. Rewilding to Ameliorate the Climate Emergency and Biodiversity Crisis
The world is experiencing a climate emergency and biodiversity crisis [
11,
77], among which is the catastrophic decline in insect numbers, which is of particular concern [
78,
79]. However, rewilding strategies offer the potential to both ameliorate and provide resilience to climate change, supporting biodiversity in the process [
80], as a result of carbon capture and storage, changes to the Earth’s albedo, natural flood management, reduction of wildfire risk, and facilitating species to move to new, climate safe habitats, thus creating biodiverse and climate resilient ecosystems. Some of these aspects are considered below. Through its diversification of the range of outcomes provided, rewilding may offer a supporting approach to natural climate solutions, ensuring the delivery of other nature-based benefits to biodiversity conservation and society [
81].
8.1. Herbivores and Carbon
When herbivores consume vegetation, carbon is assimilated within their biomass and released by respiration, digestion and defecation [
82]; hence, the rewilding of
large herbivores is the most significant in terms of biogeochemical cycling and the development of ecosystem structure [
83]. For example, in a tropical forest in Guyana it was found that, when numbers of mammalian species were increased from 5 to 35, tree and soil carbon storage rose by a factor of four to five, respectively, as compared with an increase of 3.5 to four times by increasing the number of tree species from 10 to 70 [
84]. Large herbivores can influence climate change in a number of ways, both direct and indirect [
85]. For example, reindeer (
Rangifer tarandus) and muskoxen (
Ovibos moschatus) are the only large herbivores in the Arctic, where temperatures are increasing, and so thermophilic plant species are invading the tundra. The reindeer and muskoxen are able to maintain the composition of vegetation there, even in a warmer climate [
86], and also prevent the expansion of woody plants as temperatures rise, thus maintaining a greater albedo [
87] and consequent cooling effect. While uncertainties remain, it seems probable that the introduction of increased numbers and diversity of large herbivores may mitigate some of the consequences of warming in the Arctic [
85]. Thus, we may note “Pleistocene Park”, a future-oriented rewilding project set in Arctic Siberia to slow the melting of permafrost, by introducing large herbivores into the area [
88].
The loss of fauna from tropical rainforests leads to a reduction in the dispersal of tree species with megafaunal fruits, which have a higher wood density and contribute strongly to carbon storage in tropical forests [
89]. Accordingly, the introduction of large herbivores could enhance the forest’s carbon storage potential [
85]. By replacing ruminant livestock with non-ruminant wildlife on rangelands, a significant reduction in greenhouse gas emissions could be achieved [
85]. It has been proposed by Cromsigt et al. [
85] that populations of large (>100 kg) non-ruminant herbivores should be the focus of tropic rewilding as a climate mitigation approach.
8.2. Natural Climate Solutions and Rewilding
A comprehensive analysis was made of twenty natural climate solutions (NCS), involving conservation, restoration, and/or improved land management actions that might be adopted to increase carbon sequestration and/or to curb emissions of greenhouse gases globally, across forests, wetlands, grasslands, and agricultural lands. It was deduced that one-third of the climate mitigation needed up to 2030 as required to keep global heating below 2 °C could be provided by such NCS methods [
90]. More recently, Schmizt et al. have argued that NCS typically underrate the importance of animals in controlling the carbon cycle, and present evidence that by protecting and restoring key wild animals and their functional ecosystem roles, natural ecosystem carbon sinks can be “supercharged”. The paper shows that an additional 0.6 Gt CO
2 per year could be sequestered by restoring populations of just 3 species: baleen whales, bison and African forest elephants. Furthermore, the authors emphasise the critical role of marine and other key species in the global carbon cycle, which could absorb another 5.8 Gt CO
2 per year [
91].
In their Rewilding and Climate Breakdown report [
92], Rewilding Britain has estimated that by restoring and protecting native woodlands, peatlands, heaths and species-rich grasslands over 30% of the UK landscape (7 million hectares), 53 million tonnes of carbon dioxide could be sequestered per year, which is over 12% of current UK emissions. Similarly, Rewilding Europe have estimated that by rewilding over 10% of European land, 10% of European emissions could be captured and stored, and that this could be done at a “cost per sequestered tonne of carbon” of around 25–50 euros, which is far cheaper than most other carbon sequestration methods [
93]. In its 7th Carbon Budget, the UK Climate Change Committee have offered several land-based mitigation options: improved management of existing forests and woodland generation, perennial energy crops, restoration of degraded peatlands, sustainable agriculture on organic soil, along with an expansion of agroforestry and hedgerows. Under the Balanced Pathway, these measures are predicted to bring about emissions savings for the UK of around 8 Mt CO
2e in 2040, rapidly increasing to around 25 MtCO
2e in 2050 [
94].
Due to deforestation, Mo et al. have estimated that the total carbon stored in global forests is 328 billion tonnes below their optimum, natural capacity. However, they conclude that, without encroaching on urban or agricultural lands, forests could capture a total of around 226 billion tonnes of carbon: 61% of this (139 Gt C) by protecting existing forests (“proforestation”), so that they can recover to maturity, and the remaining 39% (87 Gt C) through reconnecting fragmented forest landscapes using restoration and sustainable ecosystem management [
95]. The integration of rewilding with forest management has been emphasised to improve trophic complexity, natural disturbances, and species dispersal, thus enhancing biodiversity, resilient carbon storage, and social-ecological resilience [
96].
Tropical rainforests appear to be particularly susceptible to, and hard hit by, the effects of climate change, and the Brazilian Amazon is found to have emitted a net 3.6 Gt CO
2 (equivalent) over the past 20 years. Based on satellite monitoring data, it is concluded that the best chance for preserving the Amazon, and its ability to buffer against climate change, lies in placing formally protected areas and lands in the care of indigenous peoples [
97]. Elsewhere, it has been proposed that, to preserve global biodiversity and rewild key habitats, science and Indigenous knowledge must work in partnership, while also being restitutive and rights based. Such traditional and Indigenous knowledge has successfully preserved and restored biodiversity across the globe, although its validity compared with Western science is far less well recognised [
98].
8.3. Wetlands
Worldwide, the remaining area near natural peatland (over 3 million km
2) sequesters 0.37 gigatonnes of CO
2 a year. Peat soils contain more than 600 gigatonnes of carbon, representing up to 44% of all soil carbon, and exceed the carbon stored in all other vegetation types, including the world’s forests [
99]. However, when drained for agriculture, peatlands transform from a carbon sink to a carbon source, releasing carbon stored over centuries into the atmosphere. Emissions from drained peatlands are estimated at 1.9 Gt of CO
2e annually, equivalent to 5% of global anthropogenic greenhouse gas emissions, and hence their preservation and restoration are critical to ameliorate climate change and biodiversity loss. Indeed, it has been estimated that by ending the conversion and degradation of forests, wetlands and peatlands (restoring them instead), some 9 Gt CO
2 per year could be sequestered by 2050 [
100].
In terms of actual means to begin addressing this, we may note the Global Peatlands Initiative [
101], which was inaugurated at the 2016 UNFCCC COP in Marrakech, Morocco, aiming to preserve peatlands “as the world’s largest terrestrial organic carbon stock and to prevent it from being emitted into the atmosphere”. Rewilding Britain has outlined the broader issue of restoring wetlands, in their many different forms [
102], and Rewilding Earth have provided a concise guide to accomplishing this [
103].
To mark World Wetlands Day (2 February 2025), the Global Rewilding Alliance, along with ten partner organisations, launched a report, “Taking Animals into Account”, which, based on 11 case studies, demonstrates the vital role played by wild animals in keeping the world’s wetlands functional and resilient
. Evidence is presented that the reintroduction and protection of key wild animal species could be a “game changer” in regard to addressing climate change, biodiversity loss, invasive species control, and water security challenges [
104].
Harvey and Henshaw have examined rewilding in the context of the hydrological changes it might deliver, through reducing land management, natural vegetation regeneration, species (re)introductions, and changes to river networks. This involves major changes to above- and below-ground vegetation structure (and hence interception, evapotranspiration, infiltration, and hydraulic roughness), soil hydrological properties, and the biophysical structure of river channels [
105]. Harvey et al. have investigated this further, in terms of using rewilding to mitigate hydrological extremes, e.g., floods and droughts, and offer aims for future research: capture effects on both high and low flow extremes for a given type of change; to analyze both magnitude and timing characteristics of flow extremes; and examine temporal trajectories (before and after data), ideally using a full before-after-control-impact design [
106].
Rewilding Europe has showcased a number of projects involving the rewilding of rivers across Europe and the areas around them. By creating healthy, free-flowing rivers that are well-connected with the surrounding landscapes, a wide range of habitats for wildlife species are developed, including enlarged grazing areas, and allowing the river to perform its natural function as a buffer. Such “waterscapes” help to purify water and lessen flooding downstream during periods of heavy rainfall; they are also more resilient to the effects of climate change [
107].
Rights of Nature (RoN) refers to a legal framework which aims to promote and assert natural rights and move towards a system where nature is valued and protected for its own sake and not for the value it provides to humans. Kings College London has offered the following, fuller definition: “RoN prioritises the intrinsic rights of nature and the undeniable inter-connection between the human and natural world. RoN rejects a “human-centric” (or anthropocentric) approach in which law treats nature as property and conceptualises the world in terms of property rights. Instead, the RoN movement aims to promote and assert natural rights and move towards a system where nature is valued and protected for its own sake, not for the value it provides to humans. In other legal systems, such as those of indigenous persons, the RoN approach is used to protect natural entities such as rivers and forests, and around the globe, new laws and constitutions which recognise RoN are gradually being introduced. Alongside this shift, RoN lawyers and activists are also re-imagining existing laws through a RoN lens.” To assist with the latter efforts, the college has produced a “legal toolkit” for the protection of rivers in England and Wales [
108].
8.4. Wildfires
Although the frequency and intensity of fires have multifold effects on climate, their net effect remains uncertain [
85]. Nonetheless, fires are significant sources of greenhouse gas emissions, and their smoke can alter the Earth’s albedo (ability to reflect sunlight into outer space). Wildfires may be increasing in areas more prone to droughts due to climate change [
109], the incidence of which can be reduced using trophic rewilding. Since they consume large amounts of potential fuel, large grazers are the most effective. Grazing and browsing are thought to reduce the risk of wildfires: for example, the loss of wildebeest from the Serengeti led to an increase in grass, due to lack of grazing, which led to more frequent and intense fires, and caused the grassland to convert from a carbon sink to a carbon source. When the wildebeest population was restored through disease management practices, the Serengeti became a carbon sink once more [
91].
A new study shows that holistic landscape management, with rewilding playing a key role, may be effective in preventing large wildfires (>1 km
2) in Mediterranean regions [
110]. Along with other parts of the world, the UK has seen record outbreaks of wildfires in recent years. However, there is increasing evidence that healthier, more diverse ecosystems—including those with a variety of vegetation, wetland habitats, key species of wildlife, and healthy water-retaining soils—are more resilient against extreme weather events, including wildfires [
111].
9. Rewilding Landscapes at Scale
It has been argued [
112] that, “
The pursuit of wilderness has been abandoned in favor of wildness, vindicated by the so-called ‘rewilding philosophy’. Rewilding does not pursue wilderness, no longer possible in the hybrid Anthropocene, but aims to restore the spontaneous order of the wildness”. Thus, as we have seen, humans are essential agents in the rewilded landscape.
Winning the Earthshot Prize in 2024, the Altyn Dala Conservation Initiative is working to restore Kazakhstan’s steppe ecosystem. It has successfully brought the endangered Saiga antelope back from the brink of extinction. It is one of the largest rewilding projects in the world, covering an area of over 75 million hectares, roughly the size of Turkey [
113]. An inverse relationship has been demonstrated between the degree of management intensity and size of the rewilding landscape, described as becoming “bigger, better, more joined up” as the landscape scale increases [
6].
A conceptual framework—Spatial Planning of Rewilding Effort (Spore)—has been devised for the spatial optimisation of ecological function. This can improve the ecological outcome of rewilding by maximizing overlap between where the function is provided and where it is needed. It is proposed that Spore can be used to identify priority areas and produce relevant maps, thus actively engaging stakeholders in a collaborative effort to construct effective rewilding projects [
114]. Dedicated to the late and esteemed Professor Dame Georgina Mace, and published by The Royal Society of London, is a policy document aimed to assess the best management of multifunctional landscapes, by means of an overarching decision-making framework within which potentially competing commitments can be reconciled against one another [
115].
Elsewhere, Perino et al. have offered a framework intended to guide researchers and managers in choosing rewilding actions. It applies to various rewilding approaches, ranging from passive to trophic rewilding, and aims to promote beneficial interactions between society and nature [
5]. In this paper, the authors further propose that Rewilding can be broken down into 3 dimensions (“The 3 D’s of Rewilding”), all of which build back stability: Diversity, Disturbance, and Dispersal.
The expansion of European protected areas through rewilding is addressed by Araujo and Alagador, who conclude that around 117 million hectares is suitable for rewilding, 70% of which is in cooler climates. They show that opportunities for passive rewilding are predominant in Scandinavia, Scotland, and Iberia, with active rewilding prospects being widely distributed across Europe. This is an important distinction and a reminder that rewilding is not
synonymous with the reintroduction of wolves or other large carnivores. Similarly, the paper differentiates between rewilding and “land abandonment”, which offers more limited advantages [
116], while Wang et al., show that rewilding abandoned farmland has greater benefits than afforestation [
117].
Rewilding Europe also note [
118] that “
Rewilding can be the best option for land-use in cases of farmland abandonment in Europe and all over the world when the social structure of farming communities has been eroded and low-intensity farming is no longer socially or economically viable.” du Toit and his coworkers have emphasised the differences between rewilding and restoring an ecologically degraded landscape [
42] , along with policy implications of rewilding [
119], while Ockendon et al. have presented the results of a process attempting to identify 100 questions which, if answered, would make a substantial difference to terrestrial and marine landscape restoration in Europe [
120].
The Nature Restoration Regulation is an unprecedented EU law which came into force on 18 August 2024. This requires Member States jointly to restore at least 20% of the EU’s land and sea areas by 2030. In addition, all ecosystems in need of restoration must be restored by 2050. The law sets specific, legally binding targets and obligations for nature restoration in terrestrial, marine, freshwater, and urban ecosystems [
121], and Rewilding Europe has produced a practical guide to support policy makers and other stakeholders involved in drafting and developing the National Restoration Plans (“NRPs”), under this regulation [
58].
The Iberian Highlands Rewilding Landscape has marked a major milestone, adding 850,000 hectares of land to help upscale rewilding efforts across Europe
. It is Rewilding Europe’s tenth landscape [
122], with others identified here [
123]. The Global Rewilding Alliance and OpenForests have officially launched a map of rewilding projects around the world: organizations have contributed stories, photos and videos for projects in 70 countries covering 1 million square kilometers (386,000 square miles), and the alliance’s leaders say more will be added over time [
124].
Assessing Rewilding Progress
Torres et al. have devised a novel approach for monitoring progress in rewilding, based on its particular ecological attributes. This is based on a bi-dimensional framework for assessing the recovery of processes and their natural dynamics through: (i) decreasing human forcing on ecological processes, and (ii) increasing ecological integrity of ecosystems, intended to broaden the scope of rewilding projects, facilitate sound decision-making, and connect the science and practice of rewilding [
125]. Other workers have devised a “Site Rewilding Potential Score”, which can identify and quantify areas with rewilding potential at a national scale [
126].
The need for an evidence-led approach has been stressed to obtain better spatial planning for future rewilding. This would lead to a map of “appropriate” rewilding areas, based on landscape scale characteristics, national species and habitat priorities, and predicted future landscape changes. Importantly, these ‘target’ areas would also be sensitive to local social, economic and agricultural contexts [
127]. A pioneering method for evaluating rewilding progress has been applied across seven of Rewilding Europe’s operational areas. Positive impacts have been revealed at the site-level, but challenges to upscaling have also been identified [
128].
10. Rewilding and Food Security
In a report by the WWF [
129], it is posited that rewilding advocates have often not engaged appropriately with farmers and are perceived as “elite” outsiders who do not comprehend rural communities or environments. Media coverage has further driven this division, with the result that rewilding and farming are frequently regarded as conflicting with one another. The WWF has proposed that, rather than being seen as a simplistic binary choice between farming and rewilding, the latter should be considered as part of a broad spectrum of approaches to help nature recover. This spectrum incorporates different kinds of “nature-friendly” farming and more “traditional” conservation techniques, with rewilding-type approaches sitting more towards one end of the range. Thus, aspects of cost-effectiveness, landscape fragmentation and stakeholder opposition are all part of the integrated discussion [
129].
Some commentators fear that leaving land to regenerate for nature will compromise food production in the UK and relocate our environmental footprint to other countries. Sustainable food production in the UK needs properly functioning nature—healthy soils, clean and plentiful water, and thriving insect populations, all of which are the foundation of successful farming. In 2021, the UK Government’s Food Security Report [
130] determined climate change and ecological breakdown to be the major challenges to food security. The report concludes that a more effective overall use of land is needed, including diets based more on plants and less on meat, along with reducing food waste [
131].
Similarly, the Dimbleby Report (“National Food Strategy”) concludes that [
132], “
If we were to... increase productivity by 30% and reduce meat eating by 35%, we could produce the same amount of food from 40% less land. Both these scenarios free up enough land not just to achieve our climate goals but also to make space for nature, both in wilder areas and on our farms, without compromising our levels of food self-sufficiency”.
While record temperatures have been experienced during the past few years, it is predicted by the UK Met Office that, as compared to the UK’s climate in 1990, by 2070, winters will be between 1 and 4.5 °C warmer, and up to 30% wetter. Summers will be between 1 and 6 °C warmer, and up to 60% drier, depending on the region, with hot summer days being between 4 and 7 °C warmer. This is likely to have significant effects on health and food production, and some crops may not fare well under hotter and dryer conditions, while excessive rainfall/flooding of fields is a further issue [
133].
From an analysis of the impacts of climate change-driven abiotic stresses on crop productivity, Razzaq et al. have concluded that the overall loss in crop production may exceed US$170 billion year
–1, and seriously endanger global food security. It is argued that wild progenitors of modern crops had a greater stress tolerance, and that our overall paradigm of crop breeding needs to be changed, with a broader use of wild relatives as a major tool in improving resilience to climate change [
134]. In a separate study, Hawkesford has emphasised the use of
de novo domestication of under-utilized crops, wild relatives of crops, and ancestral germplasm, as a means to develop (climate change-) resistant and high-yielding new crops and varieties [
135].
The implications of rewilding for agriculture are examined in a broader context by Fraanje and Garnett. They conclude that, where a large-scale implementation of rewilding occurs, the development of rural landscapes would be influenced significantly, but how exactly nature, agriculture and rural populations would be affected differs according to the particular major rewilding strategy employed in a given region [
136].
Corson et al. propose that agricultural rewilding may provide a multifunctional approach for enabling livestock systems to respond to societal demands more effectively. They conclude that this potential to conserve and restore biodiversity should be explored, along with the benefits delivered to farmers by different kinds of agricultural rewilding and agroecology [
137]. Gordon et al. have identified potential benefits of including domestic and semi-domestic livestock species in the rewilding portfolio. However, this calls for a re-conceptualisation of the characteristics of rewilding and/or rewilded landscapes, and also that some of the policy and regulation constraints imposed on feral/free-living livestock will need to be lifted [
138].
In opposition to the view that crop production losses are inevitable when land is turned over to rewilding, Pywell et al. have shown that habitat creation in lower yielding areas increased yields in cropped areas of the fields, an effect that became more pronounced over a period of 6 years. It was also found that numbers of birds and insects increased during the process [
139]. The introduction of flower strips and the seminatural habitat surrounding farms was found to increase the numbers of
Diaeretiella rapae, and hence may provide a natural management strategy for the control of
Brevicoryne brassicae densities in brassica crops [
140].
Two practical guides are available, “How to rewild a field” [
141], which stresses that due to human caused distortions of the landscape, just leaving the field to Nature will create a large broadleaf dominated area, rather than the desired natural mix of shrub, grass and woodland; it also mentions the “3 D’s of Rewilding”. The second document addresses the larger-scale challenge, “How to rewild a farm” [
142].
Project Drawdown includes rewilding in the context of NCS aspects [
143], but this is really a call to overhaul the global food system. They note that “the rewilding of agricultural lands could be a big win for climate and nature. But it first requires shrinking the overall footprint of the food system by cutting food waste, shifting away from wasteful diets, and phasing out crop-based biofuels”.
11. Urban Rewilding
Rewilding can also be incorporated into urban environments, where the interconnectivity of smaller spaces over a larger overall city landscape is important, rather than merely isolated pockets of green space, whatever intrinsic value the latter may have. This may include creating habitat corridors with green roofs and walls, improving and extending green spaces, street tree planting, and biophilic design, thus delivering benefits not only to wildlife but also to people, with improvements to their physical and mental health [
144]. It is expected that, by 2050, approximately 70% of the 10 billion expected human global inhabitants are likely to occupy urban areas [
145]. This increase (by 20%) in urban populations will be accompanied by changes in land-cover, with a rapid enlargement of urban footprints and associated with a growth in agricultural land requirements [
146].
Since the most extensive biodiversity losses are occurring in and around cityscapes [
147,
148], these are where actions might be most effectively taken. Initiatives for urban rewilding most likely involve more than the recovery of particular species and community engagement, and may further aim to restore complete historic assemblages of species that have been lost, as is often true with efforts to restore vegetation in city environments.
Notwithstanding the challenges of reintroducing fauna into cities, urban rewilding does offer a unique and, as yet, little explored opportunity to bring the natural environment to city dwellers [
149]. It is thought that biodiversity decline on the global scale is caused by an increasing disconnection between humans and nature, which on the present course, is likely to increase. However, for meaningful community engagement to be part of any urban rewilding effort, the relevant urban green spaces must be safe and accessible, encouraging regular visitation and engagement, as well as being ecologically rich [
149]. Implementing urban rewilding will most likely involve local authority engagement, and means for overcoming potential challenges and maximising opportunities for landscape-scale management have been considered [
150].
As noted on the “How to Rewild” website, which offers a cornucopia of practical information, “Rewilding urban areas isn’t something you do on a site by site basis—it needs to be holistic; taking into account habitats in the wider landscape.” [
151]. ZSL has published a comprehensive report, “Rewilding our Cities”, which concludes that large-scale nature recovery in urban areas could buffer city dwellers against the worsening impacts of climate change (for example, flooding and heatwaves), while also helping to restore biodiversity. The report emphasises that private gardens; green spaces, belonging to councils, businesses and religious groups; and public spaces such as parks, urban waterways, estuaries and wetlands; as well as less obvious areas such as railways, are key locations where rewilding could be implemented at a large enough scale to make a significant difference [
152].
On a more individual and community scale, it has been proposed that “gardens could be joined up to create wildlife corridors, because the biggest problem that many species face is habitat fragmentation. Gardens are generally very small, but if you get together with your neighbours and the people all along your street, then you could really make a contribution.” [
153]. Lehmann has given evidence for the opportunities and benefits of regreening and rewilding cities to strengthen their resilience against climate change, biodiversity loss, and major resource depletion [
154]. Russo et al. have identified that rewilding can have substantial positive social-ecological impacts in urban areas. Thus, as adapted within urban contexts, new solutions may be found for societal challenges such as sustainability and food security. Aspects of concepts, pros and cons, scale, applicability, and particular examples are surveyed [
155].
12. Rewilding in a Changing World
Svenning has proposed that rewilding should be central to the massive restoration efforts necessary to overcome the global biodiversity crisis and enlarge the capacity of the biosphere to mitigate climate change. Critical factors in achieving this include large areas being set aside for nature, the restoration of functional megafauna and other natural factors to promote biodiversity, synergy with major societal dynamics, and judicious socio-ecological implementation [
80]. Thus, rewilding, as adapted systemically, can provide (part of) the solution(s) needed to resolve the systemic problem of the “climate and nature crisis”, also described as being “one indivisible global health emergency.” [
156]. Svenning et al. have further considered introducing megafuana, which may promote vegetation heterogeneity, seed dispersal, nutrient cycling and biotic microhabitats. These are essential drivers of biodiversity and ecosystem function and, under increasingly novel ecological conditions, are likely to become increasingly important for maintaining a biodiverse biosphere [
60]. The broad topic of “Rewilding and restoring nature in a changing world” has been given prominence in papers published in a special issue of PLoS ONE [
157].
Neugarten et al. have determined that, by conserving around half of the global land area, 90% of the ten current contributions to humans from Nature could be achieved, along with minimum representation targets for 26,709 terrestrial vertebrate species. This aligns with recent commitments under the Global Biodiversity Framework to conserve at least 30% of global lands and waters, and proposals to conserve half of the Earth. However, since over one-third of those regions needed to provide Nature’s contributions to humans and other species are also suitable for agriculture, renewable energy, oil and gas production, mining, or urban expansion, future collisions may occur between conservation, climate mitigation and development goals, especially as populations grow [
158].
As a result of human impacts on the environment, unprecedented combinations of organisms are appearing, and while such novel ecosystems would often be thought of as “bad”, from a restoration or conservation viewpoint, there are instances where they can provide benefits such as habitat for plants and animals that are threatened by habitat loss elsewhere. It is possible, then, that such novel ecosystems will need to be reconciled with traditional concepts of restoration/conservation [
159]. It has been proposed that assisted colonisation on a massive scale will likely be necessary, not particularly to conserve threatened species, but to maintain functional forest ecosystems in the United Kingdom. The authors advance that conservationists must shift from largely attempting to prevent species extinctions to maintaining functioning ecosystems to facilitate the emergence of robust novel ecosystems, given the biotic changes that are now inevitable in a hotter world [
160].
The importance of ecological complexity and emergent properties at multiple scales has been highlighted, particularly of individual ecosystems and across landscapes, regarding future restoration efforts. It is proposed that certain current restoration methods might be incorporated within a complexity approach, while also encompassing more novel concepts such as rewilding [
161].
Gardner and Bullock have proposed that, in the climate emergency, conservation must become “Survival Ecology” [
162]. Species and ecosystems are beginning to be subject to unprecedented conditions, which will likely undermine their continuing to exist in historical ranges; nonetheless, conservation remains largely directed towards returning species and ecosystems to a historical state, but where the deleterious impacts of humans are ameliorated. This approach reorients conservation efforts toward a future where humans and other species can coexist within a dynamic planetary system, acknowledging inevitable change, and actively shaping the world’s forward trajectory rather than solely focusing on preserving a static past. They further advance that, since conservation science and advocacy have been insufficient to bring about change on the scale necessary, survival ecologists should also embrace non-violent civil disobedience [
162].
13. Marine Rewilding
The importance of the world’s oceans can hardly be overstated, covering as they do more than two-thirds of the Earth’s surface and representing about 95% of the planet’s biosphere [
163]. They also help to stabilise the climate, by absorbing roughly 30% of anthropogenic (CO
2) emissions [
164] and around 90% of the excess heat reined in by greenhouse gases [
163]. The oceans are also an important source of animal protein for billions of people [
163], and of associated livelihoods in “the blue economy” [
163], along with providing critical wildlife habitat. While more species are assessed to exist on land than in the oceans, this is. Still, one measure of biodiversity, and in contrast, phylogenetic diversity, is reckoned to be higher in the oceans than on land [
165].
Marine and coastal habitats are diverse, ranging from those neighbouring terrestrial environments, for example, estuaries, mangrove forests, coral reefs and seagrass beds; to those in the open ocean, including hydrothermal vents, seamounts and soft sediments on the ocean floor [
166].
The oceans are a major stabilising element of the climate system [
163], but are under threat from heating and acidification. Moreover, new evidence suggests that, with continued warming and CO
2 emissions, the ocean’s capacity to absorb increasing amounts of CO
2 could first stall and then actually reverse [
167]. Further threats are from over-fishing (and unsustainable practices such as bottom trawling), coastal habitat destruction (especially of coral reefs and mangroves) and pollution, for example from river run-off, contaminated with industrial and agricultural waste [
163].
Nonetheless, while terrestrial rewilding has gathered considerable traction and momentum, its marine counterpart is still at a comparatively nascent development stage, although similar overall principles may well apply in both cases [
168]. From a systematic review of the literature, a broad definition of marine rewilding is proposed (given that a growing number of ocean initiatives accord with its general ethos) along with a set of operating principles that can be applied to given regions or cultures, aiming to promote marine rewilding within more established conservation policy and practice [
168]. Cornerier has further examined the concept of marine rewilding with reference to a collection of major marine rewilding initiatives (MRIs) around the world. She emphasises the limitations of technical and scientific tools, the need to bring such rewilding projects into the social and political arenas, and concludes that the implementation of MRIs may spark environmental controversies around the multiple uses of the sea [
169]. Rewilding Britain has given some practical coverage to marine rewilding and its importance, with five representative projects described [
170].
The protection of 30% of the world’s oceans will be a common goal for all those countries party to the “Kunming-Montreal Global Biodiversity Framework” adopted during the 15th meeting of the Conference of the Parties of the Convention on Biodiversity (CBD) in December 2022, over the next decade. Accordingly, a plan to reach the “30 by 30” targets is proposed, based on the distribution of over 150 types of marine species, habitats, ecosystems, and abiotic elements, and the marine protection priority levels of coastal, near-shore, open ocean, and deep ocean trench areas [
171]. To overcome some of the financial barriers for some countries in signing up to the 30×30 agreement, an approach is proposed, based on the context of marine habitats contained by nations’ exclusive economic zones (EEZs), to reduce the costs to all nations [
172].
The most comprehensive assessment has been made, to date, to determine those ocean areas that, if strongly protected, would most contribute to a more abundant supply of healthy seafood and provide a cheap, natural solution to address climate change, in addition to protecting “embattled” species and habitats. It is further concluded that targeting these areas would protect almost 80% of marine species, add over 8 million tonnes of fish to global catches, and prevent the release of more than one billion tonnes of CO
2 by protecting the seafloor from the widespread yet highly destructive fishing practice of bottom trawling [
173]. However, from another study, it is concluded that, to bridge the gap between the current 8% of the global ocean that has some Degree of protection (only 3% being highly protected) and the 30% needed, will require the establishment of another 190,000 small marine protected areas (MPAs) (in coastal regions, alone), and an additional 300 large MPAs (in remote, offshore areas), by the end of 2030 [
174].
14. Rewilding and Human Ecological Overshoot (Aspects of the Broader Canvas)
As we have seen, rewilding can help Nature to regenerate and act to mitigate biodiversity loss and climate change. However, these are but symptoms of the wider underlying issue of human ecological overshoot, as noted by Ripple et al. [
175].
The tendency to focus on carbon emissions, with renewable energy as its antidote, misses much of the broader canvas of threats impinging on nature and society. It has accordingly been termed “Carbon Tunnel Vision” [
176]. Undoubtedly, to rapidly ameliorate increasing atmospheric CO
2 (plus other greenhouse gases) concentrations is essential and critical [
175], since they are causing ocean acidification, elevating air and ocean temperatures, melting of ice sheets, glaciers, and sea ice, rising sea-levels, and are interrelated with biodiversity loss [
11].
In addition [
175], we see collapsing fisheries and coral reefs, deforestation and habitat loss, the draining of fossil aquifers, rivers and lakes, soil erosion, desertification, massive species displacement and extermination, insect die-off, resource depletion, pollution of air, land and water—e.g., by microplastics and “forever chemicals”—all being driven by an unsustainable consumption of 100 billion tonnes of “natural resources” each year, thought to reach up to 184 billion tonnes in 2050 [
177]. Hence, even if we could switch our energy from fossil fuels to “net-zero” emissions, current consumption by human enterprises would continue to exceed and degrade the Earth’s biocapacity. Rees has proposed that, on our present course, a “population correction is inevitable” [
178]. None of those listed above is a single, isolated problem, but components of a complex web of societal and biophysical processes, defined by a set of planetary boundaries, 6 out of 9 now exceeded [
179]. Hence, globally, the overarching collective solution is to reduce current hyperconsumption, for which a set of actions and timescales has been proposed [
77].
The Global Footprint Network [
180] concludes that human enterprises use 1.78 “Earths” worth of resources (2024 data). In other words, we are liquidating “natural capital” 78% faster than the Earth can renew it—treating it as “income”, the dangers of which E.F.Schumacher warned about in his iconic book, “Small is Beautiful”, published in 1973 [
181]. Hence, it is necessary to reduce global consumption by around 44%, although the reductions needed would vary considerably around the world, being greatest in the wealthiest nations (up to 80%). Merz et al. have identified that the root of human ecological overshoot lies in a behavioural crisis, driven mainly by advertising. However, those same mechanisms may also provide means for healing the malady [
12].
Although it is not a “cure” for the condition, the potential of rewilding (as part of an NCS approach) to restore and regenerate ecosystems can play a significant role in addressing ecological overshoot in the following ways:
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Restoring Ecosystem Services: Rewilding can bring back key species, repair damaged ecosystems, and restore natural processes that provide essential services like clean air and water, flood and fire prevention, soil health, pollination and carbon sequestration.
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Increasing Biodiversity: By reintroducing native species and allowing natural processes to shape ecosystems, rewilding can increase biodiversity and resilience, leading to more stable and productive ecosystems. Healthy, diverse ecosystems are more resilient to climate change and human disturbance, and provide long-term ecological stability.
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Reducing Reliance on Human Management: Rewilding allows Nature to take care of itself, reducing the need for human interventions and resource extraction, which can strain ecosystems. Rewilding helps to reestablish natural predator-prey relationships and nutrient cycling, reducing the need for human intervention (e.g., pesticides, irrigation).
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Enhancing Carbon Sequestration: Rewilding projects, particularly those involving proforestation/reforestation, peatland, grassland and wetland restoration, which act as significant carbon sinks, can help mitigate climate change.
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Promoting Sustainability: Rewilding can foster a more sustainable relationship between humans and Nature by demonstrating the value of healthy ecosystems and the importance of responsible resource management.
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Addressing the Behavioural Crisis: Rewilding can also play a role in addressing the behavioural crisis [12] that drives overshoot by fostering a greater appreciation for nature and promoting more sustainable consumption patterns. It has also been proposed that rewilding can enable humans to expand our consciousness [182], and better comprehend the limits to growth [183].
Rewilding as Part of a Larger Solution
To help get below ecological overshoot, rewilding (and other NCS) must be part of an integrated approach that includes the following strategies:
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Energy transition—Cut fossil fuel use (and emissions) by moving more to renewables and reducing (minimising) total energy demand.
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Degrowth/post-growth economics—Redefine progress and prosperity.
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Circular economy—Reduce waste and resource extraction.
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Behavioural/cultural change—Shift values from consumption to stewardship.
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Relocalisation—Change from global dependency to local resilience.
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Population—Amend the culture of pronatalism to bring human numbers back within planetary limits.
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Policy—Land use, subsidies, and regulations must support regeneration over exploitation.
15. Conclusions
The term “rewilding” often elicits strong emotions, especially as presented in the media. Thus, anger is provoked that farmers will be forced to waste precious cropland, letting it return to the wild, or from fear that dangerous animals will be released into the urban environment. With equal fervour, others, taking an approving view, comprise the growing movement of guerrilla rewilders, secretly breeding butterflies, birds and beavers, and illegally releasing them (e.g., “beaver bombing”) across the countryside.
In truth, rewilding is a complex and widely encompassing proposition, which can be considered as a strategy within the natural climate solutions (NCS) [nature based solutions (NBS)] approach, aimed to restore and enhance wetlands, grasslands, forests, agricultural lands, seascapes
etc. While exact definitions may vary, a key feature is that (after some initial support) it minimises the level of human intervention/management in a given region,
instead encouraging natural processes to take the lead and self-manage, in the restoration, shaping and enhancement of natural ecosystems and of critical ecosystem functions. The resilience of such ecosystems should also be considered, especially in regard to how the impacts of a changing climate may prevail upon them.
Rewilding is informed by science, traditional ecological knowledge (TEK), and other local (indigenous) knowledge. It is a long-term process with dynamic changes occurring over time, and rather than focussing on reaching a fixed endpoint, provides a continuous journey of letting nature’s processes unfold. This can lead to increased biodiversity, amelioration of and resistance to climate change, and the provision of ecosystem services, benefitting both nature and people, including economic opportunities for local and indigenous communities, along with improved overall health and well-being.
Despite its manifold and clear benefits, rewilding (along with other NCS) is not a panacea for all our troubles, many of which are rooted in the systemic issue of human ecological overshoot, and it is this that must be addressed to begin fixing the current global polycrisis [
184].
I thank Messrs Stuart Ward and Peter Ruczynski from Reading Repair Cafe (Transition Town Reading) for providing invaluable technical support in the preparation of this manuscript.
The writing, original draft preparation, methodology, and discussion are all the work of the author, who has read and agreed to the published version of the manuscript.
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The author has received no funding for this work.
The author declares that he has no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.