Rewilding is a way to help ecosystems recover by increasing the variety of plants and animals and by letting natural processes happen again. It is different from other ways of restoring ecosystems because it tries to reduce how much humans affect nature. Rewilding also focuses on bringing back the specific interactions and functions that existed in an area before humans changed it. However, it can also include new ecosystems that have different species and interactions that did not exist before.

A main part of rewilding is letting natural processes take over instead of relying on human actions. It helps bring back groups of large animals that were once part of an ecosystem, which can help rebuild food chains and make ecosystems more stable. This happens by reintroducing large animals to an area, which helps ecosystems become more self-sustaining. These large animals shape their environments by changing how nutrients move and by creating habitats that support other plants and animals. Rewilding projects are often part of larger efforts to protect and restore habitats, and they should be based on scientific research about how humans and nature interact.

Although some people disagree about rewilding, the United Nations has included it as one of the methods needed to restore ecosystems on a large scale. The United Nations says this work must be done by 2030 as part of a global plan to protect 30% of the planet’s land and oceans.

Origin

The term "rewilding" was created by members of Earth First!, a grassroots group, and first written about in 1990. In 1998, conservation scientists Michael Soulé and Reed Noss explained rewilding in a scientific way. They described rewilding as a method to protect nature using the idea of "cores, corridors, and carnivores." Rewilding includes large protected areas, important species that help ecosystems function, and connections between habitats. This method relies on the belief that large predators help balance ecosystems. The "3Cs" approach focuses on protecting large areas of wild land, called "cores," connected by "corridors" that allow large predators to move freely. Human activities, such as building roads, are limited in these core areas. National parks and wilderness reserves are common examples of core areas. Later, Soulé and biologist John Terbough wrote about corridors in their book Continental Conservation. They found that narrow corridors might work for small animals, but large predators need wide corridors to move safely with their prey. The "3Cs" idea was further developed in 1999. Dave Foreman, a co-founder of Earth First!, later wrote a full book about rewilding as a way to protect nature.

History

Rewilding is a method used to protect working ecosystems and stop the loss of different plant and animal species. It uses research about island biogeography and the role of large carnivores in nature. In 1967, Robert H. MacArthur and Edward O. Wilson wrote The Theory of Island Biogeography, explaining that the size and broken-up nature of protected areas affect how well species survive. They said small, isolated populations are more likely to go extinct. In 1987, William D. Newmark studied animal extinctions in North American national parks, supporting this idea. These findings led to more discussions about how to best protect nature. In 1985, the Society for Conservation Biology was created, helping conservationists focus on stopping habitat loss and broken-up habitats.

People who support rewilding include individuals, small landowners, local groups, government officials, national governments, and international organizations like the International Union for Conservation of Nature. While rewilding is often praised, its growing popularity has caused disagreements, especially about large projects. Some scientists, conservation workers, government officials, and business people have criticized these efforts. However, a 2021 report for the UN Decade on Ecosystem Restoration listed rewilding as one of several methods to restore ecosystems across more than 1 billion hectares.

Guiding principles

The term rewilding has been used to describe different types of ecological restoration projects since it was first introduced. These projects vary in size and the areas where they are carried out. In 2021, the journal Conservation Biology published a paper written by 33 researchers from around the world. The paper, titled Guiding Principles for Rewilding, was created by scientists and project leaders from North America (Canada, Mexico, and the United States), Europe (Denmark, France, Hungary, the Netherlands, Switzerland, and the United Kingdom), China, and South America (Chile and Colombia). They worked together to create a shared description of rewilding and a set of ten guiding principles.

The group wrote, "Rewilding has similar goals, but different methods are used, such as protecting land, keeping ecosystems connected, removing human-made structures, and reintroducing species or replacing them with other species." They also explained that rewilding now includes many different types of projects, such as replacing large animals from the Pleistocene era, introducing new species, releasing animals born in captivity, and allowing ecosystems to recover naturally.

The group was asked by the International Union for the Conservation of Nature to create a document that described rewilding’s goals and methods on a global scale. They developed a shared definition and ten principles:

• Rewilding uses animals to help restore how species interact in food chains.
• Rewilding plans on a large scale, considering areas where animals live, how ecosystems connect, and how humans and wildlife can share space.
• Rewilding focuses on restoring natural processes, relationships, and conditions based on examples of healthy ecosystems.
• Rewilding recognizes that ecosystems are always changing.
• Rewilding should consider how climate change affects ecosystems and help reduce its impacts when possible.
• Rewilding needs support and involvement from local communities.
• Rewilding uses science, traditional knowledge, and other local knowledge to guide decisions.
• Rewilding depends on monitoring progress and adjusting plans based on feedback.
• Rewilding values all species and ecosystems for their own sake.
• Rewilding requires a major change in how humans and nature coexist.

A paper published in 2024 provided a detailed study of rewilding guidelines and interventions.

Rewilding and climate change

Rewilding can help address both the causes and effects of climate change and is considered a "natural climate solution." By creating new ecosystems and restoring existing ones, rewilding can reduce the impact of climate change and help ecosystems adapt. This happens through methods such as capturing and storing carbon, changing how the Earth reflects sunlight (called albedo), managing floods naturally, reducing the risk of wildfires, creating new habitats, and helping animals move to safer areas as the climate changes. These actions protect biodiversity and keep ecosystems strong and able to survive climate challenges.

Animals play important roles in ecosystems, such as eating plants, moving nutrients, and spreading seeds. These actions affect how much carbon is stored in soil and plants. When herbivores eat plants, they take in carbon, store it in their bodies, and release it through breathing and digestion. Studies show that rewilding large herbivores has the greatest benefit for how ecosystems function. For example, in a tropical forest in Guyana, increasing the number of mammal species from 5 to 35 led to four to five times more carbon stored in trees and soil than increasing tree species from 10 to 70. Another study found that the loss of large animals that eat fruit may reduce carbon storage in tropical forests by up to 10%. Also, animals eating plants can speed up how nutrients move through ecosystems, which helps plants grow and keeps ecosystems productive in grasslands.

Rewilding can also help reduce the risk of wildfires, which release greenhouse gases and affect how the Earth reflects sunlight. For example, when wildebeest disappeared from the Serengeti, ungrazed grass grew, leading to more frequent and severe fires. This changed the grassland from storing carbon to releasing it. When wildebeest returned, the area started storing carbon again. Rewilding also affects albedo by reducing tree and shrub cover through grazing and trampling. This exposes more ground, increases how much sunlight is reflected, and cools the local area during spring and autumn.

Other rewilding efforts, like planting trees, growing forests, and restoring wetlands, also help reduce climate change by storing carbon. While storing carbon could allow rewilding projects to be sold as carbon credits, there are concerns that carbon markets may encourage people to buy large areas of land or falsely claim environmental benefits without real action.

Types of rewilding

Passive rewilding, also called ecological rewilding, works to bring back natural processes in ecosystems by reducing or completely stopping human control over an area. For example, if a place is left untouched after being abandoned, nature can take over and return the area to its original state. In these cases, animals and plants often return and grow stronger when given the chance.

Active rewilding includes many methods that involve people helping ecosystems recover. These methods can include bringing back animals that once lived in an area, fixing habitats, and removing human-made objects or non-native animals that harm the environment.

Pleistocene rewilding is the process of introducing large animals that lived during the Pleistocene era, or animals that act like them today, to help ecosystems function better. Supporters believe that some ecosystems may be unstable because large animals that once lived there are now missing. Others argue that today’s ecosystems are not the same as they were 10,000 years ago, making this approach less practical.

Trophic rewilding is a strategy that focuses on restoring relationships between animals at different levels of the food chain, such as how top predators control the populations of other animals. This is done by reintroducing species to help ecosystems become more balanced and self-sustaining.

Urban rewilding is a type of rewilding that brings natural elements into cities to help nature and people coexist.

Elements

Ecosystem engineers are organisms that change the structure of their habitats in a clear and noticeable way. Examples of ecosystem engineers in rewilding projects include beavers, elephants, bison, elk, cattle (which are used as substitutes for extinct aurochs), and pigs (which are used as substitutes for wild boar).

A keystone species is a type of organism that has a very large impact on its environment, even if it is not very common in that area.

Apex predators may be needed in rewilding projects to prevent browsing and grazing animals from overbreeding or overfeeding, which can harm plant life and exceed the area's ability to support wildlife. This issue was observed in the Oostvaardersplassen rewilding project in the Netherlands, where large numbers of animals starved due to overpopulation. While predators are important for maintaining balance in ecosystems, scientists debate whether their control of prey populations is mainly due to direct hunting or because of the fear that predators inspire in prey (a concept called "ecology of fear"). For example, in the Serengeti, wildebeest populations are mostly limited by the availability of food, even though many predators such as lions, cheetahs, and hyenas are present.

Criticism

Some national governments and officials in international groups, such as the United Nations, believe that "excessive" rewilding—like creating large protected areas where no resource extraction is allowed—can limit people's ability to earn a living. Others argue that growing ecotourism could create jobs.

Rewilding has been criticized by some animal rights experts, such as Dale Jamieson, who say that rewilding often causes conflicts between human interests and the well-being of animals. Erica von Essen and Michael Allen, using a framework from Donaldson and Kymlicka, argue that rules about how wild animals should live are unfair and do not respect the idea that wild animals should have control over their own lives. They suggest rewilding should either fully match mainstream conservation goals or take full responsibility for caring for reintroduced animals. Ole Martin Moen believes rewilding projects should stop because they cause unnecessary suffering to wild animals and use too much money that could be used elsewhere.

Environmental historian Dolly Jørgensen says that current rewilding efforts try to ignore human history and the connection between people and nature, which could be harmful. She says rewilding should include more people to address this. Jonathan Prior and Kim J. Ward disagree, showing examples of rewilding programs that already consider the connection between humans and nature.

Some farmers oppose rewilding because they believe it leaves productive farmland unused, even though the world's population is growing. They also oppose reintroducing lynxes in the United Kingdom, fearing that lynxes might harm sheep.

Some conservationists worry that rewilding might replace efforts to protect rare species on small nature reserves, which could lead to more habitat loss and fewer species. David Nogués-Bravo and Carsten Rahbek say there is no strong evidence that rewilding works and that it might lead to "de-wilding," where species go extinct. They also say rewilding might take money away from conservation projects that are better supported by science. Large conservation groups often rely on donations based on the idea that once wildlife is gone, it cannot return. If experts say otherwise, it might confuse donors and reduce funding for conservation. Government agencies that manage land use are often influenced by loggers, ranchers, and miners, so non-profit groups often lead conservation efforts. A loss of funding could hurt wildlife protection. Some conservationists also worry that if the public believes wilderness can be restored, companies might use that idea to expand land use, claiming they can fix damage later.

In Italy's Trentino province, brown bears were reintroduced through the EU-funded Life Ursus project. While this was seen as a success, the bear population has grown to over 100, causing conflicts with people. In 2023, a bear killed Andrea Papi, the first such death in modern Italy. This event caused fear and led to calls for controlling the bear population, including killing dangerous bears. Critics say the problems come from poor management, lack of education, and not enough measures to prevent conflicts, like bear-proof trash bins. While efforts continue to balance safety and conservation, local communities are divided, with many wanting fewer bears and stronger actions against threats.

Rewilding in different locations

Both small local groups and large international conservation organizations have included rewilding in their efforts to protect and restore large wilderness areas, the paths that connect them, and important animals like top predators, meat-eating animals, and species that have a major impact on their ecosystems. Examples of these projects include the Yellowstone to Yukon Conservation Initiative in North America (also called Y2Y), the European Green Belt (built along the old Iron Curtain), projects that cross borders (such as those in southern Africa supported by the Peace Parks Foundation), community-based conservation efforts (like the wildlife areas in Namibia and Kenya), and projects focused on restoring natural habitats (such as Gondwana Link, which is regrowing native plants in a region of Australia with many unique species, and the Area de Conservacion Guanacaste, which is restoring dry tropical forests and rainforests in Costa Rica).

In North America, one major project is working to restore the grasslands of the Great Plains. The American Prairie project is reintroducing bison on private land in the Missouri Breaks area of north-central Montana. The goal is to create a prairie preserve larger than Yellowstone National Park. As of 2024, the area covered by American Prairie’s project was more than 520,000 acres.

Removing dams in the Pacific Northwest has helped restore rivers and improve the lives of salmon and other species. As noted in an article about environmental law:

“These dam removals are among the best examples of large-scale environmental cleanup in the twenty-first century. […] This has led to ongoing efforts to restore four river systems: the Elwha and White Salmon in Washington, and the Sandy and Rogue in Oregon.”

Yellowstone to Yukon (Y2Y) was officially started in 1997. The project aimed to create a protected land corridor stretching from Canada’s Yukon territory, through national parks like Waterton and Glacier, to the Greater Yellowstone region in the northern Rocky Mountains. Supporters of the project tried to stop the building of roads and other human developments that might block the movement of large predators like wolves and grizzly bears. Y2Y used lobbying and education to share its goals and involve the public. Organizers held meetings between rewilding groups in Canada and the United States, helped conservationists and Native American groups talk about shared goals, and kept the project in the news by writing about it in newspapers like the New York Times and the Washington Post. Activists working on the project successfully pushed for 24 structures that allow wildlife to cross highways safely in the Banff area.

Y2Y inspired other conservation groups to focus more on encouraging governments to act. It also led to more planning for wildlife corridors across North America. The South Coast Wildlands Project helped the California State Parks Agency buy a 700-acre area that was planned for development. The Algonquin to Adirondack initiative, modeled after Y2Y, has studied ways to improve connections between habitats around the Great Lakes. Conservation groups in the United States and Canada have worked together to plan areas in the ocean from Baja California to the Bering Sea, allowing both countries to protect shared wildlife.

Many projects have been created to protect North America’s carnivores, a key part of the “3 C’s” approach to rewilding. Reed Noss, an early supporter of rewilding, began designing protected areas in the 1980s to help Florida’s largest predators, the Florida panther and the Florida black bear. His plan suggested that 60% of Florida’s land should be set aside for wildlife reserves. This idea was so influential that the Florida State legislature spent $3.2 billion to buy land for a network of reserves and paths connecting them.

At the same time, a group in Washington D.C. called Defenders of Wildlife started promoting the protection of predators like grizzly bears, wolves, and river otters across the country. In 1987, they created the Bailey Wildlife Foundation Wolf Compensation Trust to pay ranchers for losing livestock to predators, hoping to gain support from farmers, who often oppose the conservation of large predators. In 1998, they launched a program to help farmers protect their animals without harming predators, such as by using fences and alarms. However, this effort did not help increase the number of native wolves, as some people still shot wolves, both illegally and with permission from the USFWS.

Fresh Kills landfill on Staten Island once held 150 million tons of trash. Between 2001 and 2006, plans were made to turn it into a 2,200-acre park, the largest new park in New York State in over 100 years. Construction started in 2008 to restore the area to its original wetland ecosystem, including open water, swamps, prairies, and wildflower meadows. Part of the plan involved removing invasive reed plants and replacing them with native marsh grasses. The project is expected to take up to 30 years to complete, with the goal of combining nature restoration with recreational spaces.

While planning for Fresh Kills Park, New York State also started a larger project to protect the ecosystem around Staten Island by restoring the Hudson River. In 2005, the groups involved set goals to improve the river’s fish populations, clean up pollution, and protect habitats along the river. When the project is finished, it will cover 50,000 acres with six different types of habitats.

In the Mexican state of Sonora, the Northern Jaguar Project bought 45,000 acres of land by 2007 to protect the northernmost breeding population of jaguars. The group also encouraged local people to help monitor jaguars by offering a $500 reward for each photo of a living jaguar taken by ranch owners who agreed not to shoot jaguars on their property. In its first year, the program paid $6,500 for photos of jaguars, mountain lions, and ocelots.

In the early 1990s, the Wildlife Conservation Society proposed a plan for a major corridor project connecting reserves, parks, and forests across seven Central American countries and five Mexican states. The plan was called “Paseo Pantera,” or “the path of the panther,” because mountain lions move through the area. The plan caused controversy, as some indigenous people worried their land would be taken for parks, and others believed the project prioritized the environment over human needs. These concerns led to changes in the plan, and in 1997, it was renamed the “Mesoamerican Biological Corridor” to also support local communities and economies.

Even after the changes, the Mesoamerican Corridor had challenges, especially with how land was used. The plan required agreements with many villages to decide how protected areas would be managed, where hunting and fishing would be allowed, and how rules would be enforced. Rural people were not satisfied with the unclear details, so progress was slow. In 2005, the Central American Free Trade Agreement