What Is Rewilding and Can It Restore Our Ecosystems?

Rewilding is a form of conservation and ecological restoration that aims to improve biodiversity and ecosystem health by restoring natural processes. In addition, this conservation strategy aims to provide connectivity between natural processes and ecosystem health, and reintroduce apex predators and keystone species.

Rewilding comes down to the conservation of the three C’s–cores, corridors, and carnivores. Interest in rewilding and conservation biology has expanded in the 21st century, and supporters of the strategy include NGOs, individuals, landowners, and governments.

How Rewilding Works

While there aren’t many policies that specifically focus on rewilding, there are norms that exist around its implementation. Examples include:

• Protecting and expanding ancient woodlands to allow a variety of wildlife to disperse and to increase carbon storage. Rewilding in these areas focuses on natural processes taking their course, including the natural succession of open habitat, fluctuations in population abundance, and allowing species to exist without human interference. 
• Reintroducing missing species back into ecosystems to fill crucial gaps and restore the food chain. This would reforge the relationship between predators and prey.
• Reducing populations of grazing animals such as cattle in order to allow trees and other vegetation to grow back.
• Introducing beavers into ecosystems to build natural dams that reduce downstream flooding, increase water retention, and clean water. Beavers also help to boost biodiversity and store carbon.
• Removing dams so that fish are able to move more freely and to allow natural processes such as erosion to reestablish themselves.
• Reconnecting rivers to floodplains has the effect of slowing the flow of the river, lessening instances of floods, and creating habitats for fish and other aquatic wildlife.
• Putting aside large areas for nature to evolve on its own terms, without human interference.
• Restoring marine ecosystems such as coral reefs, seagrass, and oyster beds to increase biodiversity and carbon storage.

Benefits and Criticisms of Rewilding

Rewilding offers an abundance of ecological, social, and economic benefits. However, it also has been highly criticized by conservation scientists regarding whether rewilding is good for species in the first place.

Benefits

The first benefit comes with its definition: Rewilding helps to reduce the mass extinction of species by giving nature the opportunity to reestablish its natural processes and biodiversity. As human activity is currently degrading ecosystems at unprecedented rates, rewilding helps to lessen this impact. Additionally, rewilded ecosystems help to mitigate climate change as they increase carbon storage and carbon removal from the atmosphere.

Rewilding also helps to protect against natural disasters such as soil erosion, flood risk, and forest fires. For example, rewilded trees help to delay the rate at which rainwater reaches the forest floor and the tree roots act as channels to draw rainwater underground, thus preventing flooding.

Criticisms

The main criticism of rewilding is there are many uncertainties associated with it. It is not always fully known if extirpated species will do well if placed back in a previous environment. This is especially the case with Pleistocene rewilding, as species are reintroduced to ecosystems where they have been missing for thousands of years. Uncertainties exist around where these species will reside, what they will eat, how they will breed, etc. Additionally, it is not always clear how other species will react to a reintroduced species.

An example of a failed rewilding attempt was at Oostvaadersplassen in the Netherlands. Wild-living cattle, horses, and red deer were brought to this reserve to mimic the grazing of extinct herbivores such as aurochs. However, the animals were left to starve and up to 30% of the animals died over winter periods due to food scarcity.

Types of Rewilding

There are three different types of rewilding, each featuring varying processes and effectiveness: Pleistocene rewilding, passive rewilding, and translocation rewilding.

Pleistocene Rewilding

Pleistocene rewilding refers to the reintroduction of species from the Pleistocene era, or the Ice Age, back into ecosystems. Towards the end of the Pleistocene era, nearly all megafauna became extinct in what is known as the Quaternary extinction.

Advocates of this type of rewilding state that this extinction event left ecosystems unbalanced. Biologist Tim Flannery states that, since the extinction of megafauna 12,000 years ago, the Australian continent has not had ecosystem balance. Therefore, because the Pleistocene era occurred thousands of years ago, this form of rewilding potentially involves introducing completely foreign species into an ecosystem.

The reintroduction of wolves and bison to Yellowstone National Park is an example of Pleistocene rewilding. These species were driven to extinction by overhunting and were brought back into the Yellowstone ecosystem after being deemed vital for a healthy functioning ecosystem by park managers.

Passive Rewilding

This type of rewilding aims to reduce human intervention in ecosystems with the goal of letting nature develop on its own. This approach requires little to no human interference in ecosystems and allows natural processes to be restored. For example, passive rewilding would include stepping away from a plot of cultivated land and letting the natural landscape flourish.

Translocation Rewilding

Translocation rewilding involves introducing species that have more recently been lost from ecosystems. It aims to restore altered processes and ecosystems functions by reintroducing current descendants of lost species. An example of this type can be seen in the introduction of the beaver to build dams in the United Kingdom and the Netherlands.

There are two different types of translocation rewilding. The first is reinforcements, which involve the release of a species into an existing population to enhance viability and survival. The second is reintroductions, also referred to as tropic rewilding, which involves reviving a species in an area after local extinction.

Successful Examples

One of the most well-known examples of rewilding is the reintroduction of the wolf into Yellowstone National Park. The wolf is a keystone species, which means that the plants and animals within the broader Yellowstone ecosystem depend on the wolf for survival. Before the wolf was reintroduced, elk over-grazed the local vegetation. The reintroduction thus decreased elk numbers, which has allowed species such as cottonwood and aspen to recover. There are currently 11 packs and 108 wolves reported, as of 2016, whereas there were none before the 1995 reintroduction.

Another successful example is the revival of the European bison in nature reserves in the Netherlands. The European bison went extinct in the wild in 1919, but now thousands of bison graze the forests and plains of the Netherlands. This species was chosen for rewilding efforts due to the vital role that it plays in a European forest and plain ecosystems. These animals eat and fertilize grasses, which become food for deer and other animals. The nature reserves are now experiencing great environmental benefits from the grazing of the bison, resulting in an abundance of flora and fauna.

The Siberian Tiger Introduction Project in South Korea was introduced as DNA tests revealed that the Siberian and Korean Tiger were the same species. These tigers are keystone species as they help to keep populations of prey species in check. A “tiger forest” was created in the attempt to preserve the Siberian tiger and it will contribute to WWF’s goal to have 6000 tigers in the wild globally by 2022.