Rewilding is bringing animals or plants back to an area from where they have disappeared. The point of this is to restore biodiversity and processes that have been lost in some ecosystems. For example: when bringing back wolves to an area that helps control some populations (like moose) and allows others to recover (like plants).
Ecosystems are healthy when they are home to biodiverse plants and animals. Each type of organism in an ecosystem helps keep the balance, from the smallest ant to the largest tree. When some types of plants and animals disappear from an ecosystem, the other plants and animals can suffer. If wolves disappear from a forest, then there can be too many hooved animals like elk, which can damage the trees and rivers and drive out other animals, like beavers. Rewilding tries to bring back balance to make an area healthy again.
An area has three requirements to be able to support a re-introduction. These are: (1) large, protected reserves; (2) connectivity; and (3) keystone species. Large, protected reserves are areas like National Parks where animals can find areas without people and cars. Connectivity means that animals can move from one reserve to another. This way, animals are not stuck in an area that is too small. Instead, they can move from an area like a national park to a nearby national forest without crossing paths with many people. This is important to keep a variety of genes in the animal’s community. Connectivity is also important so that the animals can find enough food. Keystone species are important because they keep an area healthy and balanced. They are species that have a larger impact on the ecosystem than other species. They might provide resources to other species or keep numbers of other species in check.