: the planned reintroduction of a plant or animal species and especially a keystone species or apex predator (such as the gray wolf or lynx) into a habitat from which it has disappeared (as from hunting or habitat destruction) in an effort to increase biodiversity and restore the health of an ecosystem
Wolves were the key to one of the best known examples of rewilding. In 1995, nearly 70 years after hunters had wiped them out, wolves were reintroduced to Yellowstone National Park in the US. In the absence of large predators, deer populations had burgeoned out of control … Sara Reardon, New Scientist, 1 Mar. 2014
also: the introduction of usually large animals or ecologically similar animals to a region in which they became extinct during the late Pleistocene epoch
The plan, called Pleistocene rewilding, suggests reintroducing into Arizona, the Great Plains, and elsewhere various species—such as Bactrian camels, peregrine falcons, and Old World cheetahs—that were once native to North America. Eric Jaffe, Science News, 11 Nov. 2006