“America’s ecosystems have evolved since the Pleistocene; the consequences of introductions
of exotic megafauna to the continent cannot be predicted.”
—Dustin Rubenstein et al.
In “Restoring America’s Big, Wild Animals,” C. Josh Donlan reiterates a proposal to populate the American West with species (lions, cheetahs and elephants) he considers “proxies” for extinct megafauna present there in the Pleistocene. Donlan mentions some of our concerns, published in Biological Conservation in October 2006, but dismisses them unfairly. For example, we referenced Jurassic Park to emphasize his plan’s sensationalism, not out of confusion about evolutionary timescales. There is a fundamental difference between “rewilding” and “Pleistocene rewilding.” Rewilding involves reintroducing species extirpated within the past few hundred years to their native habitats; neither species nor habitats can have changed much in that time. The successful reintroduction of the Bolson tortoise to New Mexico is an example of this. Pleistocene rewilding would involve introducing exotic species Donlan hopes will fill the ecological roles of their Pleistocene ancestors.