Pleistocene Park: Does re-wilding North America represent sound conservation for the 21st century?

A group of conservation biologists recently proposed to populate western North America with African and Asian megafauna, including lions, elephants, cheetahs, and camels, to create a facsimile of a species assemblage that disappeared from the continent some 13,000 years ago. The goals of this program, known as "Pleistocene re-wilding", are to restore some of the evolutionary and ecological potential that was lost from North America during the Pleistocene extinctions, and help prevent the extinction of selected African and Asian mammals. Pleistocene re-wilders justify this conservation strategy on ethical and aesthetic grounds, arguing that humans have a moral responsibility to make amends for overexploitation by our ancestors. They believe that the flora of many North American terrestrial ecosystems has gone basically unchanged since the end of the Pleistocene, so re-wilding would help restore evolutionary and ecological potential and improve ecosystem functioning. This paper discusses some of the pros and cons of this proposal, including the ethical, aesthetic, ecological, and evolutionary issues, assesses its potential economic and political impacts on other conservation practices, both in North America and elsewhere, and reviews the realities of large mammal reintroductions. It is concluded that Pleistocene re-wilding with exotic species will not restore the evolutionary or ecological potential of native North American species nor extinct Pleistocene megafauna and their ancient ecosystems, but may instead jeopardize indigenous species and North American ecosystems. Resources would be better spent on preserving threatened organisms in their native habitats and reintroducing them to places in their historical ranges from which they were only recently extirpated.