People hoping to glimpse lions, cheetahs, elephants and other megafauna in their natural environment must journey to Africa's wildlife reserves. But if one group of ecologists and conservationists gets its way, safari-goers could soon head for the Great Plains of the U.S. instead.

In a report published today in the journal Nature, Josh Donlan of Cornell University and his colleagues propose replacing the large carnivores and herbivores that disappeared from North America 13,000 years ago, at the end of the Pleistocene epoch. Noting that humans likely had a part in these extinctions and that our subsequent activities have stunted the evolutionary potential of most remaining megafauna, the scientists say we have an ethical responsibility to address these problems. But rather than just managing extinction, they argue, conservation biology should aim to actively restore natural processes.

Large-bodied vertebrates commonly play key roles in maintaining biodiversity and North America's extinct megafauna probably figured importantly in the evolution of animals that are around today, the team asserts. The researchers cite the pronghorn--the fastest land animal on the continent--as an example. This animal's remarkable fleet-footedness, they observe, was almost certainly shaped by the now-extinct American cheetah.

Under the new plan, called Pleistocene "re-wilding," close cousins and counterparts of the lost beasts, mostly from Africa, would be released into large, protected tracts of land and allowed to roam freely. Ideally, such actions would not only give parts of North America back an approximation of their long-ago megafauna diversity, they would also help save animals such as the African cheetah from extinction.

Pleistocene re-wilding is also justified on economic grounds, Donlan and his co-authors contend. They envision creating "ecological history parks" in economically depressed regions of the Great Plains, which would create management and tourism jobs for people living in the surrounding towns.

"Obviously, gaining public acceptance is going to be a huge issue, especially when you talk about reintroducing predators," Donlan admits. "There are going to have to be some major attitude shifts. That includes realizing predation is a natural role, and that people are going to have to take precautions."