Five years ago, US conservation biologist Josh Donlan got some people howling with a controversial article in the scientific journal Nature. Almost literally howling, since the subject was his proposal to "re-wild" the Great Plains.

Re-wild, meaning to re-locate wild animals, including predators such as lions and cheetahs - from Africa to vast, fenced "ecological history parks" on the American prairie.

The goal would be to save species that are endangered because of their ever-shrinking habitat in Africa and to re-invigorate the predator-prey pecking order on the plains.

The Nature article noted that 13,000 years ago, at the end of the Pleistocene geological era, the North American prairie teemed with big vertebrates such as woolly mammoths, five species of horses and an early version of the cheetah. They were all hunted to extinction when humans arrived.

Saber-tooth tigers and the like are gone for good. But those who favor the re-wilding idea say today's threatened elephants, camels, and big cats could avoid the same fate on the American plains. And what fabulous photographic safari attractions they would make for tourists.

Critics had fun with all this. One writer envisioned elephants in the driveway throughout the Midwest. Someone else pictured camels frozen solid in prairie winter snowdrifts.

But other conservationists said re-wilding deserved a fair look. The Nature Conservancy, for instance, gave it a "hats off" salute for being provocative, though it added, "If you want to think big, why not think big in Africa?"

So it goes without saying that there are no elephants outside of circuses and zoos in Kansas or Oklahoma. But small steps have been made. Former television magnate Ted Turner is modestly re-wilding his New Mexico ranch, where he has brought back a giant, nearly extinct, breed of tortoise.

Fine, say sheep and cattle ranchers. But inviting hungry lions to roam America's grasslands would be insane, they say - fence or no fence.

cheetah: a wild animal of the cat family, with black spots. It runs very fast. 猎豹

Pleistocene: 更新世的

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（来源：VOA 编辑：崔旭燕）