With climate change increasingly threatening the survival of plants and animals, scientists say it may become necessary to move some species to save them.

“When I first brought up this idea some 10 years ago in conservation meetings, most people were horrified,” said Camille Parmesan, a biology professor at the University of Texas.”But now, as the reality of global warming sinks in, and species are already becoming endangered and even going extinct because of climate change, I’m seeing a new willingness in the conservation community to at least talk about the possibility of helping out species by moving them around.”

Dubbed assisted colonization or assisted migration, the idea is to decide how severe the threat is to various species, and if they need help, rescuing them by moving them someplace new.Suggestions of how this could be applied include moving African big game to the American Great Plains, or airlifting endangered species from one mountaintop to another as climate zones shrink.

Once dismissed as wrongheaded and dangerous, assisted colonization is now being discussed by serious conservationists. And no wonder: Caught between climate change and human pressure, species are going extinct 100 times faster than at any point in human history.And some scientists say that figure is too conservative. The real extinction rate, they say, is a full 1,000 times higher than normal. The last time such annihilation took place was during the time of the dinosaurs. And though many conservationists say that saving species by transplanting them is foolish, others say there’s no choice.

“It’s a showdown. The impacts of climate change on animals have become apparent. And it’s time to decide whether we’re going to do something,” said Notre Dame ecologist Jessica Hellmann, co-author of an influential 2007 Conservation Biology paper, A Framework for Debate of Assisted Migration in an Era of Climate Change. “Reducing CO2 is vital, but we might have to step in and intervene.”

“They want the world to be what it was before. But it’s not going to happen,” said Australian ecologist Hugh Possingham, co-author of an assisted-colonization article published in Science, Assisted Colonization and Rapid Climate Change.

The language of Possingham’s paper is understated — its centerpiece is a risk-benefit flow chart — but the recommendations are radical. He proposes a systematic analysis of Earth’s threatened species, identifying those suitable for last-ditch uprooting.That one of the scientific world’s most respected publications carries such a proposal marks a sea-level shift in conservationist consciousness, say researchers. Others have weighed the idea, but Possingham’s team came down firmly in favour.

Adding to the momentum, the Ecological Society of America‘s annual meeting in August will be preceded by a three-day discussion of assisted colonization, by ecologists, policy wonks and lawyers.

Still, it’s an idea that makes conservation biologists nervous.

There are plenty of risks in moving plants and animals to new locations. They may not survive, or they may become invasive, growing wildly without predators and crowding out natives of their new location.And it’s not possible to relocate every species that may need it, so how to decide who gets moved and who gets left behind to become extinct?

Stanford biologist Terry Root has been traveling the country urging her colleagues to come up with a plan for “triage” to decide which species should be saved from global warming and which can’t. After other biologists complained about the word “triage,” Root said she now calls it prioritizing which species should be saved.”We’ve got to work on the ones we have a prayer of saving,” Root said.

Some species biologists will have to write off, such as the threatened and endangered species of the Sky Islands in Arizona and New Mexico because “They don’t have any place to move to.Those species are functionally extinct right now,” Root said. “They’re toast.”

When deciding which species to save and which to watch die, Root said one key is how unique it is. That’s why she said she’d save the odd-looking Tuatara of New Zealand, a lizard-like creature with almost no living relatives, over the common sparrow.

But not everyone is in a rush. “I think it’s a bad idea,” said Duke University biologist Jason McLachlan, also a co-author of the Conservation Biology paper. “There are a million examples of invasive species introduced with good intentions that caused all sorts of damage.”Accounts of destruction wrought by invasive species are legion, from wild boars in the southern United States and zebra mussels in the Great Lakes to cane toads in Australia and mongeese in Hawaii. An endangered species that now seems sympathetic could quickly become a villain.

The perfect example of McLachlan’s objections is the solution touted by some researchers to save polar bears: move them to the Antarctic. Cost and logistics aside, the bears would wreak havoc in an ecosystem unprepared for them.”Antarctic penguins and seals aren’t adapted to surface predators,” explained Steven Amstrup, the chief U.S. Geological Survey polar-bear researcher. “The bears would have a field day for a while, because they could walk right up to them and eat them. For a short period of time, it would be great, but in the end the whole system would probably collapse.”

But assisted-colonization proponents believe their animals, unlike other invasive species, would be carefully selected and their effects anticipated.”You work out what the risks are before you take action,” said Possingham. “You go through these decision trees, and start by doing some trials under very controlled circumstances, then we’ll learn about it.”

“Things could still go wrong”, said Hellmann, “but the consequences pale in comparison to those of climate change and inaction. And for animals whose natural habitat has been eradicated, or who live — as did the golden toad of Costa Rica’s cloud forest — in rapidly changing places from which they cannot escape, there may be no other option.”

“If all other conservation methods fail, and evidence shows that a species is in danger of extinction, then assisted migration becomes an option that we should consider seriously,” said Nature Conservancy ecologist Patrick Gonzalez.

McLachlan, however, has other reasons for opposition. Assisted colonization could be seen as a quick-fix panacea, distracting people from the necessary task of preserving habitat and braking climate change. More philosophically, there’s something troubling about treating nature as a zoological theme park.”We’re destroying any semblance of the idea that a place has its own biota and history,” he said. “It’s not just saving a couple whooping cranes, it’s redesigning the entire biota of Earth. And that’s incredibly creepy to me.”

Hellmann agrees that assisted colonization could be mistaken as a convenient solution. But the purity of nature, she said, is now a myth.”You can find signatures of humanity in the deepest jungles and remote locations. This idea of pristine nature doesn’t really apply,” she said. “If assisted colonization will have benefits, it seems strange not to cross some arbitrary line.”

“Ultimately, the decision about whether to actively assist the movement of a species into new territories will rest on ethical and aesthetic grounds as much as on hard science,” Camille Parmesan said in a statement.”Passively assisting coral reef migration may be acceptable, but transplanting polar bears to Antarctica would not be acceptable.Conservation has never been an exact science, but preserving biodiversity in the face of climate change is likely to require a fundamental rethinking of what it means to preserve biodiversity.”