Rapid climate change is forcing scientists to consider for the first time whether to help wildlife relocate to places where they are not currently found, says a group of international researchers who have created a tool for evaluating such relocations.

Assisted wildlife migration was once a taboo conservation strategy because of its potential for harming ecosystems. It is still highly controversial because it's not clear that we know enough to predict what will happen.

Relocated species might overpopulate their new habitats, cause extinctions of local species, or clog water pipes as invasive zebra mussels have done in the Great Lakes.

But over the past five to 10 years, some conservationists and groups have started helping wildlife migrate or are currently considering doing so, say the researchers, who hail from Stellenbosch University in South Africa, Indiana's University of Notre Dame, Brown University in Rhode Island and University of California at Davis.

The group has come up with a tool to evaluate the probability of successfully relocating animals, its potential for harming ecosystems, its costs, its potential for triggering violations of endangered species' acts, and the social and cultural importance of impacted species.

Their scoring strategy is described in the May 25, 2009, issue of the Proceedings of the National Academy of Sciences.

The scientists acknowledge their proposed strategy is not without its difficulties. The scoring system still sometimes pits members of the working group against one another, they say.

But they argue a "do nothing" response to climate change involves significant risks.

"We have previously been able to say, 'let nature run its course,'" University of Notre Dame conservation biologist Jessica Hellmann, said in a release. "But because humans have already changed the world, there is no letting nature run its course anymore. Now, action, like inaction, has potential negative consequences."

Many species have survived previous, slower periods of climate change by evolving or by moving to more hospitable habitats via their own power.

But today, animals are faced with a double-whammy. Climate change is happening so fast that it's hard for them to find suitable new homes, and escape routes to new habitat are often cut off by cities and other man-made structures.

Without help, animals can become trapped in habitats that have become too hot or too dry for them.