before several federal agencies and the U.S. Department of the Interior, in Washington, D.C., and in 2008 the Federal government designated the polar bear as a globally threatened species.

The 2007 study projected that about two-thirds of the roughly 25,000 polar bears in the world would disappear by mid-century because of the effects of climate change and the ice melting in the Arctic. Now, in the December 2010 Nature study, Marcot and his colleagues learned that decline of the bear could be mitigated if greenhouse gas emissions are significantly reduced.

These findings may have implications for citizens and natural resource managers in the Pacific Northwest working to manage resources for a warming climate, particularly in high mountain areas.

For the past several years Marcot has collaborated with the U.S. Geological Survey's Alaska Science Center, the National Park Service, the U.S. Fish and Wildlife Service, and others on studies examining the impacts of climate change on wildlife and the environment.

The most recent study published in Nature, "Greenhouse Gas Mitigation Can Reduce Sea-ice Loss and Increase Polar Bear Persistence," was coauthored by Amstrup; Eric DeWeaver, National Science Foundation; David Douglas, U.S. Geological Survey, Alaska Science Center; Marcot; George Durner, U.S. Geological Survey; Cecilia Bitz, University of Washington; and David Bailey, National Center for Atmospheric Research, issue of Nature. It appears online at www http://www.nature.com/nature/journal/v468/n7326/full/nature09653.html

The study's key findings says Marcot are:

• The results of modeling regional polar bear populations indicate a potentially brighter future for the species if global greenhouse gas concentrations can be kept under control at levels less than those expected under current conditions.

• Sea ice habitat for polar bears will likely not face a "tipping point" of sudden catastrophic loss over the 21st century, particularly under a mitigation scenario to reduce global greenhouse gas emissions.

• Even under relatively stringent mitigation reductions in future greenhouse gas concentration, polar bears in two of the four eco-regions, constituting about 2/3 of all current polar bear numbers, will still incur at least reductions in numbers and distribution. However, the best future outcome for these populations would result from a combination of mitigation control of greenhouse gas concentration with best on-the-ground management practices to control hunting and human activities such as levels of shipping, oil and gas activities, etc.

• There will still be significant uncertainty as to the future of polar bear populations from the combination of all sources of stressors from climate change, direct human disruption, and other biological factors.

The team's study is significant. "It demonstrates for the first time that—and how—a combination of greenhouse gas mitigation and control of adverse human activities in the Arctic can lead to a more promising future for polar bear populations and their sea ice habitat," says Marcot. "It also provides specific predictions of the future, couched in terms of probabilities of polar bear population response that decision-makers could use in risk management."

Science team placing radio collars on polar bears.

(Photo Credit: Bruce Marcot, USDA Forest Service.)

Wildlife biologist Bruce Marcot is placing a radio collar on a cub.

(Photo Credit: Bruce Marcot, USDA Forest Service)