Polar bears were added to the threatened species list nearly three years ago when their icy habitat showed steady, precipitous decline because of a warming climate.
But it appears the Arctic icons aren't necessarily doomed after all, according to results of a study published in this week's issue of the journal Nature.
The findings indicate that there is no "tipping point" that would result in unstoppable loss of summer sea ice when greenhouse gas-driven warming rises above a certain threshold.
Scientists from several institutions, including the U.S. Geological Survey (USGS), the National Science Foundation (NSF), and the University of Washington, have found that if humans reduce greenhouse gas emissions significantly in the next decade or two, enough Arctic ice is likely to remain intact during late summer and early autumn for polar bears to survive.
"What we projected in 2007 was based solely on the business-as-usual greenhouse gas scenario," said Steven Amstrup, an emeritus researcher at the USGS and senior scientist at the Montana-based organization Polar Bears International. "That was a pretty dire outlook, but it didn't consider the possibility of greenhouse gas mitigation."
Amstrup is the lead author of this week's Nature paper. Co-authors are Eric DeWeaver of NSF, David Douglas and George Durner of the USGS Alaska Science Center, Bruce Marcot of the U.S. Forest Service in Oregon, Cecilia Bitz of the University of Washington, and David Bailey of the National Center for Atmospheric Research in Boulder, Colo.
The 2007 study projected that only about one-third of the world's 22,000 polar bears might be left by mid-century if dramatic Arctic ice decline continued, and that eventually polar bears could disappear completely. The work led to the 2008 listing of polar bears as a threatened species.
"Our current research provides strong evidence that it's not too late to save polar bears from extinction," said DeWeaver, an
|Contact: Cheryl Dybas|
National Science Foundation