Smithsonian.com

Two male polar bears spar near Hudson Bay. (Credit: Steven Amstrup, Polar Bears International)

In 2007, scientists from the U.S. Geological Survey said that if humans didn’t do anything to reduce greenhouse gas emissions, two-thirds of the world’s polar bears could be gone by the middle of this century. Now a new study has addressed the next question: Is there still time to help the bears? The study, published this week in Nature, provides some hope, and scientists have concluded that if we’re able to substantially reduce our emissions, we may be able to save enough sea ice to save the polar bear.

Polar bears (Ursus maritimus) depend on the sea ice to reach their prey, bearded seals and ring seals. As the summer sea ice has disappeared and the bears have lost opportunities for hunting, scientists have noted a decline in polar bear physical condition, survival and population size. The 2007 study concluded that under our current levels of greenhouse gas emissions, the summer sea ice would continue its precipitous decline, one that the polar bears would find hard to survive.

The latest study examined what would happen to the sea ice under other emissions scenarios, and whether there was some tipping point, a temperature increase beyond which the polar bear population would inevitably crash. They concluded that as long as temperatures did not increase beyond 2.25 degrees Fahrenheit, there would be enough sea ice for the polar bear population to survive through the end of the century.

“There’s still a fairly high probability … that polar bears could disappear” in two of the three regions where they live, said the study’s lead author Steven Amstrup, an emeritus researcher at the USGS and senior scientist with Polar Bears International. “But with mitigation and aggressive management of hunting and other direct bear-human interactions, the probability of extinction would now be lower than the probability that polar bear numbers will simply be reduced. …The benefit of mitigation to polar bears is substantial.”