

Credit: Andrew Derocher.

As the erstwhile icon of climate change, polar bears have been a very … political subject. Conservatives love to lambaste Al Gore over his claims about drowning polar bears in his 2006 film An Inconvenient Truth. The Department of the Interior even launched an investigation into a U.S. researcher who had authored a 2006 study describing several polar bear drownings (he later reached a $ 100,000 settlement with the agency).

Meanwhile, politics aside, the habitat in which polar bears live -- the Arctic -- has kept changing and changing. Arctic sea ice hit a dramatic low in 2007 and an even more dramatic one in 2012:

This is why despite all the political theater, there is still very good reason to believe that polar bears are threatened by global warming -- an interpretation that two recent studies have now reaffirmed.

Just last week, a study by scientists from the U.S. Fish and Wildlife Service, U.S. Geological Survey, and several other organizations found that in the Southern Beaufort Sea region of the U.S. and Canadian Arctic, polar bears saw a 25 to 50 percent decline in the decade from 2001 to 2010.

And today, a new study out in PLOS One further underscores polar bear risks. Using a regionally focused climate model, the researchers projected that under a business as usual scenario for global warming, sea ice in the Canadian Arctic Archipelago will decline markedly, leaving long periods each year when there isn’t any ice. The consequences for polar bears, it notes, could be "starvation and reproductive failure across the entire Archipelago by the year 2100."

"The Canadian Arctic Archipelago, where our study is focused, is believed to be the area of the Arctic basin that will retain sufficiently long ice-covered seasons to support polar bears the longest," says lead study author Stephen Hamilton of the University of Alberta in Edmonton. "Our findings suggest a possible 9-21 % of adult male starvation, and 55-100 % reproductive failure by the year 2100 ... throughout the Archipelago. We would expect that conditions outside the Archipelago should be worse."

Recently, there have been hints that polar bears may be able to adapt to changing Arctic conditions by changing their food sources -- for instance, shifting from a reliance on eating seals (which requires hunting atop the ice) to catching geese and caribou. However, Hamilton doesn't think lifestyle shifts will be enough to save the bears.

"While an individual may learn a trick or two, in order for the polar bear species to adapt, sufficient time must pass for genetic traits that are helpful in warming conditions to be passed on to younger generations," he says. "The generation time of a polar bear is much too long to keep up with the rate of change we are seeing."

Which is why, as is the case with most endangered or threatened species, it ultimately all comes down to whether or not the habitat in which they live -- the habitat they evolved in and adapted to -- will be preserved. "Polar bears need sea ice, so losing the ice means losing the bears," says Hamilton.