An Imperfect Symbol
The largest of the bear subspecies and a powerful apex predator, the charismatic polar bear became the poster animal for climate change.
Al Gore’s 2006 film, “An Inconvenient Truth,” which depicted a lone polar bear struggling in a virtually iceless Arctic sea, tied the bears to climate change in many people’s minds. And the federal government’s 2008 decision to list polar bears as threatened under the Endangered Species Act — a designation based in part on the future danger posed by a loss of sea ice — cemented the link.
But even as the polar bear’s symbolic role has raised awareness, some scientists say it has also oversimplified the bears’ plight and unwittingly opened the door to attacks by climate denialists.
“When you’re using it as a marketing tool and to bring in donations, there can be a tendency to lose the nuance in the message,” said Todd Atwood, a research wildlife biologist at the United States Geological Survey’s Alaska Science Center. “And with polar bears in particular, I think the nuances are important.”
Few scientists dispute that in the long run — barring definitive action by countries to curb global greenhouse gas emissions — polar bears are in trouble, and experts have predicted that the number will decrease with continued sea ice loss. A 2015 assessment for the International Union for Conservation of Nature’s Red List projected a reduction of over 30 percent in the number of polar bears by 2050, while noting that there was uncertainty about how extensive or rapid the decline of the bears — or the ice — would be. A version of the assessment was published online Dec. 7 in the journal Biology Letters.
But the effect of climate change in the shorter term is less clear cut, and a populationwide decline is not yet apparent.
Nineteen subpopulations of polar bears inhabit five countries that ring the Arctic Circle — Canada, the United States, Norway, Greenland and Russia.
Of those, three populations, including the polar bears in the southern Beaufort Sea, are falling in number.
But six other populations are stable. One is increasing. And scientists have so little information about the remaining nine that they are unable to gauge their numbers or their health.
In their analysis, the researchers who conducted the Red List assessment concluded that polar bears should remain listed as “vulnerable,” rather than be moved up to a more endangered category.
Yet numbers aside, scientists are seeing other, more subtle indicators that the species is at increasing risk, including changes in the bears’ physical condition, body size, reproduction and survival rates. And scientists have linked some of these changes to a loss of sea ice and an increase in ice-free days in the areas where the bears live.
Climate-change denialists have seized on the uncertainties in the science to argue that polar bears are doing fine and that sea ice loss does not pose a threat to their survival. But wildlife biologists say there is little question that the trend, for both sea ice and polar bears, is downward. The decline of a species, they note, is never a steady march to extinction.
“It’s not going to happen in a smooth, linear way,” said Eric Regehr, a biologist at the federal Fish and Wildlife Service in Anchorage who took part in the 2015 assessment and presented the findings at a meeting in June of the International Union’s Polar Bear Specialist Group.