Polar bears are creatures of the sea ice. That's why, in many European languages, they are known as ice bears, and also why, as Arctic sea ice diminishes in thickness and extent, they have become furry poster children for the potential impacts of climate change.
A 2010 study found a linear correlation between rising temperatures and falling Arctic sea ice cover; the author of that study previously predicted that polar bears could become extirpated from two-thirds of their range by the middle of this century as ever-decreasing ice extent made it increasingly difficult for them to hunt the ringed seals and other ice-associated prey on which they rely.
But, as a new paper in the journal ‘Conservation Letters‘ points out, although the overall trend in sea ice cover is clear, there is a significant amount of year-to-year variation, and while some years may prove better than average for polar bears, others may be significantly worse. The paper's authors note that "the first occurrences of these exceptionally poor years are likely to present a near-term critical challenge to polar bear conservation ... Malnutrition at previously unobserved scales may result in catastrophic population declines and numerous management challenges."
While it may be impossible to predict when those very bad years will come, they write, the Arctic nations with polar bear populations – the US, Canada, Russia, Norway and Greenland – need to begin planning now for when they do.
(As an aside, it is worth noting here that some recent articles and broadcasts have lent credence to the recurring canard that polar bear populations are doing just fine, or that, even if they aren't, there are "four to five times" more polar bears now than there were 40 years ago. Despite being treated as fact, this myth has its basis in the willful misrepresentation of comments made at a 1965 scientific meeting, as this post expertly details.)
As lead author Andrew Derocher of the University of Alberta has previously observed, one very bad ice year could leave hundreds of polar bears stranded on land for weeks on end, unable to feed. In Hudson Bay, for example, the ice melts completely in the summer, forcing bears to hunker down in cool dens ashore until it reforms in the fall.
A bad ice year could be profoundly bad news for the bear population: "Such an event could erase half of a population in a single year", Derocher has said. It could also be extremely hazardous for any nearby human communities: hungry bears can be dangerous bears. The paper's authors note that "as sea ice availability has declined, forcing bears onshore for progressively longer periods, the number of human-bear interactions has increased."
The authors point out that their goal is not to "prescribe priorities or objectives for others" but to "review anticipated concerns, options, and challenges." To that end, they lay out a number of policy options that could be considered in advance of the potential problems posed by an exceptionally low-ice year.
Some particularly malnourished bears may need to be shot, they argue; another option might be to rescue some and offer them to zoos. Providing supplemental feeding – enough to see bears through the worst periods of food deprivation – may be necessary, as may be ‘diversionary feeding': providing food that lures starving bears away from human settlements, thereby reducing the risk of encounters that could turn out to be fatal for either or both. Particularly at-risk populations may need to be thinned out, either with some bears relocated to areas with more extensive sea ice, or with some bears culled to create a population that is smaller but more viable.
They concede that many, if not all, of these proposals come with financial, practical and/or ethical concerns: For example, providing supplementary feeding may help bear survival and reduce the risk of attacks on humans in the short term, but if it sustains a population that has a poor prognosis in a world of ever-decreasing sea ice, then is it just delaying the inevitable? Or is there a moral responsibility on the part of humans to care for animals they have put at risk through global warming? The authors argue that the options are ones that Arctic nations need to be considering, with some urgency.
Photo of polar bear on the shore of Hudson Bay by Kieran Mulvaney