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The polar bear's resilience should have meant the end of its use as an icon of global warming doom

One reason that the 2007 predictions of future polar bear survival were so far off base is that the model developed by American biologist Steven Amstrup (now at Polar Bears International, an NGO) assumed any polar bear population decline would be caused by less summer ice, despite the Beaufort Sea experience. Moreover, Amstrup and fellow modelers were overly confident in their claim that summer ice was critical for the polar bear’s survival and they had little data on which to base their assumption that less summer ice would devastate the polar bears’ prey.

Consequently, many scientists were surprised when other researchers subsequently found that ringed and bearded seals (the primary prey of polar bears) north of the Bering Strait especially thrived with a longer open-water season, which is particularly conducive to fishing: These seals do most of their feeding in summer. More food for seals in summer means more fat seal pups for polar bears to eat the following spring, a result that’s probably true throughout the Arctic.

As long as polar bears have lots of baby seals to eat in spring, they get fat enough to survive even a longer-than-usual summer fast. And while it’s true that studies in some regions show polar bears are lighter in weight than they were in the 1980s, there is no evidence that more individuals are starving to death or becoming too thin to reproduce because of less summer ice.

Not all bears get enough to eat in the spring, of course. Starvation has always been the leading natural cause of death for polar bears, due to a number of factors including competition, injury, tooth decay and illness. Some cancers induce a muscle-wasting syndrome that leads to faster-than-usual weight loss. This is likely what happened to the emaciated Baffin Island bear captured on video in July 2017 and promoted by National Geographic late last year. The videographers claimed it showed what starvation due to sea-ice loss looked like — an implausible conclusion given the time of year, the isolated nature of the incident, and the fact that sea ice that year was no more reduced than previously.