Environment

Climate Change Killing Polar Bears After All

by ScienceDave | November 23, 2007 at 03:24 pm

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Sure, a UK judge has deemed that climate change has not led to an increase in polar bear drownings, as stated in Gore's An Inconvenient Truth, due to increased melting sea ice.

However, recently published work indicates melting sea ice is affecting polar bear population numbers after all; juveniles and the elderly are at the highest risk. From the paper:

"Survival of juvenile, subadult, and senescent-adult polar bears was correlated with spring sea ice breakup date, which was variable among years and occurred approximately 3 weeks earlier in 2004 than in 1984. We propose that this correlation provides evidence for a causal association between earlier sea ice breakup (due to climatic warming) and decreased polar bear survival."

Nature has reported on the results (subscription required):

Biologists were already worried about this population of bears. Back in 1999, before the population started to decline, the same census found that bears became thin in years with less ice.

Polar bears fast through their summer by stocking up on weanling ring seals. In early spring, the bears feast on unwary seal pups until the ice breaks up, storing up much of the energy they’ll need to get by. In years when the ice breaks early, the less-able hunters catch fewer seals than they need.

Now it seems the hunger is leading to deaths. “It’s scary,” says Martyn Obbard, who keeps tabs on polar bears at the southern edge of Hudson Bay for the Ontario Ministry of Natural Resources in Peterborough, but did not participate in this study. “The evidence and their conclusions are solid.”