what is happening with polar bear populations?

This morning Conscious Earth had a short piece about the English swimmer who took a dip at the North Pole, and linked to the Canadian newspaper the Globe and Mail's article about the event. More interesting than the article itself was the comments section (more than 115 comments at the time I looked). The majority of the comments appear to be from disbelievers in AGW (Anthropogenic Global Warming -- which means "man made global warming" for any of my students who happen to be reading).

One particular comment caught my attention, this poster had doubts about the whole global warming idea, because she maintained that polar bear populations were growing not declining. She asked readers to "google 'taylor polar bear'". So I did that, and found a brief piece by an academic wildlife biologist studying one specific polar bear population that he claimed was increasing in numbers. This peaked my curiosity, so I googled "polar bear populations" and found some sites that should interesting any one curious on this topic.

The most detailed information about actual polar bear populations is found at IUCN (International Union for the Conservation of Nature and Natural Resources) Polar Bear Specialist Group, which brings together polar bear scientists from around the world to share information. summary of the data from the most recent conference in Seattle, posted in April 2007, provides maps, detailed explanations, and a table on the status of polar bear populations.

Polar bears are not one huge homogeneous population roaming around the Arctic, but rather live in geographically limited ranges or areas in bounded populations. Information about these geographically differentiated populations differs in quality and timeliness. Some populations have not been counted in decades, others have be surveyed often and recently. Some of the populations appear to be growing, others appear to be declining. Some appear to be stable, for the present.

The detailed explanations for each population area or range makes it clear that the impact of humans on polar bears is not limited to and perhaps not even primarily due to climate change. Polar bears are hunted by indigenous peoples and others. There is evidence in many of the geographic areas such as Baffin Bay, that the "harvest" is exceeding the reproductive capacity of the polar bear population.

The warming of the polar regions, with thinner and less extensive ice, is believed by these scientists to be contributing to declines in reproductive capacity. But equally significant is the impact of humanly created environmental toxins. "High levels of PCBs have been detected in samples of polar bears from this area [Barents Sea] which raises concern about the effects of pollutants on polar bear survival and reproduction."

So those concerned about polar bears, or any other species survival, should be focusing not just on global warming, but on other human activities such as hunting and industrial pollutants such as PCB's.

For an over view of polar bear popuations issues, check out NOAA's Artic Theme Page for the great essay by Scott L. Schliebe.