Other Challenges for Polar Bears

1/5/2012 8:15:23 PM

Other Challenges for Polar Bears

Bear on ice
 

It's easy to lose sight of other threats to polar bears when global warming keeps reminding us of how badly we need to act. Climate change is the main threat to polar bears in the coming decades. Over-harvesting, shipping, development, and pollution, however, all impact polar bears and will be important in years to come as they interact with a warming climate.

Consider the over 200 ice-breaking ships that pass through polar bear habitat in Foxe Basin every year and right through winter - crushing ice and seals as they pass from the North Atlantic to the Mary River iron ore mine on Baffin Island in northern Canada. What are the impacts on polar bears? Nobody knows and even the environmental assessment didn't seriously address the question.

Thea BechshÌüft of Aarhus University recently defended her Ph.D. in Roskilde, Denmark, and I was invited to be an examiner. The thesis is a wonderful investigation, but sobering in its results. It's clear that pollution affects the inner workings of polar bears. East Greenland, where Thea's study was based, is one of the most polluted areas in the Arctic. The pollution all comes from the south and is transported northward on air and ocean currents.

The thesis focused on the effects of pollution on vitamin levels (A and E) and hormones as biomarkers of contaminant effects. The research revealed clear but complex linkages between pollution and the biomarkers. In summary, vitamins and hormones are affected by pollution. Of great concern, the thesis found that a stress hormone (cortisol) in polar bears was higher in warmer years. Stress is not good in any organism, and the thesis concluded that the findings add to the weight of evidence that climate change and POPs [persistent organic pollutants] are the major ecological stress factors for East Greenland polar bears.

While scientists here in Canada  have focused on the polar bears in Hudson Bay and the Beaufort Sea, our colleagues in Denmark and Greenland have grave concerns about the bears in East Greenland.

Photo copyright Daniel J. Cox/Natural Exposures.

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