Hot Topics: Arctic - 2015 (pdf)

We present items that are either new or otherwise noteworthy and of potential interest to fisheries managers as Hot Topics.

Evaluating and ranking threats to the long-term persistence of polar bears

Polar bears (Ursus maritimus) were listed as globally threatened under the Endangered Species Act in 2008. This listing was primarily due to observed reductions in their sea ice habitat and the expectation that sea ice coverage will continue to decline in the future (USFWS, 2008). The diminishing sea ice coverage also increases polar bear exposure to other stressors related to in- creasing anthropogenic activity in the Arctic, such as petroleum extraction and shipping. A new report from the United States Geological Survey (USGS) indentified stressors affecting the long- term persistence of polar bears worldwide and evaluated the relative influence of these stressors (Atwood et al., 2015). Their study used a Bayesian network model which integrated environmental, ecological, and anthropogenic stressors.

Results indicate that the overall condition of sea ice and the availability of marine mammal prey had the most influence on the polar bear population outcomes. Stressors related to anthropogenic activity in the Arctic were much less influential to the population outcomes. The overall condition of sea ice and secondarily, the availability of marine mammal prey, were directly influenced by climate change. Polar bear population outcomes decreased by the end of the century under both stabilized and unabated greenhouse gas emissions. They concluded that minimizing the projected loss of sea ice habitat will be needed for the long-term persistence of polar bears, and will likely require stabilizing or reducing greenhouse gas emissions. Reducing the negative effects of anthropogenic activity on polar bears had a much smaller effect on polar bear population outcomes, but mitigating these human activities is more practical for resource managers to enact.

Contributed by Andy Whitehouse