Fifteen years after polar bears were listed as threatened, a new study says researchers have overcome a roadblock in the Endangered Species Act that prevented the federal government from considering climate change when evaluating impacts of projects such as oil and gas drilling.
The act requires agencies to ensure projects they approve don’t further harm listed species. But a 2008 Department of Interior legal opinion said greenhouse gas emissions didn’t have to be considered because the impact from specific projects couldn’t be distinguished from that of all historic global emissions. says scientists for the first time are able to directly quantify the impact of human-caused greenhouse gas emissions from specific sources on polar bear cub survival.
“What’s really relevant for policy is emissions,” rather than atmospheric concentrations, said co-author Cecilia M. Bitz, a climatologist and director of the climate change program at the University of Washington. But the lack of consistent estimates of population trends and survival rates for some polar bear subpopulations, which are distributed over a very large geographic area with differences in sea ice and food sources, can be “problematic when you’re trying to to match for recent greenhouse gas emission trajectories with population survival rates,” he said.
“I think it takes us a little bit closer to understanding some of those relationships, but ... I just don’t know that this paper pushes it over a new threshold,” said Andrew Derocher, a polar bear expert and biological sciences professor at the University of Alberta, who believes polar bears are at risk of extinction long-term. “I just don’t think that this is the smoking gun that is going to change opinion.
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