Plummeting polar bear numbers directly linked to greenhouse gas emissions for first time

SEATTLE — For the first time, scientists have established a direct link between declining polar bear populations and greenhouse gas emissions.

“This breakthrough will allow for enhanced legal protection for this iconic species,” researchers from the University of Washington assert.

The team, in collaboration with United States-based conservation group Polar Bears International, conducted the study. Published in the journal Science, the research builds on previous work while offering new analysis, thus providing a measurable connection between greenhouse gases and polar bear survival rates.

According to the research team, a warming Arctic restricts polar bears’ access to sea ice, their primary hunting ground. In the absence of ice during summer months, the bears are forced to fast. In extreme scenarios, adult bears could die, but even before reaching that point, they lose the capability to successfully raise cubs.

“Until now, scientists hadn’t offered the quantitative evidence to relate greenhouse gas emissions to population decline,” says Professor Cecilia Bitz of the University of Washington, the study’s second author, in a university release.

Bitz’s data analysis revealed that cumulative greenhouse gas emissions largely explain the recent downward trends in some polar bear subpopulations, such as those in western Hudson Bay.

“I hope the U.S. government fulfills its legal obligation to protect polar bears by limiting greenhouse gas emissions from human activity,” Bitz continues. “I hope investments are made into fossil fuel alternatives that exist today, and to discover new technologies that avoid greenhouse gas emissions.”

Polar bears were the first species to be listed under the Endangered Species Act in 2008 due to the threat of climate change. Scientists had clear biological evidence that warming could lead to the disappearance of up to two-thirds of the world’s polar bear population by 2050.

The Endangered Species Act mandates that any government-authorized projects, including oil and gas leases, must not further endanger any listed species. However, a 2008 document from the U.S. Department of the Interior, known as the Bernhardt Opinion, required specific proof connecting a proposed project’s greenhouse gas emissions to a species’ survival before full protections could be implemented.

“In this paper, we reveal a direct link between anthropogenic greenhouse gas emissions and cub survival rates,” says Professor Steven Amstrup, the study’s lead author and chief scientist emeritus at Polar Bears International.

The paper suggests that greenhouse gas emissions from hundreds of U.S. power plants could, for example, reduce polar bear cub survival rates in the southern Beaufort Sea by around four percent over 30 years.

“Overcoming the challenge of the Bernhardt Opinion is absolutely in the realm of climate research,” Prof. Bitz says. “Our study shows that not only sea ice, but polar bear survival, can be directly related to our greenhouse gas emissions.”

The research team believes their methodology could be adapted for other species and habitats directly affected by global warming, including coral reefs and beach-nesting species impacted by rising sea levels.

“Polar bears are beautiful creatures, and I hope they survive global warming,” concludes Prof. Bitz. “However, the health and well-being of humans, especially the most vulnerable, is of the utmost importance. Everything governments and industries can do to reduce greenhouse gas emissions matters, and will help avoid the worst consequences.”

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South West News Service writer Stephen Beech contributed to this report.