Over the years, polar bears have become a symbol of the climate crisis and its impact on sea ice, which these animals depend on for survival. However, scientists haven’t been able to quantify how greenhouse gas emissions affect the survival rates of polar bears.
Fifteen years after polar bears were listed as a threatened species, a new study has made this possible by establishing a direct link.
A new report published in the journal Science shows that researchers can now calculate how human-caused greenhouse gas emissions negatively impact polar bears’ habitats and the percentage of cubs that will reach adulthood, an AFP report says.
One of the biggest roadblocks in establishing this link was the Bernhardt Memo, which prevented the inclusion of projects such as oil and gas drilling when evaluating the impact of climate change. Under the US Law, Endangered Species Act, agencies have to ensure projects they approve do not further harm listed species. However, a 2008 Department of Interior legal opinion stated greenhouse gas emissions didn't have to be considered because specific projects’ impact couldn't distinguished when examining all historic global emissions, according to the AFP report.
It is odd that polar bears were listed because of sea ice loss caused by global warming “but emissions have not been considered,” said lead author Steven C Amstrup, as reported by the Associated Press (AP).
There are 19 subpopulations of polar bears throughout the Arctic and they depend on sea ice to hunt for seals. When it melts, they have to either stay on land or swim for more time which affects their energy in finding food, thus risking their health. Human-caused global warming has led to there are fewer days of sea ice and longer fasting periods for polar bears, as reported by AP. According to scientists, most polar bears are on their way to becoming extent by the end of the century if global warming is not combated.
In the new study, the researchers quantified the number of ice-free, fasting days caused by a specific amount of human-caused greenhouse gas emission. “What's really relevant for policy is emissions," rather than atmospheric concentrations, said co-author Cecilia M. Bitz, as reported by AP.
The researchers calculated the link between how long polar bears fasted and each gigaton of cumulative emissions, which helped them calculate the impact of emissions from specific projects on future polar bear cub survival.
“It’s basically connecting the dots" from emissions to ice-free days to impacts on polar bears," Amstrup said in the AP report. According to the researchers, this method can be used to calculate similar survival rates for other species.
Melting sea ice has been one of the biggest causes of concerns regarding the climate crisis. Last week, a report revealed that thousands of emperor penguin chicks had drowned to death due to sea loss in Antarctica.