New research suggests that capping global warming below 2 degrees Celsius would lower chances of big population decline by preserving critical sea ice
Now that the world has a clear target for limiting global warming, scientists say they show how how achieving the goal would protect at least some ecosystems and vulnerable species from impacts.
One newly updated study found that aggressively cutting greenhouse gas emissions would help ensure the survival of polar bears, listed as threatened because of Arctic sea ice declines. Polar bears depend on the ice as platforms for feeding around the biologically rich continental shelves of the Arctic Ocean.
Another recent study found that polar bears are already running out of food options. The research showed that the bears are increasingly using more and more energy trying to find food, essentially depleting their nutritional bank account. other genetic studies show how the bears are ranging farther north, chasing sea ice.
“The polar bear’s recent directional gene flow northward is something new,” said Elizabeth Peacock, USGS researcher and lead author of the study. “In our analyses that focused on more historic gene flow, we did not detect movement in this direction.”
Sea ice loss is also affecting polar bears in more subtle ways, according to scientists who track what they eat. A shift in diet means the bears are ingesting more toxic chemicals, with as-yet unknown biological consequences.
Climate projections and biological models suggest that, if atmospheric greenhouse gas concentrations increase at the current rate, polar bear populations will plummet by the end of the century. But stabilizing emissions by 2050 would slow the drop by about 25 percent in two of the four ecoregions where the bears live.
If global warming can be capped below 2 degrees Celsius, it would cut the chances of significant reductions in all polar bear populations by 25, according to the researchers, who published their findings in the journal Ecosphere.
In a press release, U.S. Geological Survey researcher Todd Atwood said, “The scenarios predicted by our models are encouraging in that there are clear actions that humans can take to improve the chances that healthy polar bear populations persist in the future. The research can help management officials and political leaders make decisions based on the best available science,” he said.
The research showed that minimizing other population stressors such as hunting, trans-Arctic shipping, oil and gas exploration and exposure to contaminants had comparatively minor effects on polar bear outcomes in the long term.
In 2013, the USFWS convened the Polar Bear Recovery Team to draft a recovery plan for polar bears. To inform that effort, the USGS developed a model that included projections of future sea ice conditions to evaluate the influence of different threats to polar bear population persistence and thus provide a framework for recovery planning.
Results of that modeling effort were published in 2015 to coincide with the accelerated timeline for developing the polar bear recovery greenhouse gas emission trajectories.