Study quantifies link between greenhouse gases, polar bear survival

Polar bears have long symbolized the dangers posed by climate change, as rising temperatures melt away the Arctic sea ice they depend upon for survival. Photo: AFPCub survival imperiledPolar bears rely heavily on the sea ice environment for hunting seals, traveling, mating and more. When sea ice melts in summer, they retreat onto land or unproductive ice far from the shore, where they endure long stretches of fasting. A landmark paper published in Nature in 2020 was the first to calculate links between changes in the sea ice caused by climate and polar bear demographics. "Amstrup and Bitz render an incontrovertible quantitative link among greenhouse gas emissions, sea ice decline, fasting duration -- a physiological response to lost hunting opportunities for seals -- and subsequent polar bear demographics," said Berger, who was not involved in the research.