Scientists expected the opposite, but polar bears in the Norwegian Arctic archipelago of Svalbard have become fatter and healthier since the early 1990s, all while sea ice has steadily declined due to climate change.
Polar bears rely on sea ice as a platform from which to hunt the seals that they rely on for blubber-rich meals. The bears' fat reserves provide energy and insulation and allow mothers to produce rich milk for cubs.
Researchers weighed and measured 770 adults in Svalbard between 1992 and 2019 and found that bears had become significantly fatter.
They think that Svalbard bears have adapted to recent ice loss by eating more land-based prey, including reindeer and walruses.
The discovery, published in Scientific Reports, was particularly puzzling because of the impact of climate change in Svalbard. During the same period, global temperature rises have reduced the number of ice-free days per year in the region by almost 100 - at a rate of about four days each year.
Dr. Jon Aars from the Norwegian Polar Institute explained that the fatter a bear is the better it is, despite expecting a decline in body conditions due to profound sea ice loss.
While this is unexpected good news, the researchers warn that it is unlikely to be sustainable. As sea ice continues to decline, bears will have to travel further to access hunting grounds, using more energy and depleting precious fat reserves. Moreover, experts suggest that the increase in walrus populations and the recovery from historical hunting pressures may have temporarily benefitted these Svalbard bears.
Nonetheless, the long-term outlook remains concerning; ice loss will ultimately lead to declines in polar bear populations, emphasizing the urgent need for continued conservation efforts.
