In the tropical world, the polar bear has become the unofficial mascot of nature’s fall. We’ve all seen the images of these giant predators being reduced to skin and bones, clinging to ever-shrinking patches of sea ice as they try—and fail—to hunt. But in the Norwegian archipelago, a very different story unfolds.
Svalbard is home to about 3,000 people, and about the same number of bears are found in the Svalbard area and the Barents Sea. There are approximately 300 bears left in the archipelago throughout the year. Across the Arctic, shrinking sea ice is depriving the species of important hunting grounds, and Svalbard is no exception. But somehow, the polar bear population is thriving, with bears actually gaining weight since 2000 despite the rapid loss of sea ice.
The findings, published Thursday in the journal Scientific Reports, understandably surprised the study’s authors. Lead author Jon Aars, senior researcher at the Norwegian Polar Institute, told Ireland Live that when he joined the NPI in 2003, he would have expected the bears to be smaller and the population to decline by now.
“This paper highlights how polar bears can differ from each other, using Svalbard as an example during more than two decades of sea ice loss,” co-author Andrew Derocher, a professor of biology at the University of Alberta, told the advocacy group Polar Bears International.
To reduce the chances
Previous studies have shown that the average temperature in the Barents Sea region around Svalbard has increased by 3.6 degrees Fahrenheit (2 degrees Celsius) every decade since 1980. As a result, the area lost an average of four days of sea ice per year between 1979 and 2014, the study shows. That’s more than twice the rate of any other polar bear habitat, according to Aars and his colleagues.
Despite this, the number of polar bears in the Barents Sea has remained stable since the Aars census in 2004, which was estimated at 2,650 individuals across the region.
To investigate the drivers of this stability, the Aars team analyzed body composition data of 770 older polar bears measured in Svalbard between 1992 and 2019. The researchers then compared changes in the bears’ body composition index (BCI)—an index of stored fat—and the number of ice-free days in the Barents Sea region over a 27-year period.
They found that bears gained fat as sea ice continued to disappear, with their BCI rating increasing since 2000.
The challenges of a changing Arctic
The findings are puzzling in nature, but Aars and his colleagues have several theories as to how Svalbard’s bears are able to thrive despite rapid habitat loss.
One reason could be that many of the bears’ land-based predators, such as deer and walrus, are increasing after years of overexploitation by humans, the researchers suggest. These species may supplement the bears’ diet as hunting for marine animals—especially ringed seals—is less accessible.
However, it is also possible that the loss of sea ice causes ringed seals to congregate in small areas of sea ice, allowing bears to hunt more effectively. That said, the authors predict that this benefit will diminish with further reductions in sea ice, as the distances polar bears must travel to hunting grounds will increase. Researchers have already observed this phenomenon in other communities.
Unraveling the complexities that have allowed Svalbard’s bears to withstand the odds will require more research, according to the authors. For now, at least, this population is a testament to the fact that life often finds a way, but polar bears across the Arctic still face an existential threat.
