Polar bears are getting fatter in the fastest-warming place on Earth

Polar bears have been getting fatter even as sea ice disappears in Norway’s Svalbard archipelago, the fastest-warming place on Earth – but scientists don’t expect the good times to last.

The northern Barents Sea, which stretches between Svalbard and Russia’s Novaya Zemlya in the Arctic Ocean, has been heating up seven times faster than the globe as a whole. The sea ice around Svalbard lasts two months less in winter and spring than it did two decades ago. Bears now have to swim 200 to 300 kilometres between hunting grounds on the ice and snow dens on the islands where they give birth.

But the average size and weight of the Svalbard bears have increased since 2000, a finding that surprised Jon Aars at the Norwegian Polar Institute, who led the study.

“We should think about this as good news for Svalbard,” he says. “But if you want bad news, you can just go and look somewhere else where you have very, very firm evidence that climate change is impacting polar bears negatively.”

This wide-ranging, solitary predator is split into 20 populations across the far north, where it is extremely difficult to count. While its numbers are declining in parts of Alaska, Canada and Greenland, they appear to be stable or increasing in other places. For nine of the populations, data is too sparse to say.

The Barents Sea population, which was estimated at 1900 to 3600 bears two decades ago, is thought to be stable or perhaps even growing. Starting in 1995, Aars and his colleagues tranquilised 770 bears with dart guns from helicopters. They hopped out onto the snow or ice to measure their length and, to estimate weight, their girth at the chest.

Trend analysis showed this body condition decreased until 2000, then increased until the end of observations in 2019.

In the spring, when ringed seals give birth to pups on the sea ice, polar bears hunt them to build up stores of fat for the ice-free months. Aars and his colleagues believe the shrinking ice area may be making these seals easier to find.

The bears are also exploiting new food sources. The approximately 250 individuals that remain on the islands when the ice recedes may be hunting more bearded seals along the coast, as well as harbour seals, which are spreading to Svalbard as the climate warms.

These “local bears” are increasingly ransacking duck and geese colonies for eggs, and they have been seen chasing down reindeer from a growing cervid population. The carcasses of walruses, another species that is increasing there, can provide weeks of feasting.

Svalbard bears are better able to adapt than scientists expected, “so extinction is delayed”, says Jouke Prop at the University of Groningen in the Netherlands.

“It’s a species in despair. They’re doing crazy things,” he says. “It doesn’t work everywhere, but it may work for some time” on Svalbard.

Polar bears may still not have reached the archipelago’s carrying capacity after Arctic nations banned hunting them for hides and zoo specimens in 1973. But warming is beginning to disrupt the food chain, which starts with algae on the underside of sea ice, warns Prop.

“It will be very difficult to support a reasonable population of polar bears if sea ice disappears,” he says.

“There will be a threshold, and… polar bears in Svalbard will be negatively affected by continued sea ice loss,” Aars says.

The northern lights, fjords and glaciers: Svalbard and Tromso, Norway

Join a thrilling Arctic adventure in Norway, where you can delve into the science behind the northern lights, Arctic ecosystems and human adaptation to extreme northern environments.