A lonely polar bear swimming for hours in an ice-free Arctic has been a poster child of a warming world affecting wildlife.
But north of Norway, the Barents Sea bears are doing alright — for now.
Decades of melting sea ice and increasingly ice-free days in the region have not had the expected health impacts on this specific polar bear subpopulation, according to new research published in Scientific Reports.
“The bears are doing OK there,” said co-author Andrew Derocher, biological sciences professor at the University of Alberta. “That might seem a bit counterintuitive … until you look at the ecosystem as a whole.”
The bears are seemingly adjusting to the lack of sea ice and still able to eat what they need to survive.
In a species so iconically tied to the change humans are causing to the climate, experts see a reminder of variation within populations.
“We know that there will be some winners in climate change. We hear a lot about the losers,” said Marie Auger-Méthé, statistical ecologist with the University of British Columbia, who was not involved in the study. “There’s some animals that will take advantage of the conditions that are opening up for them.”
At the same time, experts warn this adaptation may be temporary, and further loss of sea ice will still be devastating for polar bears.
Hundreds of live captures
The new research uses data from live captures of bears between 1995 and 2019 in the Svalbard archipelago, halfway between Norway and the North Pole, an archipelago in the Arctic Ocean and the Barents Sea.
This group, one of 20 recognized subpopulations of polar bears, is made up of bears that stay on land during ice-free periods and bears that go roaming as far as Russia’s Franz Josef Land.
In total, 770 bears were studied through capture-mark-and-recapture expeditions, which involve chasing these bears with helicopters.
“So you fly around, you find the bear, you dart it, it goes down flat,” Jon Aars, lead author and senior scientist at the Norwegian Polar Institute, told CBC News from Longyearbyen in Svalbard.
Height, girth and other measurements are taken to get a sense of body condition, which Aars calls a simple proxy for how much fat is on the bear. This can help indicate a health concern before any population declines.
“It gives us a sense [if] there’s a problem,” Auger-Méthé explained, “and then we can act at a time scale that’s relevant for conservation.”
As that data was gathered over decades, the effects of a warming Arctic were profound. After 2005, polar bears in the Svalbard area would have to deal with sea ice breaking up a month earlier than usual and have to navigate an additional hundred days, on average, of ice-free conditions.
Yet despite an initial decline, their body conditions have rebounded and stabilized.
“It is surprising that they don’t lose weight or that they do so well despite that we know that they have much, much less time on the sea ice,” said Aars.
Diversifying the menu
Part of what experts think explains this lack of body condition decline is the consumption of prey that isn’t normally part of the polar bear diet — and is potentially easier for them to access.
“There’s the possibility that there might be unusually rich alternative foods to their standard ringed seal/bearded seal diet in the area,” suggested John Whiteman, chief research scientist with Polar Bears International, who was not involved in the research.
Aars and Derocher point to the availability of walruses, which have rebounded in population since being protected from hunting in 1952. Polar bears also eat bird eggs and whale carcasses.
“I actually have been flying at the moment where you see a polar bear kill a reindeer,” Aars said. Beyond that, the on-the-ground availability of these other prey species — which don’t hang out on sea ice — mean polar bears don’t need to expend as much energy travelling to hunt.
In a rare occurrence, a polar bear in Churchill is taking care of her offspring and another cub that is not her own. Evan Richardson, a polar bear research scientist with Environment and Climate Change Canada, is studying the family.
Climate change still a threat
Experts are cautiously optimistic about these particular polar bears but do not see that success translating across all populations.
“For Canadian polar bears, this doesn’t change anything. Our bears are not doing well,” Auger-Méthé says, adding that extensive research has studied the bears in the western Hudson Bay.
“It’s clear that their body condition, their survival, their reproduction has been declining with sea ice, and the same is true in the Beaufort Sea.”
They’re all the same species but Whiteman sees the short-term future for polar bears differing from region to region. Ironically, he says, their long-term future is clearer, as the world warms from humanity’s greenhouse gases.
“At some point, you lose so much sea ice that you just lose the polar bears. And there isn’t a way around that.”
Whether these Barents Sea bears survive to the end of the century, says Derocher, is a wild card.
“But I’ve been surprised more than once studying polar bears over the last 40 years.”
