The fate of the polar bear is inextricably linked to that of the sea ice on which they hunt. With the world warming, the prospects for these magnificent animals is balancing on a knife edge. 

“This is where it gets a little bit grim,” says Polar Bears International researcher Andrew Derocher, currently based in Churchill, Canada, to IFLScience. He explains how the loss of sea ice over the last 30 years has been well documented through satellite imagery, and the future isn’t particularly rosy either. “Going forward in time, there is a pretty consistent pattern for loss of sea ice. I think we’ve probably got enough global warming locked in that Churchill and the Hudson Bay system probably won’t have bears towards mid-century.”  

The survival of the polar bear and its continued persistence into the future effectively comes down to one thing: energetics. Can the bears put on enough weight to last them through the summer, or in the case of females, produce cubs? With the sea ice forming later and later in the year, it limits the amount of hunting the bears can do and the amount of weight they can gain to see them through the lean summer months. In fact, it’s estimated that during the ice-free season when the bears are not eating, they lose a kilogram of body mass per day.

^{The bears feed mainly on ringed and bearded seals, and usually feast only on the fat. Ondrej Prosicky/Shutterstock}

“Fat is what makes them tick,” says Derocher, who is also a professor at the University of Alberta. “They’re like a fat vacuum. It’s kind of like what I call the Oreo cookie effect. They open [the seal] up and they’re not interested in the outside, they’re not interested in the inside, they just want that icing layer which is the blubber. They just sort of scoop that out.” So adapted are they to eating and storing fat, they can eat up to 100 kilograms (220 pounds) of fat from a single seal, and out of that, 94 percent will go straight into the bears' own fat cells, unmodified. The bears might be facing other problems, such as females not having enough snow to nest in, but these are things they can adapt to. They can’t adapt to a disappearing hunting ground.

“It’s really no different than cutting down the Amazon forest, and people have no problem understanding that,” says Derocher. “People just don’t get that with sea ice.” This isn’t the only problem faced when trying to communicate the plight of the bears. The Arctic is what’s known as a “noisy” system, in that the bears have bad years, but they do also have good years. The overall trend, however, is firmly downwards. “And that downward trend is pretty darn strong.”

^{The fate of polar bears is inexplicably linked to the forming of the sea ice. Donland/Shutterstock} 

It might seem like the future for the bears is already set, one in which they no longer roam this world. But things can change; sea ice loss is not irreversible, and certain measures can be taken to protect the animals. One immediate action would be to stop all legal hunting of the bears in Canada and Alaska, though this would be contentious as the bears form an important part of native peoples' culture and subsistence.

Derocher can even envisage a time when conservationists will have to step in and give the bears a helping hand by provisioning the animals with enough food to keep them going until the sea ice forms again, and the bears can resume hunting. While this might sound dramatic, it's not unheard of, and not necessarily a bad thing. There is actually a long history of conservationists feeding wild animals, from Californian condors in America to brown bears in Eastern Europe.

This might help some local populations of polar bears cling on for a little longer, but it’s simply treating the symptom and not the cause. The real issue comes down to global action on climate change. “The big question is can we do something, such as at the [climate talks in Paris] that will allow us to hold onto polar bears in the very high reaches of the Arctic?” These populations have a good chance of surviving to the end of the century, and if we’re able to get our act together and curb our emissions, the bears will come back if it gets cold again.

As a continuing part of Polar Bear Week, you can watch the bears live from the tundra, over at explore.org. 

^{A female bear and her cub waiting out the summer for the ice to form in Hudson Bay. BJ Kirschhoffer/Polar Bears International}