Will These Be the Last Polar Bears on Earth?
A newly identified population in Greenland is less dependent on the vanishing sea ice. But even they can’t hold out forever.
The last surviving member of a species—the individual whose death brings extinction—is called an endling. Those individuals can sometimes be identified, even named. Many more of them live and die unseen. For example, archaeological evidence shows that the woolly mammoth endling lived about 4,000 years ago on Wrangel Island, 87 miles off the coast of Siberia. Mammoths survived there for millennia after the rest of their kind were wiped out by changing climate and human hunters. But eventually, through some combination of factors, including extreme weather events and harmful mutations acquired through heavy inbreeding, they also perished. I thought about them as I listened to Kristin Laidre talking about polar bears.
Laidre, who is an ecologist at the University of Washington, has identified a unique group of polar bears that lives in Greenland’s southeastern tip. Genetically isolated from other populations, the bears’ habits make them less dependent on sea ice—the floating, frozen platforms on which most polar bears hunt, travel, and raise their young. As sea ice disappears, so do the polar bears’ odds of survival. Those in Southeast Greenland seem better suited to a warming world, and could persist while the rest of the Arctic becomes uninhabitable.
“Does this mean polar bears are saved?” Laidre told me. “It doesn’t.” Like the Wrangel mammoths, they might outlast others of their kind, but they won’t hold out forever. Perhaps Southeast Greenland is simply the place where the polar-bear endling will live out its species’ final days.
About 26,000 polar bears are left in the wild, divided into 19 subpopulations that live in different corners of the Arctic. One of these subpopulations lives along 2,000 miles of mostly uninhabited coastline in East Greenland, and had never been properly studied. In 2011, Laidre and her colleagues began a decade-long effort to count these bears so the Greenland government could set conservation goals and subsistence-hunting quotas. Following talks with local subsistence hunters, the team began systematically working its way along the coast.
The researchers hit Southeast Greenland in 2015, mostly to be thorough. A very fast current rips down Greenland’s eastern flank, filling the southeast with small and sparsely packed ice floes—“a difficult landscape for a polar bear to use,” Laidre told me. She and her colleagues guessed that some bears might live in the region’s fjords, but “I remember flying into one and expecting not to see very much,” Laidre said. “Within 10 minutes, we saw six bears all within a few kilometers of each other.” On a normal bear-spotting flight, she’d expect to see one every hour or so. What were so many polar bears doing in a place that should be mostly bear-free?
That first trip was short-lived, but Laidre knew she had to go back, even though Southeast Greenland has volatile weather, a harsh coastline, almost no human settlements, and no spots for fuel or food. To work there, the researchers buried barrels of fuel along the snowy coastline, creating makeshift depots that a helicopter could hopscotch between. When they found polar bears, they’d tranquilize them from the moving helicopter, collect physical measurements and tissue samples, and (if the bear was an adult female) fit a tracking collar.
Usually, the team commuted from a base two hours away. But one evening, the scientists decided to sleep in an abandoned mining camp, with the aim of starting the next day nearer the animals. They got their wish: That night, Laidre heard the sound of large paws treading on squeaky snow, and woke to find … a polar bear running off with her bag of polar-bear-tissue samples. She exited the camp, pursuing the bear while banging a metal spoon against a frying pan. It dropped the precious bag and fled. “Then we realized it also had taken a few bites of our helicopter,” she told me.
From the hard-won data, the team realized that “these are seriously local bears,” Laidre said. Although polar bears usually roam over large distances, those in Southeast Greenland stay in the same fjord for years. Even when they accidentally got caught in the rapid eastern current and were swept off to the south, they’d just swim to shore and trundle back to the same fjord they started from. Their homebody instincts are so strong that they never interact with bears that live further up the coast. It’s as if an invisible wall at 64 degrees north separates the southeast bears from their northeast cousins.
The bears’ DNA told the same story. “Polar bears are remarkably genetically similar to each other,” Beth Shapiro, an evolutionary biologist at UC Santa Cruz, told me. But the Southeast Greenland bears are so distinct from the 19 known subpopulations that when Shapiro’s team first analyzed the samples that Laidre had collected, “we thought we’d done something wrong,” she said. These are the most genetically isolated polar bears in the world—a 20th subpopulation that’s been mostly self-contained in a corner of Greenland for a few hundred years, and possibly longer.
Like all other polar bears, those in Southeast Greenland use sea ice as platforms from which they hunt seals. That ice is available for only about 100 days of the year, which isn’t enough. But at other times, the bears can survive because of the unusual landscape they inhabit: In lieu of sea ice, they use freshwater icebergs that are funneled into the fjord by a glacier. This “glacial mélange” is the secret of their survival, at least for now. In other parts of the Arctic, polar bears might enjoy almost twice as many ice-covered days in a year, but they’re still faring poorly “because once that ice is gone, they don’t have access to an alternative,” Laidre said.
The Southeast Greenland polar bears are “bears of the future,” Laidre added. As the Arctic warms, the number of ice-free days will increase, and more polar bears will experience the same conditions that their Southeast Greenland counterparts currently face. Most won’t have a glacial backup, and will die. If carbon emissions continue along their current course, nearly all of the subpopulations will likely be wiped out by the end of this century. The Southeast Greenland subpopulation is “an example of what may happen in a warming Arctic, as the bears persist in smaller groups in smaller areas at the fringes of their range, and become progressively more isolated, with increasing inbreeding over time,” Andrew Derocher, a polar-bear researcher at the University of Alberta, told me.
“This shouldn’t be spun as ‘Somehow, glaciers will save polar bears,’” Laidre said. Most populations don’t have access to glacier fronts, and besides, glaciers “are in retreat essentially everywhere in Greenland,” John Whiteman, the chief research scientist at Polar Bears International, told me. That’s one reason “it’s highly unlikely,” Derocher said, that even the Southeast Greenland bears will “persist far into the future with the warming that is predicted.” There also aren’t enough of them to sustain a thriving population, and their birth rates are already worryingly low. Inbreeding might eventually riddle them with genetic problems.
“I don’t think it’s totally hopeless for polar bears, but we need strong action to limit human-caused climate change if we want to save them,” Laidre said. Otherwise, the Southeast Greenland population could be the modern equivalent of the Wrangel Island mammoths—the last survivors of a world that no longer has a place for them.