About This Species
The polar bear is the poster child for climate change for a reason. The bears meet two key criteria: they capture people's imaginations, and their lives are directly linked to climate change because they have evolved to exist on Arctic sea ice. Without sea ice, there are no polar bears.
Polar bears have evolved in specific ways that allow them to thrive through the brutal Arctic winter. They have black skin covered by translucent, hollow hair. The translucence allows the bears' hair to reflect light. The hollowness works as insulation, and makes them more buoyant in water. Their furry hind feet provide traction and warmth when padding across the ice. And they have webbed paws and dense leg bones, allowing them to swim long distances. These traits helped them earn their scientific name: Ursus maritimus, bear of the sea.
The skulls of polar bears are longer and narrower than other bears', which warms the air they inhale and helps them capture prey in tight spots, like birth lairs and breathing holes. Their favorite prey is seals—specifically ringed seals—though they are opportunistic feeders, meaning they will eat what they can catch. And as the Arctic's best predator, they can catch a lot.
Hunting on the sea ice allows polar bears access to the various creatures beneath it. One favorite hunting method: sitting beside a breathing hole in the ice, waiting for a seal to surface and grabbing it with its massive jaws.
In the lower regions of the Arctic, where sea ice melts during the summer, polar bears either follow the pack ice as it drifts north or they go ashore. While on shore, some scientists have observed polar bears eating goose eggs or caribou, or feasting on whale carcases. Unfortunately for the bears, studies have shown that the food they find on land does not match the calories they need, meaning the food they catch on the ice is irreplaceable.
Because the bears are so reliant on the ice for survival—and because the Arctic's sea ice is melting so rapidly due to climate change—the International Union for Conservation of Nature and Natural Resources has listed the species as "vulnerable" under the Endangered Species Act.
There are 19 subpopulations of polar bears, which are scattered across the Arctic. Of those, the IUCN lists three of the groups as in decline, six as stable and one as increasing. There is not enough data to classify the other groups.
The Arctic is warming faster than the rest of the world, and the sea ice is rapidly disappearing. NASA reports that it is dwindling at a rate of roughly 13 percent per decade since 1979, when satellites first began capturing sea ice levels. After 2016's particularly low levels, the National Snow and Ice Data Center reported that an area of ice about the size of Texas and Arizona combined was missing, when compared with the average from 1981-2010.
The final months of 2016 saw soaring temperatures in the Arctic, reaching about 9 degrees Fahrenheit above average throughout November and December. Around Christmas, that reached 50 degrees above the longterm average and the North Pole warmed above freezing, something that rarely happens outside of summer.
The Polar Bear's Shrinking Range
As goes the sea ice, so goes the polar bear—and it's not looking good for the sea ice.
A report released earlier this week by the U.S. Fish and Wildlife Service found that climate change is the biggest threat to polar bears, and that decisive action to address Arctic warming is the single most important element for polar bear survival.
Another report, published by a group of scientists in 2014 in the journal PLOS One, found that under business-as-usual climate projections, polar bears could face starvation and reproductive failure across the entire Canadian Arctic archipelago by the end of the century. Other studies have projected that by 2050, two-thirds of the polar bears could be gone.
Among the big problems for polar bears: they live a long time—around 15 years—and as many as two thirds of cubs don't survive. Species with longer lifespans do not adapt well to rapid habitat changes because those changes are not spread over multiple generations. One bear might see massive changes in its lifetime, which doesn't allow for adaptation necessary for survival.