Synergy Effect May Increase Threat to Polar Bears
On the frozen surface of the Barents Sea, tucked away between mainland Norway, Svalbard and Russia, polar bears are actually doing well. But their good fortune might not last, researcher says.
Ever since Norway did away with hunting in the early 1970s, the regional population of polar bears has grown in spite of a decrease in sea ice cover and high levels of environmental toxins such as PCBs. This is according to Jon Aars, a polar bear expert and senior researcher at the Norwegian Polar Institute.
Now, however, the polar bear population may have gained all it can from the ban on hunting. And researchers fear that a combination of toxins and a decrease in ice extent may add up to worse than the sum of their parts. There is reason to believe that an unfortunate synergy effect may arise as the Earth gets warmer, Aars said in a recent interview from his office telephone in Tromsø in northern Norway.
“Today we see polar bears growing skinnier,” Aars said. As they burn more fat they will be less resistant to illnesses, and they will also absorb more toxins into their bloodstream. “It is likely that such a synergy effect will happen.”
Polar bears depend on sea ice as a platform for hunting seals and small whales—a vital diet for maintaining their fat reserves. But as the Arctic has become warmer due to climate change, Arctic sea ice has been shrinking in extent.
According to the National Snow and Ice Data Center, or NSIDC, at the University of Colorado, the extent in Arctic sea ice has decreased by 11.5% per decade since satellites started recording the development in 1979. Moreover, since the Barents Sea is one of the areas in the world that seems to follow climate models the closest, polar bears here may be particularly exposed to starvation as the Earth continues to warm.
“In the latest years we have had very little ice. It has always varied, which is natural, but the last years have been completely catastrophic,” Aars said referring to the Barents Sea area.
Today, figuring out more precisely how environmental toxins affect bears is therefore critical for finding ways to help them survive as sea ice continues to decrease.
“What we still don’t know is how much pollution affects survival and reproduction in the polar bear,” Aars said. “We know that levels are high, and we know from other species that pollutants can affect reproduction… But it is not easy to say how big those effects will be.”
According to Aars, there is no doubt that the polar bear is headed in the wrong direction. Now the challenge is to understand the details. By definition, climate models provide imperfect information about the future. And polar bears are affected by climate changes differently in different regions of the world. As a result, it is difficult to formulate proactive preservation strategies for the polar bear, he said.
“The first move is to know as many pieces of the puzzle as possible. That way we can deal with new situations as they arise,” Aars said. He adds that biologists know a lot about how polar bears move on ice, but they still need to learn how long they can swim and for how long they can stay in the water.
“As populations become smaller in the future—for example in isolated populations on Svalbard and Greenland—it will be important to know how far they can swim to see if they can exchange genetics between them.”
Climate change is the single biggest threat to polar bears, according to Aars. It happens on a global scale, and though it affects different populations differently, it affects them all.