Climate change is doing more than just heating up the planet. It’s also making polar bears, a species that has been referred to as climate refugees, a lot more aggressive and, in turn, leading to a rise in attacks from the carnivorous animal. New Scientist reported that polar bears have an increased likelihood of being aggressive and clashing with humans in areas where the two cohabit.
“You’ve got this perfect storm set up where you’ve got bears that are spending increasing amounts of time on land becoming nutritionally stressed, moving into areas of human settlements,” Todd Atwood, a wildlife biologist at the U.S. Geological Survey, told New Scientist.
Atwood and a team explored this link in a new study by diving into almost 150 years of records of bear attacks in five coastal areas: Canada, Greenland, Russia, the U.S. and Norway. The team gathered the data from an array of sources like government agencies, biologists’ field notes, news reports and logs from ships. (The authors noted that there are likely some attacks that have not been reported and they may not have access to every logged attack.)
Their findings show a clear trend. From 1870 to 2014, there were 73 cases of polar bears attacking an individual or a group of people. Cumulatively, the 73 cases left 63 injured and 20 dead. In most cases, a male bear was involved and the attack was predatory — wounds to the head or neck and consumption of human flesh.
The team then scored each attack, based on available details, on the bear’s body condition. The scale was one (skinny) to five (obese) and based on the body condition index developed for polar bears. Turns out 61% of the bears were “below average” which occurs when these bears don’t find enough food. Likely because of diminishing sea ice, which is their “habitual seal hunting ground.”
There’s also a difference in the timeline. On average, there have been eight to nine polar bear attacks per decade. But from 2010 to 2014 — half a decade — there were 15. According to Atwood, this spike leads one to theorize that “around 2000 we might have hit a shift in the kind of conditions in the Arctic.”
Climate change is altering the landscape of the environment and one outcome of high global greenhouse gas emissions is melting sea ice. Experts have found arctic sea ice extent and thickness to have dwindled over the past 40 years. Some have even projected that the Arctic Ocean may be ice free in the summer by as early as 2020.
For polar bears, sea ice gives them contact with their meals — ice seals — and a terrestrial habitat roadblocks their access to prey. And shorter winter and longer summers means the polar bears have a smaller hunting season, requiring them to survive off their stored body fat. The increased fasting and nutritional stress has been linked to “infanticide, cannibalism and starvation in some polar bear subpopulations,” according to the study.
The link between polar bear and climate change was brought to mainstream attention in Al Gore’s film, An Inconvenient Truth. In 2008, the government listed polar bears, the largest of all bear species, as a threatened specimen under the Endangered Species Act. According to an International Union for Conservation of Nature’s Red List assessment in 2015, a more than 30% decline in polar bear population has been forecasted by 2050.
“Historical conditions are increasingly rare as the availability of sea ice is dramatically and rapidly changing throughout the polar bear range,” the authors of the study wrote. “These changes will likely influence how polar bears interact with people. For example, the greatest number of polar bear attacks occurred in the partial decade of 2010–2014, which was characterized by historically low summer sea ice extent and long ice-free periods ... that have been linked to increased land use in a number of subpopulations.”