Global warming and receding ice sheets threaten the lives of polar bears. But that’s not where the issues end. A new study published in Ecosphere established that the foraging range for polar bears in the Beaufort Sea area has increased by 64% between 1999 and 2016 compared to the period 1986-1998. The change is being driven by food scarcity.
The study was led by Anthony Pagano, a postdoctoral researcher at Washington State University. Pagano and his colleagues from the U.S. Geological Survey reviewed satellite data ranging from the 1980s and found that polar bears began moving further outside their range in search of food. Receding sea ice habitats pushed the bears north in search of food.
The continental shelf where polar bears feed has shallow water that contains plenty of fish and seals. As the world warms, the ice sheet that makes up the shelf melts off, leading to a food shortage for the bears. As a result, the animals have to travel further for food.
“Having to travel farther means these bears are expending more energy which can threaten their survival,” said Pagano. “If we want to preserve the habitat of these amazing mammals, then we need to focus on the root of the problem, which is slowing global climate change.”
Researchers say the continental sea ice continues to recede earlier and further each year. This forces polar bears to follow the sea ice to find food.
“The combined impact of having to move farther and farther north with the ice in the summer and then having to move back in the fall and winter as the ice freezes is taking a major toll,” Pagano said. “Our work highlights the worrying impact of sea ice decline on polar bear movement patterns.”
The study also found that about 20% of the polar bear population in the Beaufort Sea area avoids the traditional sea ice hunting grounds entirely. The bears prefer moving inland to feed on other foods such as carrion, berries, and even whale carcasses left on the shore by humans.
“Sometimes you’ll have 50 to 100 polar bears that congregate around these whale carcasses and compete with each other for food,” Pagano said. “As more and more bears move on land, I suspect there’ll be a lot more competition for these food resources and we’ll probably start seeing further decreases in abundance and survival.”
Lead image via Pixabay