Polar Bears Are On A Sea Ice "Treadmill" That Is Speeding Up

Polar bears are declining due to a number of reasons, but primarily due to climate change melting the sea ice

Polar bears are declining due to a number of reasons, but primarily due to climate change melting the sea ice. Christopher Wood/Shutterstock

Polar bears off the coast of Alaska are effectively walking on a "sea ice treadmill" that is speeding up. This is piling more stress onto the animals that are already being impacted by climate change, making them expend more energy, and thus have to find more food to replenish it.

New research focused on the movement of sea ice across the Beaufort and Chukchi seas, as it drifts westward. The polar bears of the region, however, move in the opposite direction, and radio tags on female bears in the area relayed information about their movements. Combined with sea ice drift data, the team was able to calculate exactly how the bears are being affected by the changing environment.


“Increased sea ice drift rates likely exacerbate the physiological stress due to reduced foraging opportunity already experienced by many polar bears in the warming Arctic, adding yet another 'straw to the camel's back’,” explained George Durner, lead author of the paper published in Global Change Biology, in a statement.

The researchers found that the increase in the speed of the movement of ice meant that the bears were burning more calories. This equated to needing to catch 6 percent more seals per year, or roughly three whole seals. It may not sound like much, but with polar bears already struggling to get even the minimum number of seals needed, the extra stress and need for more food will only make the bears suffer further.

Despite many claims that polar bears are not suffering the impacts of climate change, this stance is simply not backed up by the science. Polar bears are divided up into many separate subpopulations, with different groups facing differing threats (such as hunting, tourism, or oil and gas exploration). But the one threat that is affecting them all is climate change.

This decline in sea ice has been directly linked to a fall in numbers of bears in some regions. But out of the 19 subpopulations of bears, there is only enough data for 10 of them to be properly assessed. Out of these, three are in decline, six are seemingly stable, and one is on the rise. But most of these are based on studies only looking at the last few decades, therefore not taking into account past numbers, and it is thought that one population in the rise is already starting from a much-reduced number in the first place.  


Whichever way you look at it, things are not looking good for polar bears, and are unlikely to improve. They are facing many threats on multiple levels, with one study finding that there is a 70 percent chance in the global population of bears falling by over a third within three generations.

  • tag
  • climate change,

  • energy,

  • global warming,

  • conservation,

  • polar bear,

  • sea ice,

  • calories,

  • ringed seal