The Science on Polar Bears

A witness to polar bears' plight, photographer and writer Jenny Ross, shares photos and explains what recent scientific studies are finding on the effects of climate change on polar bears.

polar bear familyIt is not often that I read something as clear and compelling as the recent article on polar bears in the Arctic by nature photographer Jenny Ross, whose photographs bring to life the struggle polar bears face as the Arctic warms.

The thing about this article, which makes it worth sitting down and losing yourself in her story and photographs, is the clear and detailed description of how polar bears' lives are intertwined with Arctic ice. Ross explains:

Due to their compulsory connections with sea ice for every crucial facet of life, polar bears are exceedingly vulnerable to the effects of climate warming.

Polar bear's dependence on sea ice is clear when you consider that their main source of food is ringed seals, a species that itself depends on sea ice to survive. All of polar bears' methods of catching seals depend on sea ice--they wait motionless by seals’ breathing holes in the ice until a seal returns or slowly stalk up to a seal resting on the sea-ice surface. Yet, as the ice disappears earler in the spring and forms later in the fall, polar bears cannot switch to other food sources because they require tremendous amounts of energy from the high-fat seals to stay warm.  

Struggles for Polar Bears as Ice Melts

Ross has spent time observing polar bears in the wild, and gives a first-hand account of watching individual polar bears swimming in the open ocean hundreds of miles from the nearest sea ice--in an area of the Arctic that only a few decades earlier were covered in ice year round.  These types of long swims are becoming more common as the ice retreats, yet can be deadly for polar bears and their cubs.

In addition to overly-long swims to find retreating sea ice, ice-free periods in the summer are becoming longer in southern areas of their range.

Research by Stirling and colleagues has established that during the past few decades, due to climate warming, the sea ice on Hudson Bay has been breaking up progressively earlier in the summer. Break-up now occurs at least four weeks earlier than it did a few decades ago. Consequently, the WHB [Western Hudson Bay] bears have much less time on the ice to hunt seals and accumulate the fat necessary to survive the ice-free period. Furthermore, explains Stirling, in addition to coming ashore with meager quantities of stored fat, "the bears are now being forced to fast for even longer periods because freeze-up is coming progressively later in the fall as well.”

Read more on how polar bears' lives are changing in the southern areas of the Arctic--and what the science is telling us about their future.

Research on the Future of Polar Bears

Right now, there are approximately 20,000 polar bears living in 19 relatively separate populations, but scientists determined that 8 of the 19 populations are already declining due to global warming. If temperatures continue to rise unchecked, scientists expect at least two-thirds of the world's polar bears will disappear within the next 40 years.  But, all is not lost for polar bears living further north in the Arctic. Polar bear researcher Dr. Ian Amstrup explains:

"There's a widely held perception that nothing can be done to help polar bears and the arctic ecosystem," says Amstrup. "Our new findings show this isn't true. Saving polar bears is all about temperature and sea ice. By minimizing greenhouse-gas emissions and therefore temperature rise, we will retain more sea ice. The more sea-ice habitat we retain, the more polar bears will survive."

Join the fight for the future of polar bears--donate to the National Wildlife Federation Action Fund to continue the campaign in 2012 to limit global warming pollution.