The largest carnivores on land are getting squashed like tiny bugs. Measuring up to 10 feet tall (3 meters) and weighing in at up to 1,700 pounds (771 kilograms) polar bears are formidable creatures. But the massive animals are struggling with a global predator -- climate change -- and they're losing.
Scientists have been talking about melting polar ice caps and rising sea levels for decades. Now, it's not just talk. The average temperature in the Canadian Arctic has risen 7 degrees Farenheit (4 degrees Celsius) in the last 50 years [source: Daily Mail]. Temperatures in the Arctic Circle are increasing at twice the rate of the rest of the world's climate [source: Yahoo News]. The Arctic ice is melting, and the seas are becoming more treacherous. This is bad news for polar bears.
The polar bear habitat is about as frigid as it gets, and the animals are ideally suited to survive in the tough environment. They have several inches of both fur and blubber to insulate them from temperatures that drop to -49 Fahrenheit (-45 Celsius) in the dead of the Arctic winter. They've evolved to thrive under these conditions.
But what happens to a species when its ideal habitat starts to disappear? As we'll find out in the next section, it's not pretty at all.
Polar Bear Population on Thin Ice
With sea ice melting at record levels, polar bears face two massive, connected threats to their lives: an inability to access prey and an increasing distance between sea ice and land masses. Polar bears move to coastal regions when the weather warms up and the ice shrinks for the season. Because the bears aren't built to hunt on land, they mostly lie around as their bodies rely on stored-up fat for sustenance. When winter comes and the ice returns, it's time to hunt again.
The bears are strong swimmers and are skilled at hunting on the ice. The largest bears can swim 100 miles at a time [source: Daily Mail]. They're powerful animals, and they have thick layers of blubber that keep them warm in the water. But as the ice continues to melt, the time and energy it takes to swim from land to an ice sheet is increasing beyond the bears' capacity. Polar bears are being forced either to stay on land for extended periods without food or, when they get hungry enough, to make the swim and risk drowning or freezing along the way.
The other problem with having to hunt on increasingly shrinking bodies of ice is that the polar bears' main prey, the seal, is a stronger swimmer than the bears are. The bears are faster than seals on the ice, but with less ice to move across, the seals are getting away. And with less food to eat -- especially less fatty food like seals -- the polar bears are thinner than they used to be, and have less body fat to keep them warm. This lack of insulation makes the extended swim to and from shore even more dangerous, and it makes it harder to live comfortably for an extended period of time on land.
With their means of hunting and catching prey vastly diminished, and their blubber level shrinking, polar bears are wandering more and more into campsites and other areas where humans keep food out in the open. They're even Dumpster diving. It's a state of desperation, and none of the experts expect it to ease up.
How can the species survive under these conditions? On the next page, we'll see what the future holds for the world's dwindling polar bear population.
Polar Bear Extinction?
One of the world's 19 polar bear populations lives in Hudson Bay, Canada. In a Washington Post article, Dr. Ian Stirling of the Canadian Wildlife Service says that the ice sheets in that region are starting to crumble two and a half weeks earlier in the season than they did 30 years ago [source: Washington Post]. In the same article, the World Wildlife Fund's (WWF) lead scientist, Lara Hansen, predicts that dramatic weight loss and continued ice melt could make female polar bears in that region infertile by 2012. In an interview with the British Daily Mail, Stirling reports that female polar bears almost never give birth to more than one cub now. The possibility of extinction is very real [source: Daily Mail].
But scientists haven't given up on polar bears. An innovative program called Warm Waters for Cool Bears is trying a new approach to conserving the species. Typically, researchers have tracked the bears to see where they're living and where they're moving to better focus conservation efforts. But this approach isn't working well enough, or quickly enough. Warm Waters for Cool Bears tackles the problem from the other end -- tracking the habitats instead of the bears. Using several decades of satellite imagery and meteorological data, researchers with the Wildlife Conservation Society are trying to determine which polar ice caps have the best chance of surviving the warming trend. Efforts to save the polar bear populations living in those areas will then receive the greatest attention, since those conservation efforts are the most likely to succeed.
In 2007, The U.S. Fish and Wildlife Service filed a proposal to the U.S. government for polar bears to be classified as a threatened species under the Endangered Species Act. This would give the bears increased protection under the law. As of March 2008, the Bush administration has delayed its ruling. In the meantime, the U.S. Geological Survey predicts a loss of two-thirds of the current polar bear population by 2060 if melting trends continue.
Polar bears aren't the only ones in danger. Their prey is also being wiped out by global warming -- putting polar bears at greater risk of starving. The WWF announced in March 2008 that 1,500 newborn seals in the Arctic Circle are unlikely to survive their first few months. For about a month after they're born, seal cubs live burrowed in the ice as their bodies develop the fat layers that let them survive the frigid water. With the ice melting too quickly, many of the cubs will find themselves in the water before they're ready. Like the polar bear population, Arctic seal numbers have dwindled drastically in the last century, shrinking from 180,000 to about 8,500 [source: Yahoo News].
With both polar bears and seals dying from starvation and drowning in record numbers, the animal life at the Arctic Circle could be changed forever.
For more information on polar bears, baby seals and global warming, look over the links on the next page.
Related HowStuffWorks Articles
More Great Links
- Carlton, Jim. Is Global Warming Killing the Polar Bears? The Wall Street Journal. December 15, 2005. http://online.wsj.com/public/article_print/SB113452435089621905-vnekw47PQGtDyf3iv5XEN71_o5I_20061214.html
- Eilperin, Juliet. Study Says Polar Bears Could Face Extinction. The Washington Post. November 9, 2004. http://www.washingtonpost.com/wp-dyn/articles/A35233-2004Nov8.html
- Mouland, Bill. Global warming sees polar bears stranded on melting ice. The Daily Mail. February 1, 2007. http://www.dailymail.co.uk/pages/live/articles/news/news.html?in_article_ id=433170&in_page_id=1770
- Polar Bears and Global Warming. National Wildlife Federation. http://www.nwf.org/polarbearsandglobalwarming/
- Polar Bear Population Predicted To Dwindle With Retreating Ice. Science Daily. September 8, 2007. http://www.sciencedaily.com/releases/2007/09/070907224237.htm
- Seal cubs threatened by global warming, WWF warns. Yahoo! News (AFP). March 10, 2008. http://news.yahoo.com/s/afp/20080310/sc_afp/germanyclimatewarming
- US-Russia Polar Bear Treaty Ratified. ScienceDaily. October 18, 2007. http://www.sciencedaily.com/releases/2007/10/071014202952.htm
- Want To Save Polar Bears? Follow the Ice. ScienceDaily. June 1, 2007. http://www.sciencedaily.com/releases/2007/05/070531095420.htm