Polar Bears - Threatened By Extinction Or Thriving Through Adaptation?

Polar bears are the image most people think of when Arctic sea ice loss is thought about. Many scientists such as Andrew Derocher from the University of Alberta believe that their numbers have fallen due to loss of sea ice over the last 50 years and in 2008 the United States classified polar bears as an endangered species. They are also classed as vulnerable by the IUCN Red List of Threatened Species. In 2010, Obbard et al. determined that 8 of 19 of the world’s polar bear populations are declining, 1 is increasing and 7 are unknown. Populations in the Southern Beaufort Sea have been reduced from around 1,800 bears in 1986 to 1,526 in 2006, possibly due to the reduction of sea ice.  

Figure 1: A graph by the IUCN illustrates the estimated number of polar bears existing. This shows a slight increase in numbers. However, this is only an estimate so may be inaccurate (source).

With the rate of sea ice decline at 13% per decade and December sea ice loss at 3.4% per decade, it is worrying to think how polar bears can survive without the ice they depend upon for hunting seals which is their main source of calories. Summers with reduced sea ice are getting longer every year, leaving most polar bears to fast without food for lengthier periods. Many polar bears are lean and starved at the end of a long summer with Cherry et al. in 2009 finding that two to three times as many polar bears were in a fasting state in 2005/2006 compared with 1985/1986. This indicates a drop in food opportunities due to reduced ice cover. Because of this, the number of cubs surviving into adulthood has fallen and body length and skull sizes have decreased. Due to a fall in seal hunt opportunities, bears are moving closer to human settlements such as Churchill in Canada to find food and are often shot when they come into human contact.

Figure 2: Can polar bears adapt to the ever changing cryosphere (source)?

Although sea ice has fallen, there are some signs that polar bears are adapting to less ice in the summer. Many are finding alternative food sources such as bird eggs, whale carcasses, caribou calves or human food waste, suggesting that it is not all doom and gloom for the polar bear. A few scientists like polar bear researcher Mitch Taylor believe that polar bear numbers are in fact rising rather than declining. The current scientific consensus places the worldwide polar bear population between 20,000 and 25,000 animals, more polar bears than existed prior to the 1973 International Agreement worldwide restriction on polar bear hunting. This is shown in figure 1. Polar bears in the Davis Straight at higher latitudes are thriving with sea ice still present but further south they appear to be struggling with a lack of ice to hunt on. I believe that at high latitudes the bears are surviving but at lower latitudes they need to be monitored consistently and regularly to ensure the health and survival of the species. Because of this regional variation, it is difficult to say if the polar bear species as a whole is thriving or if it is threatened by extinction. Instead of shooting bears that come into contact with humans they should be moved away from settlements which is done in Canadian towns like Churchill.

If polar bears move onto other food sources instead of starving and waiting for the seals in the winter, the species has a good chance of surviving in the future as ice dwindles in the Arctic.