The polar bear (Ursus maritimus), is actually a marine mammal that spends most of its time in the sea than on land. Although it is on the Arctic ice that the polar bears are making their living, and that is why global warming is such a serious threat. As climate change melts sea ice, the Geological Survey projects that two thirds of polar bears will disappear by 2050. For polar bears the sea ice is so important, because of this loss of ice it means; reduced access to food, drop in body condition, lower cub survival rates, increase drowning, increase in cannibalism, and loss of access to denning areas.
In just 20 years the ice free period in Hudson Bay has has increased by an average of 20 days, cutting short polar bears’ seal hunting season by nearly three weeks. The ice is freezing later in the fall, but it is the earlier spring ice melt that is especially difficult for the bears. They have a narrower timeframe in which to hunt during the critical season when seal pups are born. As a result, average bear weight has dropped by 15 percent, causing reproduction rates to decline.
The retreating sea ice platforms have also been a problem. They have been further away from land which means more swimming for the polar bears and rougher wave conditions, making it more hazardous. In 2004 a biologist in Beaufort Sea found some drowned polar bears because of this condition. They estimated that there were actually more drowned bears than what was actually found.
The shrinking ice caps reduce access to one of the polar bears main hunting source: seals. The reduction in the caps affects the near protected areas for the fish that the seas eat which affect the seals nutritional status as well as their reproductive rates. The result of this is that the polar bears are going hungry for longer periods of time, which can cause cannibalistic behavior.
In 2008, the polar bear was listed as threatened under the Endangered Species Act primarily because of the decline in of their main habitat, sea ice.
Although recently, there have been studies showing that polar bears are actually increasing in numbers. As you can see in the graph below, the polar bears population is estimated to be around 26,000 as confirmed by the IUCN Red List in November of 2015.
The following qualifier also stated:
Because the global population estimate range includes subpopulation estimates of variable quality it is not used as a monitoring benchmark or other status assessment tool. Rather, it simply expresses a reasonable range in numbers, based on a combination of the best available information and understandings of polar bear habitat. Conservation assessments focus on the trends in subpopulations for which statistical estimates are available. Some of those subpopulations are declining, others are stable, and some may be increasing.
The IUCN don’t want anyone to assume that the global polar bear population estimate is accurate enough to track changes in abundance over time – if it goes up a bit, it means nothing, and if it goes down a bit, it also means nothing. They think the number “25,000” implies less accuracy than does “26,000” – so that’s the number they prefer to use.
There are considered to be about 20,000-32,000 polar bears worldwide, which is valuable information to us so that we can keep on monitoring their population numbers. These numbers are a lot higher than other endangered species such as the snow leopards which are estimated to be around 6,000.
“Global Warming and Polar Bears – National Wildlife Federation.” Global Warming and Polar Bears – National Wildlife Federation. National Wildlife Federation, n.d. Web. 29 Mar. 2016. http://www.nwf.org/Wildlife/Threats-to-Wildlife/Global-Warming/Effects-on-Wildlife-and-Habitat/Polar-Bears.aspx
“Climate Change.” Climate Change. Polar Bears International, 2016. Web. 29 Mar. 2016.http://www.polarbearsinternational.org/about-polar-bears/climate-change