Impacts of Climate Change: Polar Bear in Danger of Extinction?
Average world temperatures are rising world-wide but the effects of global warming appear to be having a more profound effect on the Arctic than anywhere else. Arctic temperatures appear to be rising twice as fast compared to the rest of the world. Since 1979, the amount of summer ice has declined by about 30%. Because white sea ice has a cooling effect on climate by reflecting light away from the Earth's surface, its disappearance is speeding up the warming trend world-wide.
According to the Royal Society of London, England:
- It is a known fact that the burning of fossil fuels and certain land use changes lead to green house gases and increased global average temperature;
- It is very likely that the increase in green house gases over the past 50 years is a major impact on global warming;
- Climate change including temperature variations, precipitation and extreme weather events will have a varying impact around the globe;
- Ocean acidification is also an impact of increased atmospheric CO2 levels and will have negative consequences for marine ecosystems and the human populations that depend on them.
What is the Green House Effect?
- CO2 is necessary for life. It is necessary for photosynthesis in plants. As a green house gas, it keeps the earth warm enough to support life.
- The last 200 years have seen human activities, mainly involving the combustion of fossil fuels, result in the release of more CO2 and other heat trapping gases than in the prior 800,000 years of the earth's history.
- CO2 along with methane and nitrous oxides act as green house gases in the earth's atmosphere.
- The sun's rays hit the earth which absorbs vast amounts of heat some of which is re-emitted as long wave infra-red radiation. This 'heat' is absorbed by the green house gases and trapped on earth and like a green house, the temperature slowly rises.
Polar Bear Facts
- Species name: Ursus maritimus
- Range: mainly Canada but also found in Alaska, Greenland, Norway and Russia
- Status: In Canada, they are classified as an animal of Special Concern (1991)
- In the United States, they are classified as Threatened (May 2008)
- In 2006, the International Union for Conservation of Nature (IUCN) added the polar bear to its 'Red List' of the World's most imperiled wildlife
Global Warming and Polar Bears
Many scientists agree that global warming is the single biggest threat facing polar bears.
- The melting ice caps result in fewer ice floes on which these bears hunt their main prey which are seals.
- Fewer ice floes also mean a reduction in the shelter and transportation means for seals, walrus and the Arctic Fox.
- Because algae grows on the bottom of these floes, their reduction impacts further down the food chain as these algae support populations of cod, char, beluga and narwhal. Impacts like this on the marine ecosystem have negative repercussions for all members including polar bears.
- The denning areas of the polar bears of the Western Hudson Bay (an area of permafrost decline) are vulnerable to summer forest fires, in addition to being prone to collapse because of warm spring weather.
Did you know?
- Polar bears are the world's largest land predators.
- Polar bears survive the frigid Arctic climate due to two layers of fur and a thick layer of fat in addition to compact ears and a small tail which prevent heat loss.
- Polar bears have one of the slowest reproductive rates of any mammal.
- Polar bears typically give birth to twins in November or December in snow caves (maternity dens).
- There are no subspecies of polar bears but 19 distinct populations exist.
Evidence Supporting and Disputing Polar Bear Decline due to Climate Change
Recent evidence shows support for polar bear decline:
- Shorter hunting seasons seem to correlate directly with a 22% drop in the Wester Hudson Bay population of Polar Bears.
- A study of the Southern Beaufort Sea Population indicates a drop in cub survival rates and a decrease in the weight and skull size of adult males when compared to data from 20 years ago.
Some evidence also provides conflicting results:
- Very recent research published in early April of 2012 states that polar bears split from their nearest relatives, the brown bears, around 600,000 years ago.1
- Thus, polar bears were able to survive previous warm periods between ice ages.
- The ICUN Polar Bear Specialist Group (PBSG) concluded that while of 12 sub-populations of polar bears for which there is data 8 were declining. They also determined that 3 of these populations were stable and 1 polar bear population was in fact increasing in size.
1 Hirschler, Ben. News Daily. Polar Bears are no new kids on the block. Posted April 19 2012. April 22, 2012.
Although it is safe to say that global warming is having a negative impact on the global population of polar bears, it is likely not to be the primary cause for their extinction if the dire prediction comes to pass that polar bears will disappear from the earth in our lifetime. It seems that in their 600,000 years to date on earth they have survived more than one period of natural global warming. It is likely to be a combination of factors, albeit human-caused ones, that lead to their demise:
- habitat reduction;
- oil spills;
- over hunting of their food resources by humans;
- air pollution.