Extinction Of Polar Bears Essay

Global warming has become a more prominent issue every decade since the mid 1900s. The increased temperatures are leading to substantial ice loss. This loss in ice is causing severe destruction to polar bear habitats and homes and is leading to their extinction. It also is affecting their food supply. Global warming is making it harder for polar bears to repopulate and is causing a decrease in the overall size of each bear. The chemicals associated with global warming are getting into the food chain and eventually into the polar bears themselves. Global warming is causing the extinction of polar bears in the arctic because it’s destroying their homes, decreasing their food supply, is affecting chemicals in the air and in their food, decreasing the average size of the bears, and contributes to a decrease in reproduction.
Scientists all across the world have spent many decades trying to figure out the cause of global warming. They have determined that global warming is the result of greenhouse gases such as carbon dioxide,

water vapor, methane, and nitrous oxide being trapped in the atmosphere. Sunlight enters the earth’s atmosphere and is then radiated back towards space. However, the greenhouse gases absorb almost 90 percent of the heat and then re-emit it back into the atmosphere (Climate Change Causes). This causes an increase in the earth’s overall temperature because the heat is trapped. Human activities are the leading cause of the change in greenhouse gas levels, the most prominent being the burning of fossil fuels. Carbon from the fossil fuels combines with oxygen in the air to form carbon dioxide (Climate Change Causes). Humans also continue to wipe out forests for agriculture and commercial use. With a continuously decreasing number of trees, there are fewer plants to remove the carbon dioxide from the air, which can stay in the atmosphere for multiple centuries. “The average global temperature has increased more than 3.6 degrees Fahrenheit since the pre-industrial era” (The Causes of Global Warming). “Nine of the warmest years on record have occurred within the last ten years” (The Causes of Global Warming). Global warming is becoming a more and more important issue every year as it affects not only nature and animals across the globe, but humans ourselves.
There are currently 20,000 to 25,000 polar bears that are apart of 19 different species that can be found almost anywhere in the Arctic region. Over 40 percent of the bears, however, live in northern Canada (Endangered Polar Bear). Male polar bears weigh roughly 700 to 1,600 pounds and range from 7.5 to 10 feet long. Females are about half the size of males, as they weigh 300 to 500 pounds and are 5.5 to 8 feet long (Polar Bears). Unique to polar bears is a 4.5-inch layer of fat under their fur. The fat is crucial to the bears’ survival as it protects from heat loss while they are in the water. On land, their dense fur coat is the main source of heat. The fur coat is so thick that it prevents almost all heat loss and the polar bears can quickly overheat when running on land (About Polar Bears). Polar bears’ heavy fur coats along with the increased temperatures caused by global warming can be very dangerous for the bears as it can lead to severe overheating.

Polar bears are considered marine animals because they spend the majority of their time on the water sitting on sea ice. The ice provides a place for them to hunt, breed, and sometimes create maternal dens, where the mother will raise her cubs (Polar Bear Habitat). Polar bears use the sea ice as a hunting ground for their main source of food, ringed seals. They most commonly hunt the ringed seals through a form of hunting known as “still hunting.” The bear uses its excellent sense of smell to locate a seal-breathing hole in the ice and then crouches down, silently waiting for a seal to appear in the water below (Polar Bear). The sea ice provides a perfect place for the bears to hunt and catch their prey because it traps the seals in a small area, making them easily accessible to the bear. During the summer when there is less sea ice available, polar bears come ashore and feed on plants, such as seaweed, and berries, most commonly bearberries (Endangered Polar Bears). Polar bears also use the ice as a breeding ground, where they find a mate and start a family. Finally, the mother bears create maternal dens on the ice as a place where they give birth to their cubs and keep them sheltered during their early development. *Closing sentence*
The biggest threat to polar bears is habitat destruction resulting from global warming. Among the threats from habitat destruction, sea ice decline is the main factor directly affecting the survival of polar bears. Sea ice decline begins because increased levels of greenhouse gases trap heat in the atmosphere. This leads to a rise in overall temperatures on earth, including ocean temperatures, which causes sea ice to melt more rapidly. In fact, sea ice is declining at a rate of 13 percent per decade (Palmer). Add a fact that tells why the 13% rate of decline is bad… what was the rate of decline decades ago? With less sea ice available, many polar bears are forced to travel hundreds of miles to find viable hunting grounds. This is not an efficient means of gathering nutrition. The bears that do not follow the ice are forced to stay ashore and rely primarily on a diet of plants, which does not result in the healthiest outcome for the bears, as they are evolutionarily designed to subsist mainly on meat based proteins (Endangered Polar Bears). In addition, less sea ice reduces the size of the breeding ground, possibly making it harder to find a mate and start a family. The disappearing ice also leaves less space for mothers to build dens to house and protect their young. ***closing sentence
Polar bears main source of nutrition is seals. When hunting is good and a polar bear is in good condition, the bear will eat only the seal's blubber and skin. Scientists have found that when polar bears only eat seal fat, their cholesterol levels drop due to the omega-3 fatty acids found in the seals’ fat. Lower cholesterol levels improve the overall health of the bear and decrease the risk of premature death. In summer, when ice levels decline, polar bears either follow the ice to stay with their food source (Endangered Polar Bears) or stay ashore and change their diets dramatically. The decreasing ice levels are forcing the bears to spend more time on shore, which prohibits their ability to hunt seals. Rather than relying on seal blubber and skin for their nutrition, polar bears are restricted to on shore diets that primarily consist of berries and plants. This diet does not provide enough fat or calories to keep the bears healthy (About Polar Bears). Closing sentence
Another factor that is affecting polar bears is the chemicals and pollutants that are brought on by human activity.

The most frequently found substances are called Persistent Organic Pollutants, or POPs. Examples are industrial by-products, heat resistant chemicals such as PCBs, and pesticides like DDT (Threats to Polar Bears). “Bears with high levels of some POPs have low levels of vitamin A, thyroid hormones, and some antibodies (Threats to Polar Bears). These are important for the growth and reproduction of the bears. High levels of POPs are frequently found in mother polar bear’s milk. This causes the cubs to often have lower survival rates due to poisoning (Threats to Polar Bears). The pollutants start in the lower levels of the food chain and work their way up. They accumulate and the concentration gets higher for every step up. The POPs are hard to get rid of meaning they stay in the food chain for many years (Threats to Polar

Bears).
Oil exploration is another common factor that affects polar bears and their habitats. As southern reserves dry up, humans are forced to move closer to or even into the arctic regions to drill for oil. Oil spills have proven to be detrimental to polar bears. Contact with an oil spill can reduce the insulation of the polar bear’s fur.