Term Paper on "Endangered Species Biodiversity: Polar Bear"

Term Paper 8 pages (2596 words) Sources: 5

[EXCERPT] . . . .

Endangered Species

BIODIVERSITY CASE STUDY: POLAR BEAR

Distribution of the species

Polar bear (Ursus maritimus) is a maritime bear which is found largely within the Arctic Circle and its surrounding sea and land masses. Polar bears have circumpolar distribution. They are most commonly found in ice-covered waters of the Arctic Ocean, mostly within the Arctic region that surrounds the North Pole. Their most preferred terrain is the pack of ice surrounding the Arctic Ocean. The edges and the ridges of the ice provide the ideal hunting location for the polar bears. They have also been reported to travel as far as South of Greenland and Iceland but their range is limited by the sea ice at the Southern region. During summers, polar bears remain on islands with shrinking ice or on coastal regions with land fast ice but sometimes they also get trapped on land area where they are forced to endure the warm summers. During winters, polar bears can be found along both the northern and southern edges of ice that are formed along the coastlines.

Identify the modern biogeography region(s) in which it exists

The modern biographic region of the polar bear includes some parts of Canada, Denmark and Norway. The species is also found in Russia (Siberia, Northern territory) and in United States (Alaska). Some polar bears who become isolated also reach Iceland.

Summary of the evolutionary history

Scientific research indicates that polar bears first appear around 600,000 years ago. They are considered a subspecies of Ursus arctos, most commonly known as brown bear. Brown bears are the precursor to the polar bears who eventually developed characteristics for surviving the harshness of the Arctic region. Hence, they are believed to be evolved from brown bears when they underwent series of evolutionary changes in order to adapt themselves to the harsh environment of the Arctic regions (Miller and Schuster, 2012) Nature when exercised the extreme pressures on the brown bear resulted in better adapted subspecies i.e. polar bear.

Around 600,000 years ago, the Arctic Ocean was completely frozen and glaciers covered most of the surrounding areas. During this time, brown bears began to roam in search of food. It is assumed that a population of some brown bears got separated in the North from their ancestors because of competition for food. This population of brown bears was confined by huge glaciers and while most of the population perished in the harsh climate, some bears with evolutionary advantage survived the harsh environment and started bred. Over many years, these bears underwent the evolutionary changes developing the specialized traits for surviving the severe polar environment. Emerging as the survivor of one of the harshest areas containing ice, tundra and snow, their adaptations also resulted in white fur, sharp teeth and strong senses. When the life at Arctic demanded teeth for hunting the seals instead of eating berries, the teeth of polar bears evolved from that of brown bears. Moreover, polar bears grew the white fur that was necessary to hide themselves in the snow covered mountains and to give them hunting advantage.

Hence, these things acted as a major step towards evolution of new subspecies of brown bears, Ursus maritimus who evolved over a long period of time from terrestrial bears capable of surviving cold and hunting seals for food. Unfortunately, as the Arctic region is getting warm, polar bear's specializations that once helped them adapt to the harsh conditions and gave them an evolutionary edge are becoming the reason for this species downfall.

Identify the problem or concern for the species

Arctic region is an area that represents the rapid climatic changes that our planet is going through. The ecosystem that exists in that region is very fragile so even the slightest transformation will greatly influence the environment. One of the animals that have been highly affected by such changes is the polar bear. Polar bears are specialized to live in Arctic only so any change in the environment will make their survival difficult and they might be lost forever.

Some of the problems that are faced by polar bears and that are making their survival difficult in the Arctic are as following:

Climatic Changes:

One of the greatest challenges faced by the polar bears is the large-scale ecological changes that result from global warming caused by greenhouse gas emissions. Sea ice is the most important feature of the Arctic hence; Arctic region is extremely vulnerable to the recent climatic changes. Global warming is a threat to polar bears as it has reduced the thickness and extent of sea ice. These increasing changes will have a negative effect on the polar bear as the change in sea ice affects the access to the prey. Polar bears and their prey which includes mostly seals depend on the sea ice for their reproduction and relaxing. (Tynan and DeMaster, 1997) the Arctic's ecosystem is driven by the climate and polar bears act as an important indicator of the effect of climatic changes on the Arctic. Today, polar bears are facing threats as the ice thickness has been decreased during the past years.

If the extent of ice coverage will decrease in the polar region then this results in the availability of less food for the polar bears which will eventually lead to decrease in their reproduction rate. Due to the reduction of ice sheets, polar bears are forced to move to shore for longer periods of time where they rely on stored body fats that they reserve during spring season for survival. In such situation where they move on to land they become easily vulnerable to hunting by the humans. If these periods become elongated then polar bears start dying. Warm temperatures reduce the thickness of ice sheets and increase ice drifts hence, polar bears have to walk against increased movement of ice that increase the usage of their stored energy and reduce their reproduction.

Pollutants:

Toxic pollutants from industrial activities are driven towards the Arctic through air, river and oceans. (Arctic Monitoring and Assessment Programme, 1997) There are certain areas in Arctic like Kara Sea and Barents Sea that are intoxicated with high levels of pollutants. Pollutants tend to endure in the environment and pose a threat to polar bears. Many pollutants such as organochlorines get accumulated in the food chain of the polar bears. These pollutants result in a variety of negative way, s such as damaging the neurological, growth and reproductive system and decreasing the capacity of their immune system to fight germs and diseases. Organochlorines have capacity to bond tightly with the fat molecules. Since polar bears eat a diet rich in fat like the blubber layer of seals, they are more vulnerable to these pollutants. The accumulation of these pollutants is also harmful for the reproduction system of the polar bears. The female polar bears are food deprived during impregnation hence; during this time they use their stored fat for energy where these pollutants are also stored. The cubs are also nursed on the fat rich milk so they are also directly exposed to the pollutants from their mother.

Oil Development and Hunting:

Oil Development in the Arctic region presents a grave threat to the polar bears ranging from oil spills to human-bear encounters. The polar bears and their prey get directly exposed to the oil when oil spills in the sea results in oil being concentrated between ice caps. If any oil spill occurs in the marine habitat then oil will damage the fur of the polar bear and will decrease its insulating effect. The reduction in the insulating effect means that a bear must consume a lot of energy by increasing the calories in take to stay warm. (Norris, Rosentrater and Martin, 2002) Polar bears can also ingest oil by eating the contaminated preys like seals and seabirds. This ingestion of oil can cause toxicity and damage the liver and kidneys of polar bears. Moreover, recent oil development and exploration have also caused disturbance at the den sites where pregnant female bear settles for giving birth to the cubs. Hence, if the disturbance occurs close to the den site then female bear abandons her offspring or leave the den prematurely.

Other threats to the polar bears also include hunting. (Aars, Derocher and Lunn, 2006) They have been hunted for thousands of years now for food, clothing and other religious purposes. Sometimes, commercial hunting is also carried out for their hides. The extensive hunting of the polar bears can push them at the verge of extinction. Hence, if the hunting activities won't be regulated properly then it can have considerable impact on the polar bears due to their slow rates of population growth.

Attributes/traits of the species that make it vulnerable

Polar bears are especially specialized mammals which depend on sea ice for hunting its food and for other important aspects of its lifetime. It is often known as a maritime bear because it spends many months at sea. Its preferred terrain is the sea ice… READ MORE

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