Polar bears are the mystic creatures residing in the northern apex of the world, they are one of the few animal that currently live with the least human encroachment. There are estimated about 25,000-31,000 number of Polar Bears alive today divided into 19 subpopulations (Rode, K. D., Robbins, C. T., Nelson, L., & Amstrup, S. C. 2015). The Arctic circle is one of the most delicate ecosystems on the planet, and because of fragile nature of the ecosystem (McConnell., et al. 2007), Polar Bears are the first ones to feel the detrimental effects of climate change. This paper will examine literature about factors affecting the natural habitat of the Polar Bears. Literature Review Ursus maritimus (Polar Bear) roughly translates to marine bear because they live on partly on ice and partly on land, specifically they utilize sea ice, sea ice is essentially ocean water that freezes and melts during the year forming sheets of ice-land that’s extends into the ocean (Andrew., et al. 2004).
After the boom of the industrial revolution, many machines that use fossil fuel began to be mass produced. Combustion of fossil fuel emits carbon dioxide that was once contained in the fossil fuel in the form of carbon. Released carbon dioxide in the atmosphere traps the solar heat and radiation in the atmosphere (Siegenthaler, U., & Oeschger, H. 1978). Increased carbon dioxide in the atmosphere is prevents the ice from staying frozen as it used to before the industrial revolution, Carbon fossil fuel combustion alters chemical and physical properties of the atmosphere and snow albedo, “from 1906 to 1910, estimated surface climate forcing in early summer from [Carbon] in Arctic snow was about 3 watts per square meter, which is eight times the typical preindustrial forcing value” (Ménégoz., et al. 2013) which BIOL 2140.001 2 translates to delayed formation of the sea ice and it melting away in the earlier months of summer. When ice melts away fast, it reduces the time Polar Bears have, to hunt for food. Polar bears hunt during summer months and hibernated during the winter months.
Monthly (black) and annual (red) BC concentrations from 1788 through 2002 measured in the Greenland D4 ice core. (B) Winter and summer BC concentrations show that long-term changes in BC were greater in winter (red) than in summer (black) during the late 19th and early 20th centuries. The free carbon radical in the air creates a greenhouse effect by capturing the heat and radiation from the sun with the atmosphere acting as a blanket, this contains the heat that would otherwise reflect back into space. The greenhouse effect is slowly increasing the temperature of BIOL 2140.001 3 the water in the oceans resulting in the temperature around the arctic circle to steadily climb. Because of the rise of atmospheric CO2, toward the end of the 21st century, seawater surface temperatures have been predicted to increase by 0.71–2.73 ?C in the surface ocean (Legrand., et al. 2017). “During the peak period 1930-40, the annually averaged temperature anomaly for the area 60° – 90° N amounted to some 1.7 °C”, the increased temperature of the ocean water is making it harder for ice to form and warmer waters are also changing the patterns of ice formation in the arctic circle (Bengtsson., et al. 2004). The places where Polar Bears usually hunt for seals and fishes are becoming less and less stable with the increased water temperature compromising the integrity of ice below the surface of the water.
Sea Ice that is not structurally sound is dangerous to the bear population that is not apt for swimming with the preys i.e. Bear cubs. Fig 1: Monthly March ice extent for 1979 to 2016 shows a decline of 2.7 percent per decade. BIOL 2140.001 4 Changing ice patterns is a sign of deteriorating polar caps, for a species that is depended on ice for its survival, melting ice is very harmful. The change in the temperature causes ice to freeze improperly, which gives way to structurally unsound ice. When ice isn’t frozen properly it breaks apart easily under pressure or any exertion (Xu, Z., Kim, D., & Kim, S. H. 2013). when the water waves hit the sea ice with force, it breaker apart because of the ice that didn’t compact during freezing, this can have detrimental effect on the main land since this increase the surface area of ice that is available for sunlight to melt, this is going to slower the formation of ice in the winter.
This can be dangerous to bears when they try to catch prey, as the ice can break away from the main sea ice. When sea ice breaks away from the main ice, it starts to float on the ocean as an ice berg. Polar bears eat seals (Hamilton., et al. 2017), and floating ice bergs mean that there is lots of places that seals can climb on and sit safely, away from the main sea ice. This makes it harder for the bears to get their food since the floating ice can provide a safe haven for the seals, they have to move farther away from their home to find food. A longer time to find food translates into more energy expend on trying to find food. To conserve energy they are being forced to move closer and closer to the edge of the sea ice. The ease of access to food was what helped to keep the bears in the heart of the arctic, but now with the loss of the accessibility, they are having to move and explore their options. Often times they are not successful in finding food. The life cycle of polar bears is eating and storing up energy during the summer and hibernating during the winter months.
The seals are harder and harder to capture due to the sea ice breaking away but some bears are fasting (Pilfold, et. al 2016) by not trying to catch the seals to conserve what little energy is left in them. There was a substantial change in the masses of observed bears. The bears that fast have learned hold a BIOL 2140.001 5 depressed metabolic state while on land to conserve energy due to the lack of food availability. “From the formation of annual sea ice in the autumn until breakup in summer, polar bears hunt seals from the ice surface. Hyperphagia occurs in spring, timed to the reproductive activities of ringed seals, and provides the energetic stores for survival through the open-water period, when prey are less available. Fluctuations in foraging activity are likely greatest in seasonal ice areas, where sea ice melts completely each summer and polar bears lose access to prey.” (Pilfold et al. 2012, 2015). Fig 3: Map of polygons, ice survey points (asterisks), and ringedseal sightings (diamonds) used to quantify shore ringed seal density, polar bear density on land, and the distance to sea-ice on the Alaskan coast of the Southern Beaufort Sea.
The scarcity of the staple food has forced polar bears to some extremes, they have been forced to move away from their main habitat and have tried to find food elsewhere. The human population of Southern Beaufort Sea have started to witness more bear sighting than before. the bears are raiding campsites and research areas to find sustenance (Schliebe., et al 2008). Wild animals only leave their natural habitat once their ecosystem has been altered and the polar bears are being forced just like any other animal, to move into the human territory because there is a lack of food due to the changing climate of the arctic. The sighting has increased over the past 10 years and it is expected to increase even more during the open water season, it has clustered around the expected ringed seal locations but it has raised security concerns for the bears food resources. It is possible that the bear population not living near human encampment might not have the privilege to get food and start dwindling in population. The polar bears living near the nest of arctic birds have found a more creative way to cope with the lack of food. they have started to attack the nests on these bird to provide temporary nourishment.
The Polar bear predation of Arctic bird eggs is increasing because of earlier sea ice breakup, which forces polar bears into nearshore terrestrial environments where Arctic birds are nesting but it is unclear whether nest foraging can provide an energetic benefit to polar bear populations, especially given the capacity of bird populations to redistribute in response to increasing predation pressure” (Dey, C. J., Richardson, E., McGeachy, D., Iverson, S. A., Gilchrist, H. G., & Semeniuk, C. D. 2017). The food sources that are available in place of the seals are not dense enough for the bears to last through their hibernation, the eggs and the scrape of food does little to keep the mass of adipose on the bear (Rode, K. D., Robbins, C. T., Nelson, L., & Amstrup, S. C. 2015). It was observed that the female masses were still trying to get to the location with energy dense BIOL 2140.001 7 food to provide for the cubs and herself. This was inefficient in energy since the cost of getting the getting energy efficient food was offset by the travel time and the energy cost of travelling the distance. The population of polar bears has started to decline over the past two decades, in an arial survey (Peacock, E., Derocher, A., Thiemann, G., & Stirling, I. 2011), the clusters of bears seem to be very sparse and scattered, the factors in the destruction of sea ice has caused the food factor to be sparse which in turn has affected the population density of the bears to decline.
Synthesis and conclusion The slight changes in the abiotic factors of the environment of the planet creates massive changes in the habitat of polar bears. the carbon in the air has caused ice to melt faster and the carbon dioxide in the water has reduced the speed the ice forms in the winter. The change in temperature has changed in the patters of ice formation and sea ice has been weaken due to the rise in temperature. Sea ice that is not compact and strong breaks away creating a safe haven for ringed seal, which are a staple diet for the polar bears. ice that’s breaking away also has become dangerous of the bears. Just like any other wild animal, the polar bear has had to improvise its diet to survive, they have started to raid the human settlements and have started to eat from the nests of the arctic birds. This has not been an improvement in their diet as the body masses have shown to decrease. The scarcity of food has pushed the polar bear population to decline. With the restoration of the sea ice and the patterns of ice and ringed seals returning to normal, there can be a chance for the polar bear population to bounce back in number.
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