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The recent increase of man-made carbon emission and pollution worldwide has created many environmental problems, with the most prominent one being global warming. Global warming occurs when the carbon dioxide and other air pollutants trap the sun’s radiation bouncing off Earth surface, causing the Earth to get warmer and warmer. “The combination of warmer temperatures and vegetation growth means there is more overlap between the species and I’d expect that overlap to increase,” Chris Servheen, a grizzly bear expert at the University of Montana, told the Guardian in 2016. Several ecosystems are affected by global warming, including the freshwater ecosystems, terrestrial ecosystems and the ocean ecosystems. In this essay, we will take an in-depth look of how global warming has impacted the ocean ecosystem near the polar arctic circle, more specifically the ecology of the species Ursus maritimus, also known as polar bears. Increase global temperature has not only caused the ice sheets to melt which makes it harder for polar bears to hunt or find shelter but also result in rising sea levels destroying several coastline ecosystems.
In recent years global surface temperature has increased by an average of 0.2°C per decade in the past 30 years, it has produced shifts in the distributions and abundances of many species causing some of them to be endangered or near extinction. The average increase is similar to the warming rate predicted in a global climate model simulation conducted in the 1980s with transient greenhouse gas change (Hansen et al, 2006). Hansen and his team measured and compared sea surface temperatures in Western Pacific with paleoclimate data in the past, they suggested that this critical ocean region, and Earth as a whole, is within 1°C of the maximum temperature in the past million years, almost as warm as the maximum temperature during the Holocene period (Hansen et al, 2006).
A report conducted in 1972 on global warming stated, “burning a large part of fossil fuel can result in a rising temperature little above that experienced in the climatic optimum in ice age, it must not be overlooked that variations in climate of only a fraction of a degree can have considerable natural fluctuation…a decrease of incoming solar radiation of only about 2% might lead to complete glaciation of the earth. The effect of the decrease of ice cover which would accompany an increase of world temperature is, however, less significant” (Sawyer, 1972), demonstrating that there is a strong sense of acknowledgement of the effects that can be caused by increased gas emission.
The conclusion of this 1972 report is that more studies will need to be done in the future for better assessment of where the carbon dioxide goes after it has been dispersed from chimneys, and in particular the long term balance with the ocean is needed in the future. This report demonstrated that there is awareness of the effects of carbon dioxide increase. However, they were more concern about decreased solar radiation causing glaciation to the Earth, as suppose to the increase of global warming that is occurring in the present time (Sawyer, 1972).
As Steven Amstrup pointed out in his report, “the levels that global greenhouse gas emissions reach in the upcoming decades will have a tremendous influence on the abundance and distribution of polar bears in the future” (Amstrup et al. 2010a). Polar bears will likely be wiped out from a majority of their present day habitat if carbon emissions continue to rise at the rate it is currently in throughout the 21st century (Amstrup et al. 2010a).
As a result of recent global warming, the ice sheet in the Arctic is shrinking at a rate of approximately10% per decade, and Arctic summer temperatures scorching to around 2 °C higher than 50 years ago. About 1.3 million square kilometres of ice sheets have been lost over the past four years, that is an area equivalent to three times the size of California (Simonite, 2005). A recent study by US Geological Survey concluded that polar bears are likely to lose 42% of their summer sea ice habitat by mid-century at this rate (Courtland, 2008) of nearly 9% ice loss per decade. By September of 2060 the Arctic Ocean will likely be ice free (Comiso, 2006). However, as some scientists suspect, the date will come sooner by 20 years to 2040 if the shrinking were to accelerate. The ice sheets are not only just shrinking in its surface area, but also in its depth, as recorded by submarines and radar images from satellites. The declining crisis seems to continue even in the winter (Comiso, 2006).
The surface area of Arctic sea ice has reached an all time low, reducing from 7 million square kilometres, which has been a long term average since 1979, to less than 6 million square kilometres in 2002. Since then, it has continued to drop or stay at near-record low levels. By September of 2007, the surface area of the Arctic was covered by what was thought as a record low 4.8 million square kilometres of ice until recently. It was announced on September 2012 that the ice extend have now dropped to around 3.52 million square kilometres, shown in figure 2 (Schiermeier, 2012). By 2100, the ice sheets in Antarctica alone has the potential to contribute more than a metre of sea-level rise and more than 15 metres by 2500, if emissions continue to be uncontrolled (Deconto and Pollard, 2016).
In 2017, a group of researchers analyzed a 35-year satellite record to examine each of the 19 population areas where polar bears were spotted. The areas range from 53,000 to 281,000 square kilometres in size. From those records, the researchers found a trend showing sea-ice retreating earlier in spring and advancing later in autumn. The time span between the sizes of the sea ice when it reaches the maximum surface area in March to the minimum size of sea ice in September has lengthened by up to nine weeks since 1979 (Sterna and Laidre, 2016). This is a very concerning discovery because it disrupts the life cycle of the plantations around it and also the hunting and hibernation season of the polar bears.
When sea ice retreats earlier than average in spring, this allows the ocean more time to absorb heat from the sun. This, in turn, delays the freeze-up period in fall because the extra heat stored in the upper surface of the ocean throughout summer must be released to the atmosphere first before sea ice can slowly begin to form. On the other hand, a late spring sea-ice retreat restricts the ocean from absorbing as much heat, which leads to sea ice forming earlier in the fall (Perovich et al., 2007). It’s a negative correlation because the change of temperature and humidity can influence factors such as long-term climate patterns and patterns short-term weather events.
Due to the massive loss of ice sheets, an unusual large amount of polar bears have been spotted swimming in open sea as far as 95 kilometres offshore. In previous Septembers before 2005 only 4% of polar bears sighted were swimming, but during the September of 2005, 20% of polar bears seen in the area were in the water (Simonite, 2005). The excess amount of swimming to find an ice sheet to rest on has resulted in many polar bears drowning from exhaustion or hunger (Simonite, 2005). To make matters worse, polar bears metabolism seems to remain the same even when food is sacred, making it even harder to survive and adjust to the climate change. Overall, changes in sea ice have been shown to significantly impact on polar bear productivity, body condition, distribution and abundance (Bromaghin et al., 2015).
As previously mentioned, the US Geological Survey study stated that polar bears are likely to lose 42% of their summer sea ice habitat by mid-century. As a result, the polar bear population would be at risk of being cut down by an estimated 25,000 or two thirds of the current population (Courtland, 2008). As of today, there has been a 40% population loss between 2001-2010 from 1500 to 900 bears in northeast Alaska and Northwest Territories alone (Bromaghin et al., 2015). From 2004 to 2006 alone, the low survival rate is responsible for 25-50% decline in abundance. Behaviours such as cannibalism and attempting suicidal swims in polar bears have been reported by several sightings as a result from melting sea ice, leaving the polar bears with longer distance to travel or scavenge for food (Amstrup et al. 2006b). On the west side of Hudson Bay, researches have shown that young bears are less likely to survive after earlier sea-ice break-ups, a process which now occurs roughly three weeks earlier than it did 30 years ago (Obbard, M. E. et al., 2006) due to ice retreating earlier in spring and advancing later in autumn, as noted by researchers Harry L. Stern and Kristin L. Laidre (Stern and Laidre, 2016). On June 2005, the world conservation union (IUCN) polar bear specialist group announced to have the conservation status of polar bears altered from “least concern” to “vulnerable”, as they expect a 30% population decline within the next 35 to 50 years, due to loss of their ice habitat (Simonite, 2005).
The crisis of reduced land mass availability from sea ice is expected to increase furthermore as temperature continues to rise unless conservation strategy is being implemented. On May 15, 2008, the United States Fish & Wildlife Service listed the polar bear as an Endangered Species (Runge, M.C. and Kohout, J, 2015). As stated “reducing greenhouse gases is one of the most important ways to prevent more sea ice habitat loss for polar bears that rely on it.” Therefore, the U.S. fish and wild life service have created a conservation management plan to conserve and recover the population of polar bears. The plan includes, “managing human- polar bear interactions to ensure human safety and conserve polar bears” since they would be spending more time on shore due to limited ice sheets. (Runge, M.C. and Kohout, J, 2015). Within the plan it was also mentioned that after the Gulf of Mexico spill in April 2010, US government has clamped down on offshore oil drilling and also stopped oil company like Shell to drill in the Hanna Shoal, Alaska, due to the risk of future oil spills that can occur and potentially ruin the remaining limited habitat for polar bears and other local marine animals (Runge, M.C. and Kohout, J, 2015).
A big announcement was also made on December 20, 2016, when President Obama announced permanent protection for 115 million acres of federal waters in the Beaufort and Chukchi Seas, where a majority of polar bears can be sighted. The government of Canada also took action for the Arctic by approving moratoriums on commercial fishing in the Beaufort Sea and new offshore fossil fuel production (World Wildlife Fund, 2016).
As the researchers in the Cryosphere report stated, “Their (polar bears) dependence on sea ice means that climate warming poses the single most important threat to (polar bears’) persistence” (Sterna and Laidre, 2016). Steven Amstrup of the US Geological Survey and his colleagues examined a models of future sea ice circulation and found NO signs of warming beyond which can cause the ice to disappear permanently and irreversibly. Therefore, by controlling the greenhouse-gas emissions it “should help preserve the polar-bear habitat and Arctic ecosystems” as a whole (Amstrup et al., 2010). Several organizations like World Wildlife Fund and Polar Bear International are all actively trying to raise awareness and stop the polar bear crisis. It is now up to us to educate others as well to reduce carbon emissions and prevent further global warming for the better of this world.
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