This paper was written as part of the 2010 Alaska Oceans Sciences Bowl high school competition. The conclusions in this report are solely those of the student authors.
The Effects of Global Warming and Thinning Sea Ice on Polar Bears (Ursus maritimus) and Other Animals of the Arctic
The effect of global warming has been negative on polar bear populations and other populations of the Arctic region. This is shown by more cubs and young animals dying each year; dying of starvation and in some cases drowning from sheer exhaustion. Ringed seals are more affected by the earlier melting of the sea ice, this causes the ice lairs built for the pups to melt before the pups are mature enough to defend themselves. This opens them up to greater predation from polar bears and other endemic predators to the area. As well as the ice melting earlier, it isn't growing as thick in areas where ringed seals are usually found. To adapt to this change the seals must move farther north, in the latitudes where more polar bears are found. These two species, while separate entities, are linked together by one limiting resource. This resource is the Arctic cod, upon which ringed seals are known to feed off almost primarily. Due to the increasing water temperature the eggs laid by female Arctic cod are unable to mature, causing an ever decreasing population.
To save this delicate food web and cycle of life, we must act quickly. Monitoring the commercial fishing of Arctic cod is only one small step that will help bring the Arctic food web back to equilibrium. To make a larger impact, we as humans must think of what kind of impact we are putting on the earth, and we must consider how we may be able to reverse the rate of declination in these populations. Some ways are to create refuges or sanctuaries for a particular population, to monitor the hunting or commercial fishing of these animals, and to put polar bears on the Endangered Species List.
Causes and Effects of Global Warming
Global warming's impact on the sea ice has drastically altered the habitat for polar bears, ringed seals, and Arctic cod. These alterations include the thinning and melting of the Arctic sea ice prematurely, causing changes in mating, resting, and migratory habits that had long been established. These trends must change, or we will face the extinction of many key Arctic species.
By the 1960's the atmosphere was being affected enough to be visible to the naked eye. One contributor to the emission of carbon dioxide is large shipping vessels. Not only do these ships contribute greatly to the amount of carbon dioxide in the atmosphere, but they also release several other harmful pollutants. Such as toxins from painting, dry cleaning, picture development, and plastics. Even though ships are prohibited from dumping floating trash within 25 miles from shore, they are however permitted to dump trash that has been ground into pieces no larger than one inch when at least 12 miles from shore (Oceana, 2009).
Excess of carbon dioxide in the atmosphere caused by green house gas acumulation has to go somewhere, and that place is the ocean. Currently the oceans are acting as a carbon dioxide buffer, absorbing the carbon dioxide and consequently raising the pH of the ocean. This ocean acidification erodes the calcium in corals and other shelled marine organisms. A report on "The Impacts of Ocean Acidification on Coral Reefs and Other Marine Calcifiers" documents that worldwide, the oceans have absorbed almost 118 billion metric tons of carbon from the 1800's to 1994. The increase of acidity lowers the amount of carbonate ion, the building block of calcium carbonate that many marine organisms rely upon to grow their exoskeletons and create reef structure (National Center of Atmospheric Research, 2006). For the human population this absorption of carbon dioxide by the oceans has benefited by minimizing some impacts of global warming. However based on the Intergovernmental Panel on Climate Change (IPCC), carbon dioxide emission scenarios and ocean-atmosphere models show a resulting decrease in the surface water pH of about .3 pH units (NOAA/PMEL). It has been shown that the Southern Ocean, the most important "carbon absorber" of all the oceans has dramatically slowed its uptake of carbon dioxide because of climate change (Oceana, 2009).
The Intergovernmental Panel on Climate Change calculates the risk of climate change caused by human activity. The IPCC published a newer climate model showing that the global surface temperature will perhaps rise another 1.1 to 6.4°C in the 21st century (IPCC). Scientists believe this increase in the global average temperature is due to the increase in the concentration of greenhouse gases such as of course, carbon dioxide, methane, and fluorocarbons. These gases create a blanketing effect, so when sun rays pass through the earth's atmosphere and are absorbed by the earth, it causes the earth's surface to warm. Part of this absorbed sun energy is then reabsorbed back into the atmosphere as long wave radiation, but because of the greenhouse gas blanket, most of this long wave radiation can't escape, so they are reemitted downward causing the lower atmosphere to warm (Cohen, 1998).
The World Wildlife Fund recently published an article on global warming and its affect on Alaska. It states "Alaska has warmed more than twice the rate of the rest of the United States..." (WWF, 2009). This increased temperature has already been the cause of earlier snow melt, reduced sea ice, widespread glacial retreat, and permafrost warming. While the current climate model predicts an increased amount of precipitation in Alaska, it also predicts increased rate of evaporation due to the higher air temperatures which will cause much drier conditions. These conditions as predicted will be the cause of reduced soil moisture.
Scientists believe these temperature changes have caused the increased intensity, and occurrence of El Niño and La Niña because of warmer ocean temperatures caused by global warming. In 1998 scientists from the National Oceanic and Atmospheric Administration (NOAA) explained that the increase in evaporation from land and accumulation of moisture to the air has caused the storms and floods related to El Niño to become more frequent (West). Kevin Trenberth, a climatetologist from NOAA in Colorado believes that because ocean currents and weather systems may not be able to release the excess buildup of heat in the tropical seas, El Niño may be acting as a sort of pressure release valve. He noted that during El Niño storms, warm waters spread across the tropical Pacific, causing large amounts of water to evaporate, and release heat when the evaporated water condenses into clouds and rain. El Niño events transfer heat from ocean to atmosphere, which causes the global temperature to increase about 0.1°C (Kevin Trenberth, 2000).
NASA published a study on the warming of Arctic oceans by Dr. Josefino C. Comiso. This study contrasted the climate during the 1980's to the 1990's, and found that most of the Arctic has warmed considerately over the last decade. The result of this warming directly causes the declination of perennial sea ice formation. These warming tendencies may affect the ocean processes, which will impact Arctic and global climates because liquid water absorbs sun energy instead of reflecting it as ice does. As oceans warm and ice thins, more and more solar energy is absorbed which leads to further warming, and a continuation of this damaging cycle. The dynamics of this cycle may alter the temperatures and salinity of ocean layers, which will cause a dramatic change in circulation, and marine habitats (Steele, 2007). Comiso's study also showed that temperature changes vary by region and time of year. For instance while most of the warming occurs over the Arctic, it was found that Greenland is cooling. David Rind continued to say that if the temperature increase continues in high latitudes and the sea ice extent declines, the thawing of Arctic soils may release even more carbon dioxide and methane currently trapped in permafrost, and the warmer ocean could release natural gases from the ocean floor. This would, in the end, release even more greenhouse gases into the atmosphere further exacerbating the current trend of global warming.
The rise of the sea level increases the vulnerability of coastal communities to flooding and will cause land to be lost to erosion. Warming will increase the amount of water exchanged between the oceans atmosphere and the land. The increase in evaporative rates will possibly result in drier soils. The elevated evaporative rate will cause the water cycle to increase in intensity, the result of which will be frequent droughts, and floods. This prediction has already occurred as in the early 90's two floods that occur every 100 years occurred in less than five years in the midwestern United States (Encyclopedia Britannica, 2009). The effects of global warming on humans are likely to be negative. A decrease in day and night temperatures will cause more thermal extremes, which may cause an increase of deaths due to heat stress. Others result in the warming the earth's surface will cause fewer "killing frosts"; these frosts kill pests such as mosquitoes which will cause an increase in vector-borne diseases. These diseases include malaria, yellow fever, and encephalitis (Holdren, 2006).
Polar bears and ringed seals both depend on sea ice for hunting, mating, and resting. Yet due to the earlier melting, and later formation of sea ice the polar bears are dying of starvation, and in some instances, drowning (Melville, 2003).
Polar Bears (Ursus maritimus)
Each year, polar bear (Ursus maritimus) populations are declining rapidly at dangerous rates, especially the Chukchi Sea, southern Beaufort Sea, Norwegian Bay, Kane Basin, Lancaster Sound, Baffin Bay, Davis Strait, and the western Hudson Bay subpopulations of polar bears. The western Hudson Bay polar bear population declined 22% in 17 years, (Polar Bears and Conservation, 2009) and the decline was preceded by weight loss, a decline in cub survival rates, and smaller males, all of which we are seeing in the Chukchi Sea polar bear subpopulation that Alaska and Russia share (Global Warming Reduces Polar Bear Survival Rate, 2006). Of the nineteen subpopulations of polar bears, the McClintock subpopulation is increasing (WWF, 2009), three are stable, eight are decreasing, and seven have insufficient data (Polar Bears and Conservation, 2009). Eight out of nineteen polar bear subpopulations, when only around 20,000-25,000 polar bears are living worldwide, is alarming. According to the U.S. Geological Survey, two-thirds of all polar bears may become extinct in Alaska by 2050, and all polar bears may become extinct within this century (Polar Bear SOS). All of these problems are due to melting ice floes and a lack of being able to find food, making polar bears adapt by moving closer inland or die. Melting ice floes, the main reason for polar bear endangerment, is due to global warming.
Polar bears are miraculous creatures, being the largest land carnivore weighing up to 1,500 pounds. Although they have many roles in their Arctic environment such as stabilizing ringed seal populations, being at the apex of the Arctic food chain is their major function. Studying the apex predators of a certain area tremendously helps scientists understand how healthy that area's ecosystem is. With the help of polar bears, scientists are able to understand the need to protect the Arctic ecosystem and see what other major problems may be elsewhere in the Arctic (WWF, 2009).
One reason polar bear populations are declining is due to the ice floes melting. In the summer of 2005, it was recorded that the ice cap receded 200 miles further north, and in the September of 2005 the ice cap off of Alaska retreated 160 miles north (Iredale, 2005). Ice floes are decreasing due to global warming, which increases the temperature of the Arctic region greatly, and has caused the loss of sea ice to be as big as the sum of Alaska, Texas, and Washington combined (Polar Bears and Conservation, 2009). Global warming is caused by anything as harmless as leaving the light on in your room, to pollution caused by Arctic oil drilling.
Ice floes are extremely vital to the survival of the polar bear populations. They allow the polar bears to hunt seals and other marine mammals including the occasional walrus or whale. Ice floes are also the sites where polar bears find their mates, and the bears stay on the floes up to a week to breed. They are then home to polar bear dens, and are a place for polar bears to rear their cubs, teaching them how to hunt and other necessary skills. Without ice floes, polar bears will not be able to carry out all of these functions extremely necessary to maintain life and their population (Monga Bay, 2006).
Another reason we are not seeing an increase in the polar bear population is because less cubs are surviving. In the 1980's, about 65% of polar bear cubs were surviving. Now, the survival rate is less than 43%. An average litter size is now one cub, when it used to be two or three cubs per litter. The cubs are dying mainly from starvation, and lack of nourishment from the nursing mother. We are also seeing polar bears eating the cubs for food (Monga Bay, 2006).
Due to the ice floes melting, polar bears are drowning from exhaustion, starving to death from lack of food, or sometimes causing them to move inland. The polar bears do not have enough time on the melting ice floes to accumulate the necessary body fat reserves they need to maintain life during summer months, so they move inland because they cannot find food (American Society of Mammologists, 2008). They then start to interact with human settlements and eat indigestible garbage such as plastic, car batteries, and Styrofoam. When the polar bears do stay on the ice floes, however, we find that many have to swim long distances to hunt and end up drowning. Some even starve because they cannot find food, which leads them to resort to cannibalism (Iredale, 2005).
Polar bear survival is also important because their ecological niche is regulating ringed seal populations in that area. Without polar bears, ringed seal populations would flourish, which would cause a collapse of the Arctic food web because ringed seals eat other organisms, and those organisms' populations would possibly decrease, affecting other organisms that make up the Arctic food web (Amstrup, 2007).
Although polar bears have survived changes in their environment for thousands of years, there are so many more factors contributing to their possible extinction right now. They are now interacting with oil, plastics, and other pollutants that are highly toxic and dangerous if ingested. They are coming in contact with more boating vessels that disrupt their habitats and introduce them to oil and other toxic substances. The major climate change due to pollution of our planet is also taking a major toll on them by melting ice floes and making them move inland.
By monitoring polar bear populations and living territories, we will be able to see if the population is increasing, and if it is increasing, where. We will also be able to see if polar bears are moving inland, or starting to go back to original territories. By monitoring the population of ringed seals and their migratory patterns, we will be able to see how long the feeding period for polar bears is, see if there is an increase or decrease in ringed seal population, if it is affecting polar bears, and if the polar bears move further out when the ringed seals come. By regulating boating in the Arctic, we will be able to see if the boats contribute to the breaking of the ice floes, and if more polar bears die when boating is occurring in their habitats. By putting the polar bears on the endangered species list, we will be able to prevent polar bears from being hunted by the indigenous people of the Arctic regions, and more people will be reaching out to help the polar bears.
If we, as people, do our part to prevent global warming from escalading, polar bears may once again be able to thrive. We can do this by preventing so many commercial boating companies from polluting the Arctic, stop littering since it all eventually goes to the ocean, and be more eco-friendly by recycling, inventing automobiles that are better for the environment, and stop polluting the planet with green house gases that are contributing to global warming. Simple steps such as using walking or biking as a form of transportation a few days a week and not leaving lights, computers, or other electric appliances on can prevent some carbon emissions can make a difference. If we do not act now, we may lose these wonderful animals forever (Causesofglobalwarming.net, 2008).
The population of ringed seals is declining at an alarming rate do to the melting ice caps. If we don't do something soon, ringed seals will end up on the endangered list. The major problem is global warming is that the ice floes are melting due to the warming temperature. The ringed seals depend on the ice floes for protection and for access to their feeding grounds (Smol, 2009).
Ice packs have begun breaking up earlier than in the past due to global warming, this causes the ringed seals to become easier prey for the polar bears. The pups are very dependent on the ice lairs because it keeps them safe until they are old enough to be on their own. Without these lairs the pups are more vulnerable to exposure and predators, and they also develop a poorer body condition. If the pup's mother dies before the pup matures, the pup will die. Polar bears rely greatly on the ringed seal as a main food source, and if the seal pups continue dying off, the population of this species will continue to rapidly die off.
The ringed seals feed on Arctic Cod, which may eat contaminated organisms, causing the ringed seals to build up dangerous toxins in their bodies. Other predators, such as the polar bears, feed on the ringed seals, it is possible that these other predators would also get contaminated with these toxins. The contamination may get worse if nothing happens soon. If the contamination worsens, more and more ringed seals will die off; this extreme species death will cause this species to become extinct (National Geographic, 2009).
If the contamination level in Arctic cod decrease, there will be fewer ringed seals with high to moderate levels of toxins in their systems, hopefully making it possible for the ringed seals to increase their population (Defenders, 2009).
Since the ringed seals are moving further north because of the ice floes melting, they are moving closer to their predators such as the polar bear. They move north because they are trying to find thicker ice in the north, this migration moves farther away from their natural habitat and natural feeding grounds. Global warming is making it hard for the ringed seal to live a normal life. They depend on the ice floes for protection, to raise young, and to rest. If they can no longer depend on the ice, their young pups will end up dying off, causing the population to decrease even more. The ringed seal is the main food source for the polar bear, and if the ringed seal keeps moving further north, they will become easier prey to the polar bear, thus making the population decrease more. Another reason ringed seals move farther north is because if the snow dens for their pups melts, they need to move to where there will be thicker ice so that the pups can stay protected until it is old enough to be on its own in the wild (Smol, 2009).
Polar bears are dependent on ringed seals, which are dependent on the Arctic cod, which are decreasing in population. Arctic cod are dependent on the Arctic krill, copepods, and amphipods. Due to the warming waters, these small organisms have yet to adapt to the change and their populations have begun rapidly decreasing. The cod have been dying and are unable to reproduce quickly enough for the dramatic change, therefore the ringed seals haven't been able to reproduce quickly enough either because their own food supply is cut so short by this loss of population. This chain reaction continues to the polar bears, which are unable to find enough food since the ringed seals have been so greatly affected by the loss of Arctic Cod.
Arctic Cod have a major effect in the Arctic food web; even the smallest glitch can ruin everything. The Arctic cod are not only necessary for seals and polar bears; they are also the main food source for birds, whales, and even other fishes. The location of the Arctic cod also have an effect, they can be found everywhere from depths of 900 meters to right underneath the ice caps. The Arctic cod favor temperatures below 4°C and are one of the few fish that thrive in temperatures below 0°C. Antifreeze proteins in their blood are one evolutionary adaptation responsible for this ability. Furthermore, the Arctic cod have a short life span usually of up to six years. The average female Arctic cod has up to 21,000 eggs, but due to the warmer waters, the eggs have been dying and have not been able to mature. Since 1979 the fish population of the Arctic cod has decreased over the years. While global warming has been a major issue lately, and because the Arctic caps are slowly melting, the predators of the Arctic are relying on the Arctic cod to obtain food (Murray, 1821).
"The Arctic Ocean is also the area where the effect of climate change appears to be expressed the strongest. The current changes make the effort to identify the diversity of life in the three categories (sea ice, water column, and sea floor) harder. Changes in the environmental conditions will have different species level information; therefore it is essential to have discussions about climate change on their expressions and effects. These effects can be detected through only long-term monitoring of the key species, communities and the processes of the species. For monitoring and assessment of changes, the availability of baseline data is crucial. A lot of effects on the marine life on multiple levels, from populations to individuals" (Dr.Bodil Bluhm).
Climate change threatens the Arctic, changing it to an essentially ice-free environment during the summer, with ice-freeze up recurring only in the winter, and to a much lesser extent than recorded in history. The Arctic ice is a substrate for sea-ice dependent organisms, like phytoplankton and zoo-plankton, some crustaceans, seals and other organisms that feed on them, and the polar bears that feed on the seals (National Wildlife Foundation, 2001).
The entire Arctic food web is in danger from the most significant disruption with the disappearance of summer sea ice. With more open water and other climate factors, it would most likely benefit fish stocks like cod, herring, walleye, and pollock but it doesn't. The fish that have adapted to colder waters will have to consume more prey to sustain their increased metabolism mainly to keep the body temperatures up. The fish survival could be in jeopardy unless the available food source (plankton) increases in abundance but due to the warming waters, the plankton have yet to adapt. Other species native to warm waters may expand their range into the Arctic (Conlan, 2007).
Warmer sea temperatures have contributed abundantly to the reduction in herring populations in the Bering Sea near Alaska. This has led to a decline in the region's sea lions. Cold-water fish, such as cod and trout are being pushed further north into Canada, while warm-water species, such as smallmouth bass, are moving into northern U.S. waters as well. Since smallmouth bass are a predator to the cod and trout, it seems to be a constant battle, while other species are very dependent on the cold-water fish (Evans).
The commercial use of the Arctic cod is a major role in the reduction of the species. The Arctic cod are not at present harvested commercially by Canadian fishermen, although they are by Russian fishermen. The Arctic cod is a popular item in the Russian diet. Large numbers have been obtained off the Labrador Current by Russian trawlers (International Herald Tribune).
There are no current commercial harvests in the federal waters of the U.S. Arctic, which stretch from 3 to 200 miles offshore through the Chukchi and Beaufort Seas. Many believe that the amount of fish in those areas will increase in the years ahead if warming waters cause a migration of pollock and other species that now sustain major harvests farther south in the Bering Sea. As the Russians main source of employment is commercial fishing, this brings in a sum of $300 per pound of salmon alone. The liver oil from the Arctic cod is very expensive because cod liver oil is a popular nutritional supplement derived from the fatty tissues found in the livers of cod fish. Historically, cod liver oil has been a common supplement for children and now rapidly gaining popularity among adults of all ages, because it contains Omega-3 fatty acids, and vitamins A, D, and E all in one dosage (Tarascio, 1999-2009).
We should send a petition to the legislature to move polar bears onto the endangered species list, and make protecting them a law. This action has been resisted by past legislators for what ever political reason. However, if we move these creatures to the endangered list, it could created positive political PR for heads of state and other important representatives of Alaska and other Arctic regions, as well as create PR for the support of species protection.
Monitor the populations of polar bears, ringed seals, and the commercial fishing of Arctic cod. If we monitor these more closely we may be able to decrease the rate of decline of these populations. Make a greater push for the moving of polar bears onto the Endangered Species List. In the past our legislators have resisted this, but it's very important that we change this status. Also, monitoring and protecting a particular population of polar bears and the land they reside on from hunters and the like. By moving polar bears to the Endangered Species List, it will make the loss of them more public to other people in the world; this kind of PR could boost support of finding alternate sources of energy, and protection of endangered species. We should created a refuge or sanctuary in the Arctic, by creating this refuge the organisms that inhabit that area will be protected from oil drilling, hunters, and the like. By allowing the certain populations within to flourish it will allow positive increases in the surrounding community's populations.
In conclusions, as the primary contributors to global warming, we must try to stop global warming and prevent further destruction of the Arctic and the species inhabiting the Arctic, especially polar bears. Polar bears are the apex predator of the Arctic. If this species is lost the resulting consequences will be catastrophic to the Arctic food web. The collapse of this food web will have resounding negative influences on surrounding communities of Arctic animals, as well as humans.
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