From Envirowiki

The polar bear (Ursus maritimus) is an endangered species living in the circumpolar north, the Arctic. They are endangered primarily because of human activity that is causing global warming. There are biological factors that make polar bears more susceptible to the adverse effects of global warming, including hunting habits and reproductive behavior. Other human activities such as pollution due to commercial industries, hunting for game, and oil/mining play a large role in the declining populations of polar bears. The primary concern is how we should approach the situation and what steps need to be taken to better understand our impacts on the habitat of these animals.

Contents 1 History & Adaptations 2 Declining Numbers 3 Threat of Climate Change 3.1 Impacts on Reproduction & Denning 4 Threat of Hunting/Harvesting 5 Threat of Pollution 6 Threat Oil Drilling & Mining 7 Threat of Hybridization 8 Conservation Summary 9 Conservation Methods 10 Carbon Dioxide Emissions & Global Warming 10.1 Transportation 10.2 Agriculture & Livestock 10.3 Deforestation 11 Solutions to Climate Change 12 Renewable Energy and Fuels 13 Community/Organizations 14 Policy 14.1 Cap and Trade 15 Conclusion 16 References

[edit] 1 History & Adaptations

The polar bear is a descendent of the brown bear that became isolated by glaciers in an area near Siberia and diverged while isolated from other populations roughly 200,000 years ago, during the Pleistocene [5]. The polar bear is superbly adapted to navigating the Arctic. They have undergone a series of evolutionary changes in order to survive in the unforgiving environment. Adult male polar bears weigh from 775 to more than 1,500 pounds [3]. Females are considerably smaller, normally weighing 330 to 550 pounds [3]. Each paw measures up to 12 inches, and the polar bear’s large paws help distribute the animal’s weight when it is treading on thin ice [5]. Polar bears have black footpads on the bottom of each paw. The pads are covered by small, soft bumps known as papillae, which help grip the ice and keep the bears from slipping. Polar bears are well-adapted to severe cold. A thick layer of blubber (up to 4.5 inches thick) provides them with excellent insulation, keeping their body temperature and metabolic rate at a constant [3]. Its high body fat also provides buoyancy when swimming. The polar bear’s compact ears and small tail also help prevent heat loss [5]. Other adaptations include a longer neck, useful in keeping the polar bear’s head above water when swimming, and warm, thick fur that is a light shade in order to help them blend in to their surrounding in order for them to effectively hunt for prey.

[edit] 2 Declining Numbers

There are an estimated 20,000 to 25,000 polar bears in the wild, and that number is rapidly declining [7]. The IUCN Polar Bear Specialist Group reclassified the polar bear as a vulnerable species on the IUCN’s Red List of Endangered Species at their most recent meeting (Seattle, 2005). Of the 19 subpopulations of polar bears, five are declining, five are stable, two are increasing, and seven reveal considerable uncertainty about the structure of these populations due to limited data [10]. On May 14, 2008, the U.S. Department of the Interior reclassified the polar bear as a Threatened Species under the Endangered Species Act, citing concerns about sea ice loss. Canada (home to over half of the global polar bear population) and Russia only list the polar bear as a species of concern [5]. The differences in status among the polar bear nations may arise because densities of polar bear populations differ in each location.

The five countries or “polar bear nations” where these remarkable creatures are found include the U.S. (Alaska), Canada, Russia, Denmark (Greenland), and Norway. Accounting for 70% of the global polar bear population, the thirteen North American subpopulations range from the Beaufort Sea south to the Hudson Bay and east to Baffin Bay [10]. One interesting fact is that DNA studies show that these polar bear subpopulations are not reproductively isolated [9]. This may be because polar bears are not territorial and their home range is immensely vast. This is a positive outcome because they are less prone to interbreeding and other genetic problems because they have a large gene pool.

[edit] 3 Threat of Climate Change

Climate change is the main threat to polar bears in modern times. The IPCC, the U.S. EPA, and the Arctic Climate Impact Assessment all report on the effect of global warming on declining sea ice [1]. The summer ice loss in the Arctic is now equal to an area the size of Alaska, Texas, and the state of Washington combined [1]! Scientists predict a mostly ice-free Arctic summer by 2040 if present trends continue. The IUCN now lists global warming as the most significant threat to the polar bear because diminishing sea ice directly affects polar bears, decreasing their hunting success and interfering with breeding [3].

Sea ice is critically important because polar bears use ice pack as a platform to hunt ringed seals, their primary food source. Ringed seals are the most numerous in the Arctic and along with other types of seals, are most commonly found on land-fast or solid ice where they rest and mate [1]. In winter, polar bears capture ringed seals by lying in wait by their breathing holes; a technique called still-hunting. Polar bears also stalk ringed seals when they’re basking on the ice. Life concentrates on the ice edge, where productive waters attract fish, birds and mammals, providing a web of interactions and food for many animals [1]. Hence, the ice edge is critical feeding habitat for polar bears.

Most terrestrial animals in the Arctic can outrun the polar bear, and polar bears overheat quickly when running. Most marine animals can also out swim polar bears, and so polar bears feeding success depends on hunting on ice pack. These large carnivores have been observed eating a wide variety of food, including musk ox, reindeer, birds, eggs, rodents, shellfish, and even other polar bears [2]. Polar bears have also been known to prey on beluga whales, along with dead walrus and whale carcasses [11]. Polar bears may resort to scavenging or turning to cannibalism because of scarce food sources.

[edit] 3.1 Impacts on Reproduction & Denning

Polar bears congregate in the best seal hunting areas, and courtship and mating take place on the sea ice in spring. Most female polar bears mate at the age of four or five and some have cubs until they are 25 years old [3]. Polar bears have a polygynous mating system, and each litter typically consists of two cubs. Cubs are born helpless and nurse for two and a half years [13]. The fragile polar bear population is strained by low birth rate numbers and cubs take longer to reach sexual maturity. Cubs face additional obstacles because they may fall prey to wolves, to adult male polar bears, or to starvation.

Polar bears do not usually hibernate, and only pregnant females hold up in a den. The rest of the population remains active throughout the year. Pregnant female polar bears den up in the fall after feeding heavily. Most choose den sites in snowdrifts along mountain slopes or hills near the sea ice. Others den in the banks of snow on the frozen sea [5]. Populations are showing signs of stress due to their shrinking habitat.

[edit] 4 Threat of Hunting/Harvesting

In the 1960’s and 1970’s, hunting was the major threat to polar bears. Wealthy men had taken to hunting bears in Alaska from airplanes [3]. Its only purpose was to obtain the bear’s fur as a trophy for the floor or wall of someone’s den [3]. The traditionally important cultural activity of hunting polar bears by indigenous people also contributes to the decline of local populations. Legal hunting continues to kill more than 700 polar bears a year [3]. Inaccurate population surveys and the lack of data in the past have allowed hunting quotas to be set dangerously high. Today, many of the five main polar bear countries set restrictions and quotas to protect polar bears from being overexploited.

[edit] 5 Threat of Pollution

The most detrimental and best studied chemical that poses significant problems to polar bears is Polychlorinated Biphenyl (PCB). PCB is used in hundred of industrial and commercial applications throughout the world and it enters oceans, making its way up the food chain, into polar bears. High levels of PCB can weaken the polar bear’s immune system, leading to greater susceptibility to parasites and disease [12]. The effects of this synthetic poison have been correlated to reproduction failure and malformed organs [12].

[edit] 6 Threat Oil Drilling & Mining

The potential threat of oil drilling and mining is most concerning when looking at oil spills. Polar bears rely on their fur for insulation and oil reduces the effectiveness. Polar bears soiled by oil are at risk of dying from hypothermia. Polar bears exposed to oil spills are also prone to licking their fur, leading to poisoning and kidney failure [12].

[edit] 7 Threat of Hybridization

Hybridization is a threat to polar bear populations. Polar bears can breed with brown bears to produce fertile grizzly-polar bear hybrids, indicating that they have only recently diverged and are genetically similar [8]. As a result of declining ice, polar bears are spending more time on land and grizzly bears are venturing further north. Hybridizing is a risk to the polar bear species because there may be genetic issues to cross-breeding or polar bears could eventually be out bred due to their limited numbers [4]. Grizzlies also could pose as competition for prey, and polar bear cubs could be at risk of being eaten. The polar bear has unique adaptations to thrive in its habitat, and hybridization could result in the loss of those adaptations, leading to their extinction.

[edit] 8 Conservation Summary

Polar bears are the world’s largest land predators and they have an enormous ecological role in the Arctic region. It is known that the relationship between ringed seals and polar bears is so close that they regulate each others density in highly populated locations. Polar bears also play a role in other relationships. For example, the Arctic fox relies on the left over carcasses of polar bear prey for food. Polar bears only eat the blubber of seals when food in plentiful, leaving meat for foxes and birds [2]. Large carnivores like polar bears, are also sensitive indicators of ecosystem health [7]. Larger mammals are also the first to feel negative consequences of human “ecological footprint”.

[edit] 9 Conservation Methods

Polar bears face great peril in the 21st century; primarily due to the effects of climate change. Only collective action across the globe will be able to save them. Methods of conservation and how we should approach this issue will be discussed.

[edit] 10 Carbon Dioxide Emissions & Global Warming

The atmosphere’s concentration of carbon dioxide (CO2) has increased by more than 30 percent over the last 250 years, largely due to human activity. Two-thirds of that rise has occurred in the past 50 years [15]. Immediate action is necessary to slow down the trend of global warming, or polar bears will become extinct. There are technologies and strategies to reduce carbon emissions, including energy conservation methods, renewable energy and fuels, and governmental policies. There are also actions that need to be taken on an individual level in order to raise awareness and make a change.

[edit] 10.1 Transportation

One-eighth of all global emissions come from light-duty vehicles- cars, vans, sports utility vehicles (SUVs), and light trucks [15]. A recent study by the Sustainable Mobility Project (SMP), reports that the world’s light-duty vehicles emitted 0.8 billion tons of carbon as CO2 in 2000. SMP predicts that these emissions will double in 2050, to 1.6 billions tons of carbon per year [15]. There has been increasing research and demand in hybrid vehicles in recent years due to rising oil prices. Tesla Motors has created a sports car that runs on 100 percent battery power (teslamotors.com). Although hybrid vehicles may eventually help reduce carbon emissions, it alone is not sufficient. Internal combustion engines are terribly inefficient. They only convert less than 20 percent of energy from gasoline and the rest is lost out the exhaust pipes. Car engines cannot harness all the thermal energy and it is wasted (howthingswork.com). Carpooling and using public transportation are also more environmentally friendly methods of action. Living efficiently is the first step to energy conservation.

[edit] 10.2 Agriculture & Livestock

Agriculture and livestock are significant contributors to the net release of carbon. The net additions of carbon to the atmosphere are estimated at between 4.5 and 6.5 billion tons per year [18]. Mostly due to the burning of fossil fuel and land-use changes. Methane from livestock makes up only a very small part of the net release of carbon. Much more carbon is released indirectly by other channels of agriculture and livestock including [18]:

• Burning fossil fuel to produce mineral fertilizers used in feed production;
• Methane release from the breakdown of fertilizers and from animal manure;
• Land-use changes for feed production and for grazing;
• Land degredation;
• Fossil fuel use during feed and animal production; fossil fuel use in production and transport of processed animal products.

[edit] 10.3 Deforestation

Deforestation contributes to carbon emissions in another way because it destroys natural sinks in our environment. The main natural sinks are absorption of carbon dioxide by the oceans, and photosynthesis by plants (trees) and algae. Trees are a natural way to compensate for carbon emissions but deforestation due to development and land-clearing for agricultural use is destroying the relationship. Current deforestation is transferring carbon from forests to the atmosphere at a rate of approximately one billion tons of carbon per year [15]. This is a serious problem that is projected to increase over the next 50 years.

[edit] 11 Solutions to Climate Change

Energy conservation is the initial step to reducing present trends of carbon emissions. Energy conservation is of first importance because individuals can make a significant impact. Global C02 emissions come from three broad end-use sectors: power generation (42 percent), transportation (22 percent), and direct uses of fuel in industry and buildings (36 percent) [15]. We also need to take action in lowering carbon emissions by revising agriculture and livestock systems and reduce CO2 loss via deforestation. There are opportunities everywhere to conserve power; in power plants and household appliances, in airplane engines and city planning, in steel mills and materials recycling. All three sectors must become targets of more intense efforts to improve energy efficiency in order to reduce carbon.

[edit] 12 Renewable Energy and Fuels

To further reduce carbon emissions, a more drastic approach to how we create and use energy is imperative. Renewable energy is energy generated from natural resources- such as wind, sunlight, rivers, and geothermal heat- which are renewable (naturally replenishing). The introduction of renewable energy can reduce carbon emissions from power plants and other areas where fuels are directly used. Electricity can be produced by many renewable energy sources. Hydropower was the first renewable energy source to gain a large market share [15]. Energy in water (in the form of kinetic energy) can be harnessed and used. Since water is about 800 times denser than air, even a slow flowing stream of water can yield considerable amounts of energy. Wind power has been growing globally for the past decade at about 30 percent per year. Airflow can be used to run wind turbines. Modern wind turbines range from around 600 KW to 5 MW of rated power [16]. A wind farm, when installed on agricultural land, has one of the lowest environmental impacts of all energy sources. Solar energy refers to energy that is collected from sunlight. Solar energy can be applied in many ways, including generating electricity using photovoltaic solar cells. Solar photovoltaic electricity (PV), from a much smaller base, is also growing 30 percent per year globally [15]. Geothermal energy is energy obtained by tapping the heat of the earth itself, usually from kilometers deep into the Earth's crust. It is expensive to build a power station but operating costs are low resulting in low energy costs for suitable sites. Ultimately, this energy derives from heat in the Earth's core.

Renewable fuels are another option for reducing carbon emissions. Plants use photosynthesis to grow and produce biomass. Also known as biomatter, biomass can be used directly as fuel or to produce biofuels. Agriculturally produced biomass fuels, such as biodiesel, ethanol and bagasse (often a by-product of sugar cane cultivation) can be burned in internal combustion engines or boilers [15].

[edit] 13 Community/Organizations

Many organizations and citizens are fighting to save wild species, and in addition to slowing or reversing the rate of climate change, these efforts may be critical to helping prevent extinction of polar bears. Earth Hour [earthhour.org] is a worldwide event where people turn off their lights for one hour, in order to conserve energy and make a statement. Other organizations such as the World Wildlife Fund make efforts to:

• Research how global warming affects the long-term condition of polar bears
• Work to reduce GHG emissions and mitigate climate change
• Protect critical habitat
• Prevent or remove industrial activity
• Promote sustainable consumptive and non-consumptive use of polar bears

[edit] 14 Policy

Governmental policies are important in creating an infrastructure to reducing carbon emissions. The Kyoto Protocol is a 1997 international treaty which came into force in 2005, which binds most developed nations to a cap and trade system for the six major greenhouse gases [14]. The treaty is intended to achieve stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous climate change. As of 2008, 183 parties have ratified the protocol. Under Kyoto, industrialized countries agreed to reduce their collective GHG emissions by 5.2% compared to the year 1990 [14]. Kyoto includes defined "flexible mechanisms" such as emissions trading, a governmental plan to create economic incentives to reduce carbon emissions.

[edit] 14.1 Cap and Trade

Two prominent approaches to achieve greenhouse gas reductions is the traditional command-and-control regulation, in which regulatory authorities (the government) direct how emissions limits will be achieved, and market-based approaches, which harness the forces of supply and demand to change behavior and encourage environmental goals [17]. Cap and trade is one proven market-based approach. It's possible for a country to reduce emissions using a command-control approach, such as regulation, direct and indirect taxes. But that approach is more costly for some countries than for others. In a cap-and-trade program, the government determines which facilities or emissions are covered by the program and sets and overall emission target, or “cap”. This cap is the sum of all allowed emissions from all included facilities. Once the cap has been set, tradable emissions allowances (rights to emit) are distributed (either auctioned or freely allocated) [17]. Facilities are encouraged to reduce there emissions because these allowances are essential money. The less carbon they emit, the more “cap room” they can sell off to other facilities. It is a cost effective way to encourage environmental goals while giving these companies an economic incentive.

[edit] 15 Conclusion

All of these actions are ways to reduce carbon emissions and fight the present trend of global warming. Without these conservation strategies or policies, polar bears will become extinct. Awareness is the key to saving our environment and individuals as well as policy makers all have a part in making the change.

[edit] 16 References

[1] Kister, Chad. Arctic Melting. Monroe, ME: First Printing, 2005.

[2] Young, Steven. To The Arctic. New York: Wiley Science Editions, 1989.

[3] "Polar Bears and Global Warming." Polar Bears Global Warming - Effects of Global Warming 28 Jan 2009 <http://www.bearplanet.org/global-warming-polar-bears.shtml>.

[4] Rollins, Fiona. "Grizzlies Invade Polar Bear Turf." National Wildlife vol. 43 no. 3Apr/May 2005 30 Jan 2009 <http://www.nwf.org/nationalwildlife/article.cfm?issueID=74&articleId=1071>.

[5] "Polar Bears and Conservation." Bear Facts. Polar Bears International. 30 Jan 2009 <http://www.polarbearsinternational.org/polarbear/>.

[6] "SAVING THE POLAR BEAR." Mammals - Polar Bear. Center for Biological Diversity. 1 Feb 2009 <http://www.biologicaldiversity.org/species/mammals/polar_bear/>.

[7] "WWF: A Leader in Polar Bear Conservation." WWF: Polar Bear. World Wild Life. 30 Jan 2009 <http://www.worldwildlife.org/species/finder/polarbear/polarbear.html>.

[8] Schliebe, Scott. "Range Wide Status Review of the Polar Bear." U.S. Fish and Wildlife Service Dec. 21, 2006 3 Feb 2009 <http://alaska.fws.gov/fisheries/mmm/polarbear/pdf/Polar_Bear_%20Status_Assessment.pdf>.

[9] Rice, Dale W. (1998), Marine Mammals of the World: Systematics and Distribution, Special Publications of the Society for Marine Mammals

[10] Gunderson, Aren (2007). "Ursus Maritimus". Animal Diversity Web. University of Michigan Museum of Zoology. 3 Feb 2009 <http://animaldiversity.ummz.umich.edu/site/accounts/information/Ursus_maritimus.html.>

[11] Clarkson, Peter. Polar Bears. Renewable Resources Government of the N.W.T. 2 Feb 2009 <http://icwdm.org/handbook/carnivor/ca_c25.pdf>

[12] "Landward and eastward shift of Alaskan polar bear denning associated with recent sea ice changes", Polar Biology <http://www.springerlink.com/content/q111nx0106vv0137/>

[13] Stirling, Ian (1988). "Reproduction". Polar Bears. Ann Arbor: University of Michigan Press.

[14] Toman, Michael. Climate Change Economics and Policy. Washington D.C.: RFF Press Book, 2001.

[15] Socolow, Robert, Hotinski Roberta, Greenblatt Jeffery, and Pacala Stephen. "Solving the Climate Problem." <http://www.princeton.edu/~cmi/resources/CMI_Resources_new_files/Environ_08-21a.pdf>

[16] "Wind Energy - The Facts." 5 Mar 2009 <http://www.ewea.org/fileadmin/ewea_documents/documents/publications/WETF/Facts_Summary.pdf>.

[17] 3. "Cap and Trade." Climate Change 101. PEW. 17 Feb 2009 <http://www.pewclimate.org/docUploads/Cap&Trade.pdf>.

[18] "Livestock's Long Shadow." FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS 11 Mar 2009 <http://www.fao.org/docrep/010/a0701e/a0701e00.HTM>.

[19] "Ursus Maritimus." Red List. IUCN. 5 Mar 2009 <http://www.iucnredlist.org/details/22823>.