By Stephanie L. Swanson
The Arctic is a very unique ecosystem, having many characteristics that distinguish it from other systems found at mid and lower latitudes. The Arctic is a place like no other with its complete darkness in the winter, continuous daylight in the summer, frigid yearlong temperatures, extreme winters, and its widespread shelf seas located around the deep ocean basin. Although, its greatest distinguishing characteristic is the permanent ice cap that is composed of multiyear ice and first year ice that gets added each year. This Arctic sea ice reaches out over the vast ocean areas, extending and retreating seasonally as the weather changes.
With the increase in overall climate temperatures, the Arctic ecosystem is in peril. Warming in the Arctic is double to triple the overall global rate of 0.4°C. These escalations in Arctic temperatures can be seen in the rapid reduction and alteration in the Arctic sea ice. Arctic sea ice has been progressively decreasing since 1979. According to researchers, the area the ice covered has deteriorated from 16.5 million km² in 1979 to 15.25 million km² in 2009; that’s a decrease of approximately 45,000 km² per year. However, the sea ice is not only decreasing in area, but in thickness as well. In the past ten years alone, there has been a reduction of multiyear sea ice at triple the normal rate seen over the past three decades. A significant thinning of multiyear ice of approximately 0.6 m was seen between 2004 and 2008. Additionally, with the warming temperatures, there is a reduction in snow fall and the creation of first year ice. With the reduction of first year ice, there is nothing to counteract the loss of multiyear ice. What’s more, the sea ice is breaking up earlier in the year and freezing later, causing a longer period of open-water time within the Arctic. If the loss of sea ice continues on its current path, it is predicted that Arctic waters could be ice free in summers by 2035.
The loss of sea ice in the Arctic is significantly altering the habitat of Arctic marine mammals who have evolved to reside in the unique Arctic climate. Arctic marine mammals are highly specialized for the Arctic environment and dependent upon the sea ice for survival. Furthermore, these mammals are unequipped to quickly respond to the rapidly shifting ecosystem as a result of climate change. There are seven marine mammal species that call the Arctic home year round; four of which are ice-obligate species, meaning that they are completely reliant on sea ice platforms for their livelihood. Ice-obligate species, like the polar bear, are well adapted for life on sea ice, and this sea ice is crucial for all aspects of their lives. This dependency on sea ice makes ice-obligate species susceptible to changes in climate that results in the loss of sea ice, especially if this change is sudden and on a large scale.
Polar bears are categorized as marine mammals as their preferred habitat is Arctic sea ice. They are the world’s largest species of carnivore found on land, weighing in between 900 and 1,600 pounds and averaging in size between 7 and 8 feet from head to tail. These animals are well adapted for life on the Arctic sea ice, with thick fur and layer of blubber. This blubber provides insulation against the cold and buoyancy for aid in swimming. Additionally, they have large, oar-like, front feet and a streamlined neck and skull perfectly adapted for swimming in the Arctic. As a marine mammal, they spend almost all of their life upon the sea ice, and depend on it for hunting, mating, and traveling.
Polar bears reside throughout the Arctic’s ice covered seas. As one of the most ice dependent Arctic marine mammal and a top predator, the polar bear is a significant indicator of the health of the entire ecosystem. As the Arctic sea ice changes and recedes, it has a negative effect on certain populations and individual polar bears in the Arctic. These negative effects reach into all aspects of the polar bears life, movements, food availability, health and reproduction, and interactions with humans. Furthermore, longer traveling distances over rougher sea ice and through open water will greatly increase the chances of injury, sickness, and death.
Polar bears are known for their annual movement patterns within their individual home ranges, and these movements are dependent on the Arctic sea ice. While polar bears are capable of and adapted for swimming large distances, swimming takes more energy and they prefer to travel using sea ice. Furthermore, as Arctic temperatures continue to increase, it will continue to affect the sea ice. As a result, the ice will reduce in thickness and area, causing the ice to be more labile. This can cause the ice to fracture and sections of ice to break away from the main body of ice; polar bears on the ice when it fractures will be drifting away from their home range and it may result in a difficult trip to return. Past research reported such cases happening in Southwest Greenland and Newfoundland. With the loss of sea ice, polar bears are forced to land resulting in a decrease in the access of prey, mates, and denning areas.
Polar bears are also reliant upon the sea ice for foraging/hunting as they have developed an extreme specialization in prey. They rely on the availability and accessibility of ringed and bearded seals, their favored prey, for developing fat reserves. In the summer and autumn seasons, polar bears are cut off from their prey due to the loss of sea ice, consequently they must fast and relay on fat reserves for approximately four months until the ice expands again in the winter. Furthermore, female polar bears that are pregnant fast for up to 8 months because they remain on land for denning, birthing, nursing, and waiting for their cubs to grow large enough to travel safely onto the sea ice. However, with the warming temperatures, the ice is breaking up earlier and freezing later causing the length of fasting time for these bears to increase. In addition, the loss of sea ice during peak hunting seasons results in the polar bears inability to hunt seals. This is because polar bears do not capture their prey in open water. With the sea ice retreating further back, polar bears are unable to reach the seal pups that they feed on to gain the fat stores that carry them through their fasting periods. Recently, researchers have found that this lack of food availability has led to cannibalism within polar bear populations.
The collective effects of increased energy demands and the decrease in access to prey can lead to a decrease in body condition and other health related problems. With the shifts in prey and the amount of fasting time increased, the body condition of polar bears has been greatly affected. The premature break up of sea ice interrupts and shortens the polar bears feeding at the most crucial time of the year. Resulting in a poorer body condition before and during the seasonal fasting period. For the past three decades, researchers have seen a decline in the body condition of all ages of polar bears. This lower pre-fasting body condition leads to lower reproductive success, smaller litter sizes, and lower body conditions of both cubs and mother upon leaving the den. Overall, polar bears are free of parasites and rarely show signs of disease; however, lower body conditions will leave them more vulnerable to disease and parasites.
As the sea ice diminishes and food sources become scarce, polar bears venture inland often coming into contact with humans. In some locations, such as Hudson Bay, Foxe Basin, Baffin Bay, and Davis Strait, the sea ice completely melts causing the resident polar bear to spend months on land. Hungry and in search of food, these bears journey into human populated areas. This increase leads to an increase in human/bear conflict where ‘problem bears’, or bears that pose a risk to human life and/or property, are often killed.
In general, human-polar bear conflict occurs in one of three conditions: (1) polar bear(s) approach or wonder into human settlements, (2) polar bear(s) encounter humans working or camping in the tundra or on pack ice, and (3) people approaching polar bear(s) or their dens. The majority of human-polar bear conflict takes place when bears wonder into settlements, camps, and other human sites, where they raid food caches, damage property, attack dog and/or people, and overall endanger public safety. This may be due to food stressed/hungry bears being attracted to places where sled dogs are fed and housed, animals that were hunted for food get processed, and the remains of whale, seal, and caribou get discarded. Very rarely does human-polar bear conflict occur because the polar bear views humans as a food source. However, with the recent increase of ecotourism and Arctic research due to climate change, human-polar bear conflicts have increased, not only due to the influx of humans, but the lack of safety education and risk taking behavior.
Take Action
As a traveler or researcher, there are several actions one can take to insure the safety of both yourselves and the polar bears, while still enjoying all the Arctic has to offer. Be aware of your surroundings, do not take any unnecessary risks, and never approach a polar bear or their den. Before traveling, educate yourself on conflict prevention techniques and the laws regarding wildlife in the area in which you will be going. Keep all food items in bear proof containers and keep deterrence items, such as marine flares, cracker shells, bear bangers, and paper spray, with you during your travels. You can also help protect these animals from where you live by educating yourself on how the warming temperatures are impacting the Arctic ecosystem and how the loss of sea ice is impacting ice-obligate species. Easy steps taken at home, such as being energy-efficient, eating sustainable seafood, and minimizing consumption, can aide in slowing the loss of Arctic sea ice.
Stephanie Swanson is a conservationist and recent graduate of Miami University’s Project Dragonfly program; where she obtained a Masters in Conservation Biology. The focus of her studies is marine mammal awareness and conservation.
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