Polar bears are well adapted to cope with little to no food during short period of time by fasting (Watts and Hansen 1987). However, how well would this bear species fair if the time was extended due to being stranded on land? The polar bear became vulnerable in 1982 and the INCU stated ‘The assessment is based on a suspected population reduction of >30% within three generations (45 years) due to decline in area of occupancy (AOO), extent of occurrence (EOO) and habitat quality.’ This means within 45 years, there will be a 30% decrease in the population of polar bears. Ice cover is key to the bears movement in the Arctic, where they have to move to breeding areas, feeding areas and denning areas.
In figure 1 you can see the predictions for ice concentration, ice thickness and snow depth are significantly lower than the levels of today. This shows that the time period of the maximum will become narrower and this will reduce the time bears will be able to spend on the ice sheets before having to return to land. By 2099, this model predicts there will be a 2-4 month period of an ice-free Arctic. The ice thickness will roughly half in each area by 2099 and this will cause a reduction in the hunting season due to unstable ice. When bears are isolated on land for long periods of time, in a few cases they have been observed to pursuit reindeer and even consume nestling sea birds (Stempniewicz et al., 2013). The seals which the bears feed on may also be affected by the warming climate. This change in temperature may bring rainfall which will collapse the roofs of many seal dens, exposing the pups and allowing polar bears and arctic foxes to kill and eat them (Stirling, 1993). Over time this will lead to a decrease in the population, and therefore a reduction in food supply for the polar bears.
Numbers of dens made on pack ice are decreasing due to the reduction in stability on the ice shelf. From 1985-2004, Fischbach carried out a study on 89 pregnant females which had been collared. Dens made on pack ice had reduced from 62% down to 37% between these years and he concluded this was due to the melt season becoming longer and thus reducing the amount of stable old ice and impacting the formation of new ice.
As the Arctic climate warms and the ice sheets decrease, there is an influx of companies waiting to exploit the untouched resources, such as oil, gas and minerals, all of which may alter the habitat and the natural landscape. Polar bears may have to change migration routes to avoid these activities and their may be more frequent human encounters, which could lead to bear attacks or killing of bears in self defence. Oil spills may cause the fish and seal population to suffer and in turn, the polar bears will too be affected.
There is an agreement between the major Arctic countries Russia, Canada, Greenland, Norway and the US, signed in 1973. The ‘Agreement on the conservation of polar bears’ was brought in to decrease the severe hunting of bears in the Arctic in 1960s and 70s. The treaty prevents unregulated hunting of polar bears and agrees for the country to protect the environment, especially where they feed, migrate and den. Countries must also prevent the trafficking and exportation of bears, fur and trophy pieces. This is one of the original and most successful agreement and countries meet every three to four year to discuss research and conservation progress.