The world’s largest land-living carnivore. Photo: Norwegian Polar Institute
Nearly 3000 polar bears on Svalbard and in the Barents Sea
The polar bear is the only of the world’s eight species of bears that is a pure carnivore, i.e. it only eats meat and blubber, mostly from seals. Hunting and migration patterns vary a lot between individuals. Some bears move through areas similar in size with the Norwegian mainland. Other bears, like many of the bears that have been tagged in Storfjorden, between Spitsbergen and Edgeøya, stay in that area and do not wander off into the Barents Sea.
The world population of polar bears are in the area 20 – 25 000 individuals. They are unevenly distributed throughout the Arctic. Satellitte tracking of the bears in the Barents Sea have told us that there is a joint Norwegian-Russian population around Svalbard and in the Barents Sea. This population was surveyed in 2004, and the resulting population estimate was nearly 3000 bears.
Dens have also been surveyed on Hopen and in some other traditionally important denning areas. The number of dens on Hopen appear to be fluctuating with the timing of the ice cover around Hopen in the autumn. If the ice cover appears later than usual, there will be fewer dens than it will be if the ice cover appears in early autumn. Due this apparent causal connection between denning and ice cover, the occurrence of dens is now permanently monitored on Svalbard.
Sea ice decline gives rise to concern
Due to variable environmental conditions in the Arctic, many biological systems also vary a lot. To monitor the impact of human activities is thus a challenge, because it is always important to distinguish between natural variation and variation caused by human activities.
The polar bear depends on sea ice, sea ice declines
Climate models predict a dramatic decline in sea ice cover during this century. Observations the last few years have shown a distinct and significant decline in the ice cover in almost all Arctic areas. It is a real chance that there will be no ice cover between Svalbard and the North Pole already the coming winter season.
In 2007 US Geological Survey published the results a forecast of sea ice and response of polar bear to a dramatic decline in the Arctic sea ice cover. These model runs showed that 2/3 of the world’s polar bears might be gone in 2050. Evidently, this remains to be seen, but there is general agreement among expertise that sea ice cover will continue to decline. The polar bear is totally dependent on sea ice to find food. Even more distressing is the fact that the polar bear’s most important prey species, the ringed seal an the bearded seal, are even more dependent on sea ice.
High levels of pollutants in polar bears
It has been documented that polar bear tissue contain high levels of some environmental pollutants, and some effects have also been documented. “Old” pollutants, like PCB and DDT, have been shown to decrease in the Arctic and in Arctic biota, polar bears included. But “new” pollutants, like brominated flame retardants and fluor compounds, are increasing.
Although it is extremely hard to document causal chains between a pollutant level and a defined effect in the animal, the measured levels of PCBs in polar bears in Svalbard are high enough that we have to expect effects like:
- hormone system disorders
- impaired immune defence
- impaired reproduction
- reduced lifespan
- increased cub mortality
Consequently this could lead to reduced survival and rapid reduction of population size due to diseases. We are at present however not able to predict with any level of confidence how the environmental pollutants finally will affect polar bear reproduction and population status.
Polar bears threatened by climate change and pollutants
Polar bears are top predators, and they are sensitive towards changes in the populations of prey species. Such changes will quickly be reflected by polar bear population status.
Climate change is the most serious threat to polar bears
Climate change means reduced sea ice coverage, delay in autumn ice formation and earlier spring ice melt. Consequently the polar bears must cope with a shortened hunting season, destruction of prime sea ice habitat, and it will also affect migration patterns and access to denning areas. Reduced snow quality from less access to good quality denning areas and a rise in average annual temperature might also affect the bears’ ability to build dens of acceptable quality.
Polar bears vulnerable to fat-soluble environmental pollutants
Polar bears eat seal blubber, which makes them vulnerable to fat-soluble environmental pollutants. The level of PCBs in polar bear tissues have been higher than in any other Arctic species. The levels measured in polar bears in Svalbard are also higher than those measured in polar bears in Canada and Alaska. New analyses suggest that polar bears in the eastern Barents and Kara Seas are the most polluted polar bears in the world, with Svalbard bears following close behind.
It is assumed that transport, dispersion and intake of organic pollutants and mercury in polar bears are affected by climate and climate change.
Most polar bear populations are hunted by inuit societies
Polar bears are protected throughout the Arctic. Nevertheless, most populations are hunted by inuit societies in Northern America, Greenland and Eastern Russia. All the hunt is regulated by quotas. Approximately 1000 bears are killed annually. Polar bears were protected in Svalbard in 1973, and since then there has been no polar bear hunt in Svalbard. There is some illegal hunt in northwestern Russia. The Svalbard/Barents Sea polar bear population might therefore be one of the last populations of a large predator in the world that is not hunted.
Increasing international focus
The international agreement on the conservation of polar bears was signed in 1973 by all the nations having polar bears: Denmark (Greenland), Canada, USA, Russia and Norway. The agreement prohibits any take (kills) of polar bears, apart from limited quotas to some native societies. It also regulates sale, import and export of hides and other products from killed polar bears. The agreement instructs the parties to run research and monitoring programs as a means to manage the population in the best possible manner.
In 2006 the World Conservation Union (IUCN) changed the polar bear red list status from Least Concern to Vulnerable (VU A3c). An analysis concluded that it was probable that the polar bear population could be reduced by 30 per cent or more in three generations (45 years). After this change in red list status some countries have changed their management and protection of polar bears accordingly. In Norway the polar bear is already fully protected. In USA the polar bear was given the status as threatened according to the Endangered Species Act in spring 2008.
The increased international focus on polar bears have made the countries behind the polar bear agreement decide to meet more often and regularly. They haven’t met since 1981, and at an informal meeting in 2007 they agreed to meet again regularly. The first meeting of the parties are planned for Tromsø in 2009.
Monitoring of the Barents Sea population
There are substantial research and monitoring activities centered around the joint Norwegian-Russian population in the Barents Sea. Population status are monitored through a mark-recapture program. In addition the research program aims to update the knowledge base on vital rates regularly.
About 230 females have been equipped with satellite transmitters since 1988. The results from this research give an overview of the polar bears’ habitat use. Analyses of blood and fat samples gives information on pollution status and genetics. Finally we monitor the sea ice conditions around Svalbard, to keep track of how climate change might change the polar bears’ living conditions.
The present monitoring regime on polar bears in the Barents Sea have given us an early warning on the potential stress from environmental pollutants. Whether this exposure affects the number of polar bears is impossible to know for certain at present. We need to carry out more aerial surveys, the next one is planned for 2009. Then we will be able for the first time to have some information on whether the number of polar bears in the Barents Sea are changing.