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Klima 6-2008

Opinion: Is the polar bear threatened by climate change?

Can the polar bear adapt to climate change and survive as a species, as Bjørn Lomborg suggests in his latest book, "Cool It"?

Perhaps blueberries, roots and the occasional sheep rather than seal will become the polar bear’s diet if the sea ice disappears? And why can’t the polar bear hibernate in anthills and windfalls on land as well, just as its relative the brown bear does?

Different lifestyle and biology

In his latest book, "Cool It", Bjørn Lomborg goes beyond suggesting that the polar bear can survive as a species by switching over to the biology of the brown bear if its habitat on the ice in the Arctic Ocean should disappear. He even cites the scientific report Arctic Climate Impact Assessment (ACIA 2004) in support of his speculations. It is a complete misunderstanding of the text. The authors of the cited chapter in ACIA say that it is difficult to envisage the polar bear surviving as a species if the ice disappears. For most biologists and others who know these two species well, it is absurd to think that the polar bear would be able to acquire the brown bear’s lifestyle and biology within the time perspective in question here. Brown bears - the same species as grizzly bears - and polar bears are two different species. They have widely different habitats and biology. While the brown bear is an omnivore and generalist, the polar bear is much more of a predator and a specialist in hunting seals on the ice. If the ice disappears, the polar bear will not be able to survive as a species.

Two extremes

But this is not Lomborg’s main point. He claims that the world’s polar bear population is currently viable and growing. According to him, it even seems to grow most where it has become warmest. Climate change poses no threat to the species. We have seen a few Norwegian biologists resort to simplistic arguments of this kind in the newspapers. Lomborg believes that we can learn three things from the polar bear story: it illustrates the powerful and exaggerated claims about the consequences of climate change that are not supported by scientific facts; there are many such stories; and our concerns make us focus on the wrong solutions. He uses this, together with other examples, to support the book’s main message that we must adapt to rather than fight climate change.
 
While Lomborg trivializes, others go to the other extreme. The World Wildlife Fund has suggested that polar bears could already be extinct by 2012, and Al Gore says in his film that polar bears are already drowning in significant numbers because the sea ice is disappearing. The story of drowning polar bears has become an urban legend. And who can forget one of the covers of "Time" magazine last year with a lonely polar bear on an isolated ice floe that illustrated a major article on climate change - an article that many characterized as a turning point in the climate debate?

Research-based knowledge

What does the research say about the polar bear and climate change? The International Polar Bear Specialist Group is established to, among other things, advise the partners of the International Polar Bear Convention in which five countries are members (Canada, Denmark, Norway, Russia and the U.S.A.). It gathers together virtually all active polar bear researchers. Already in 2005, the group unanimously recommended that the Red Listing, i.e. how vulnerable or endangered a species is, of the polar bear should be upgraded from "Near Threatened" to the "Vulnerable" category (pbsg.npolar.no). The justification for that was based on an evaluated probability of a decline in population of more than 30 percent within the next 35-50 years, caused mainly by the negative effects of climate change on sea ice and a possible additional effect of pollutants in a few areas. After scrupulous review, both the USA and Norway complied with the recommendation.
 
The Polar Bear Specialist Group has not taken its evaluations completely out of thin air. They are based on published scientific works which all conclude that polar bears will be in serious difficulty if their habitats are further reduced (see e.g. Regher, et al, 2007, Stirling and Parkinson 2006, Laidre, et al, 2008). As far as I know, there are no scientific publications which conclude otherwise. Even now, it is well documented that certain populations of polar bears are negatively affected by climate change. Moreover, widespread reductions of sea ice in the last two years have come as a surprise to ice researchers and likely reinforced the threats to the polar bear from climate change.

The polar bear is vulnerable

There is hence no basis in the research to suggest that the polar bear may be extinct by 2012, but neither is there a reason to brush aside the polar bear as a symbol for the consequences of climate change. Although the current population is viable and comprises 20 000 to 25 000 individual animals, it is in full conformity with both existing research and with the practice and criteria for the Red Listing of species to categorize the polar bear as vulnerable to climate change. This fact, and the research it is based on, is left out by Lomborg when he tells the polar bear story. Unfortunately, this is just one example of a pronounced selective use of references and incorrect interpretations that recur throughout the book.
 
There is also an amount of scientific substance to the drowning polar bears story. Monnett and Gleason (2006) observed drowning polar bears off the coast of Alaska in a year when the ice was far to the North and there is speculation that this type of mortality will increase as the ice disappears, leading to larger areas in the Arctic Ocean with open water.
 
We must also remember that the polar bear is part of a distinct ecological system comprising several hundred species of animals and plants (algae) associated with the ice. Many of these species will hardly be able to survive without the ice as their habitat. For us humans, the Arctic sea ice seems like one of the most inhospitable environments on Earth. It arouses astonishment when it turns out that it is full of life. A walk on the ice in April/May when the resurgence of the algae is at its most intense, with the sun shining constantly and a myriad of seabirds and marine mammals feeding on a soup of crustaceans in the ice-holes, is one of the most fascinating things one can do in the Arctic. When this ecological system is affected by us in a negative way, there is every reason to take it seriously and base our actions on scientific knowledge.
 
Translation by Hon Khiam Leong

References

  • Laidre, K.L., Stirling I., Lowry L.F., Wiig Ø., Heide-Jørgensen M.P., and Ferguson S.H. 2008. Quantifying the sensitivity of arctic marine mammals to climate-induced habitat change. Ecological Applications 18: 97-125
  • Monnett, C., and Gleason J.F. 2006. Observations of mortality associated with extended open-water swimming by polar bears in the Alaskan Beaufort Sea. Polar Biology 29: 681-687
  • Regehr E.V., Lunn N.J., Amstrup S.C., and Stirling I. 2007. Survival and population size of polar bears in western Hudson Bay in relation to earlier sea ice breakup. Journal of Wildlife Management 71: 2673-2683.
  • Stirling I. and Parkinson C.L. 2006. Possible effects of climate warming on selected populations of polar bears (Ursus maritimus) in the Canadian Arctic. Arctic 59: 261-275.

 

Last updated: 30.06.2009

VULNERABLE? The International Polar Bear Specialist Group gathers together virtually all active polar bear researchers, and it has recommended already in 2005 to categorize the polar bear as vulnerable. Significant reductions in sea ice during the last two years have likely reinforced climate threats to the polar bear, writes the article author, seen here with a polar bear cub. The picture was taken in 1980, and is from Svenskeøya on Svalbard. Photo: Birger Amundsen.VULNERABLE? The International Polar Bear Specialist Group gathers together virtually all active polar bear researchers, and it has recommended already in 2005 to categorize the polar bear as vulnerable. Significant reductions in sea ice during the last two years have likely reinforced climate threats to the polar bear, writes the article author, seen here with a polar bear cub. The picture was taken in 1980, and is from Svenskeøya on Svalbard. Photo: Birger Amundsen.
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