Polar Bears and Climate Change, some Facts
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--Nichole Hoskin 14:29, 16 December 2008 (EST)
Related Links: Polar Bears Effects of Climatic Fluctuations on Polar Bears in Greenland Polar Bear Specialist Group of the IUCN Meetings U.S. Geological Survey Reports on Polar Bear Population Status in the U.S. and Canada Listing of Polar Bears as Threatened under the US Endangered Species Act
Contents |
Polar Bears and Climate Change
By Nichole Hoskin and Jennifer Marohasy
Polar Bears (Ursus maritimus) occur only in the Arctic Region, live on sea ice and eat mainly ringed seals.
They have become a symbol of climate change based on claims that global warming will cause higher temperatures in the Arctic and therefore reduced sea ice.
Since at least the 1980s, a period of over 20 years, the amount of sea ice has reduced, particularly in summer. However, most polar bear populations are stable or increasing.
Female polar bear with young, courtesy of the US Fish and Wildlife Service, photographed by Susanne Miller, Beaufort Sea Coastline of Alaska, October 15 2006.
History, Hunting and Inuit people
Inuit people have hunted polar bears for their furs for centuries.[1]
Inuit woman and child wearing polar bear fur leggings,
Photographed by Don Theye, Thule region, Greenland, 1951-1952
During the 19th and 20th Centuries, in Arctic areas of Greenland, Norway and Russia, the hunting of polar bears dramatically increased because of the use of firearms and more people living in these areas.[2]
In Canada, during the 1960s, the use of snowmobiles dramatically increased hunting of polar bears.[3]
International concern about increased hunting led to the development of the International Agreement for the Conservation of Polar Bears in 1973, also known as the Oslo Agreement.[4] Under this Agreement, States agreed to regulate the hunting of polar bears, although there are differences in the form of regulations in adopted by each state. The USSR banned hunting. Norway and Canada imposed quotas. The United States imposed quotas and restricted hunting to Inuit people. Greenland did not establish quotas until 2006.[5]
No accurate data on historic numbers
In the 1960s, the International Union for the Conservation of Nature and Natural Resources (IUCN) established the Polar Bear Specialist Group, which held meetings to improve knowledge of population numbers.[6]
Scientists attempted surveys by sight from aircraft and ships but found that it was difficult to see polar bears against white snow. The use of infra-red didn’t resolve this problem because the fur of polar bears reduces heat loss, making them undetectable.[7]
In the 1980s, the development of satellite tracked radio collars, fitted to female polar bears, enabled accurate estimates of numbers.[8]
Populations are stable, not declining
Polar bear numbers are currently estimated at between 20,000 and 25,000, and are not considered endangered.[9]
The Arctic Basin is a mixture of sea and ice floes. Most polar bears live in the Arctic Circle, on sea ice fixed to land in Canada, Alaska, Russia, Greenland and Norway. Canada has 60% of the world’s polar bears, including the most southern populations at western and southern Hudson Bay and Davis Strait.
There are 19 recognised discreet populations worldwide, with,
• 7 stable or increasing
• 5 declining
• 7 have insufficient data to enable estimates[10]
The Baffin Bay, Kane Basin and Norwegian Bay populations, in Greenland, are declining because of overhunting.[11]
Polar Bear Population Map, IUCN Polar Bear Specialist Group, 2008
(WH) western Hudson Bay (SH) southern Hudson Bay (DS) Davis Strait (FB) Foxe Basin (GB) Gulf of Boothia (MC) M’Clintock Channel (LS) Lancaster Sound (VM) Viscount Melville Sound (NB) Northern Beaufort Sea (SB) Southern Beaufort Sea (BB) Baffin Bay (KB) Kane Basin (NW) Norwegian Bay
Future Doom and Gloom
In 2005, the IUCN Red List of Threatened Species listed polar bears as vulnerable based on computer model predictions that numbers could decline by more than 30% by 2050.[12]
The United Nations Inter-Governmental Panel on Climate Change (IPCC) influential 2007 report on climate change predicted higher global temperatures and reduced amounts of Arctic sea ice, which could disappear in summer.[13]
Al Gore claims, in the book ‘An Inconvenient Truth’, that significant numbers of polar bears are already drowning because climate change is causing the melting of sea ice,
“The melting of the ice represents bad news for creatures like polar bears...for the first time, polar bears have been drowning in significant numbers. Such deaths have been rare in the past. But now, these bears find they have to swim much longer distances from floe to floe. In some places, the edge of the ice is 30 to 40 miles from the shore.”[14]
The United States Government announced the decision to list polar bears as threatened under the Endangered Species Act, in 2008, because of climate change predictions of reduced sea ice.[15]
Declines in Arctic Sea Ice
The amount of ice in the Arctic Circle has been measured since 1870, and over this period, has fluctuated from a low of 5.5 million km² to a peak of 16 million km².
The amount of sea ice varies seasonally with it melting in summer and the sea freezing in winter.
Since the 1970s, there has been a decline in sea ice, especially in summer. The lowest amount of sea ice occurred during the summer of 2007. But the annual average for 2007 was almost double the summer low, at 10 million km².
While there is less sea ice than has been common over the last 130 years, the decline in sea ice extent has not been as dramatic as is widely believed.
Historic seasonal sea ice extent data using seasonal averages to determine the annual mean
Winter (the mean of January, February and March)
Summer (the mean of July, August and September)[16]
Increasing Temperatures?
It is generally agreed that some global warming has occurred over the last 100 years, with the most warming occurring in the Arctic Circle. However, Arctic seasonal temperatures dramatically vary across years and in different regions, which means that long term temperature data is required to accurately determine trends.[17]
The world’s most studied polar bear population, at western Hudson Bay in subarctic Canada, is believed to be declining because of global warming. Churchill is in the area of this population, on the shores of Hudson Bay.
Thermometer temperature data, from 1885 to 2004, indicate that Churchill has been warmer since 1998. But the annual mean temperature is still below -4C˚ and there are 41 years without data.
Historic surface air temperatures data using monthly averages to determine the annual mean and excluding all years for which there is not an average for each month.[18]
In contrast, complete seasonal temperature data for Churchill, from 1932 to 2002, indicates that there is no warming trend.[19]
Churchill seasonal temperature graphs, from M.G Dyck, W. Soon, R.K. Baydack, D.R Legates, S. Baliunas, T.F Ball, L.O. Hancock, ‘Polar Bears of western Hudson Bay and climate change: Are warming spring air temperatures the “ultimate” survival control factor?’ Ecological Complexity (2007) 4, p 77.
Polar Bears Can Adapt to Changes in Climate
--Nichole Hoskin 10:25, 27 January 2009 (EST)
Popular perceptions are that warming threatens polar bears, which are largely based on speculation by Stirling and Smith (2004) that the long term consequences of global warming could include reduced amounts of ice and more rainfall during spring.[20]
These changes have been observed to cause the collapse of ringed seal birth liars and forcing juvenile ringed seals onto the ice where they are vulnerable to hunting polar bears.[21]
If fewer pups survive, this could lead to significant declines in ringed seal numbers and negative effects for polar bear reproduction and survival since ringed seals are the primary prey of polar bears.[22]
In contrast to these predictions, Dr Christian Vibe, the Representative for Denmark to the Polar Bear Specialist Group, told the 1970 meeting that it was possible that polar bears survived better during the warmer climates of the 1920s-1930s than in the 1960s, when a change in the climate caused colder winters in northern Arctic areas.[23] This change caused polar bears to move southwards to warmer areas, with the result that more bears drowned off scattered sea ice and come within the ranges of man. This movement suggests that polar bears will move to avoid colder winters and that climate is an important factor effecting the distribution of polar bears.[24]
Dr Christian Vibe, as printed in Jyllands-Posten, June 27 1998.
In Eastern Greenland, Dr Vibe found that the catch of polar bear and ringed seal furs increased from about 1890 to 1930, corresponding with an increase in East Greenland Ice, during May to August, based on ice data and records of furs purchased by the Royal Greenland Trade Department, from 1800 to the mid-1950s.[25] This suggests that fluctuations in climate are an important factor affecting the catch of polar bears.[26] (See graph below.)
Adapted from: Christian Vibe, ‘Arctic Animals in Relation to Climatic Fluctuations’,
in Meddelelser om Grønland (1967)
170(5), p 61.
Dr Vibe noted that polar bears moved when the Arctic climate fluctuated so that numbers in one location declined, with a corresponding increase in numbers at another location.[27]
The recent work of Danish polar bear expert, Rosing-Asvid, supports Vibe’s conclusions, while acknowledging that the long term consequences of warming could have negative effects for polar bear reproduction and survival.[28] Rosing-Asvid challenges the idea that warming causes polar bears to suffer in the short and medium terms by comparing official catch statistics, including Vibe’s data, from 1796 to 2003, and the ice index, from 1864 to 2005, which show that polar bear fur numbers increase and ringed seal fur numbers decreased during warmer climatic periods, with the opposite occurring during colder periods.[29] There is also evidence that polar bears initially benefit from warming because reduced ice makes it easier for them to hunt more ringed seals and harp, hooded and bearded seals.[30]
Research of the western Hudson Bay population found that, cub survival went from a low of just over 50%, in the late 1980s and early 1990s, to 70-80% in the late 1990s, according to Stirling, Lunn and Iacozza (1999).[31] This increase in cub survival occurred at the same time as a decline in the physical condition of adult polar bears, which is attributed to warming in the region.[32]
References
1. Christian Vibe, ‘Arctic Animals in Relation to Climatic Fluctuations’, (1967) Meddelelser om Grønland 170(5), p 61.
2. Wikipedia, Polar Bear Hunting
See also: A. Rosing-Asvid, ‘The influence of climate variability on polar bear and ringed seal population dynamics’, (2006) Canadian Journal of Zoology 84, pp 357-364.
3. Mitchell Taylor and Martha Dowsley, Demographic and Ecological Perspectives on the Status of Polar Bears, p 13.
4. Mitchell Taylor and Martha Dowsley, Demographic and Ecological Perspectives on the Status of Polar Bears, p 13.
See also: International Union for the Conservation of Nature and Natural Resources (IUCN), Proceedings of the 5th International Scientific Meeting on the Polar Bear, December 3-5, 1974.
5. International Union for the Conservation of Nature and Natural Resources (IUCN), Proceedings of the 5th International Scientific Meeting on the Polar Bear, December 3-5, 1974.
6. International Union for the Conservation of Nature and Natural Resources (IUCN), Proceedings of the 1st International Scientific Meeting on the Polar Bear, 1965.
7. International Union for the Conservation of Nature and Natural Resources (IUCN), Proceedings of the 2nd Working Meeting of Polar Bear Specialists , February 2-4, 1970
8. International Union for the Conservation of Nature and Natural Resources (IUCN), Proceedings of the 8th Working Meeting of Polar Bear Specialists, 1981.
9. IUCN Red List of Threatened Species, 2007, Polar Bears (Ursus maritimus)
10. IUCN Red List of Threatened Species, 2007, Polar Bears (Ursus maritimus)
11. IUCN Red List of Threatened Species, 2007, Polar Bears (Ursus maritimus)
12. IUCN Red List of Threatened Species, 2007, Polar Bears (Ursus maritimus)
13. Inter-Governmental Panel on Climate Change, Fourth Assessment Report, ‘The Physical Science Basis Report, 2007, Ch 3 and 4
14. Al Gore, An Inconvenient Truth: The planetary emergency of global warming and what we can do about it, Bloomsbury, 2006, p 147.
15. United States Fish and Wildlife Service (USFWS), Remarks by Secretary Kempthorne at Press Conference on Polar Bear Listing, May 14 2008, p 4.
16. Arctic Seasonal Sea Ice Extent, Arctic Climate Research at the University of Illinois
17. M.G Dyck, W. Soon, R.K. Baydack, D.R Legates, S. Baliunas, T.F Ball, L.O. Hancock, ‘Polar Bears of western Hudson Bay and climate change: Are warming spring air temperatures the “ultimate” survival control factor?’ (2007) Ecological Complexity 4, pp 77-78
18. Churchill surface air temperature, NASA Goddard Institute of Space Studies
19. M.G Dyck, W. Soon, R.K. Baydack, D.R Legates, S. Baliunas, T.F Ball, L.O. Hancock, ‘Polar Bears of western Hudson Bay and climate change: Are warming spring air temperatures the “ultimate” survival control factor?’ (2007) Ecological Complexity 4, pp 77-78
20. I. Stirling and T.G. Smith, ‘Implications of warm temperatures and an unusual rain event for the survival of ringed seals on the coast of southeastern Baffin Island’, (2004) Arctic 57(1), pp 59-67
21. I. Stirling and T.G. Smith, ‘Implications of warm temperatures and an unusual rain event for the survival of ringed seals on the coast of southeastern Baffin Island’, (2004) Arctic 57(1), pp 59-67
22. I. Stirling and T.G. Smith, ‘Implications of warm temperatures and an unusual rain event for the survival of ringed seals on the coast of southeastern Baffin Island’, (2004) Arctic 57(1), pp 59-67
23. International Union for the Conservation of Nature and Natural Resources (IUCN), Proceedings of the 2nd Working Meeting of Polar Bear Specialists , February 2-4, 1970, pp 15-16.
24. International Union for the Conservation of Nature and Natural Resources (IUCN), Proceedings of the 2nd Working Meeting of Polar Bear Specialists , February 2-4, 1970, pp 15-16.
25. Christian Vibe, ‘Arctic Animals in Relation to Climatic Fluctuations’, (1967) Meddelelser om Grønland 170(5), p 61.
26. Christian Vibe, ‘Arctic Animals in Relation to Climatic Fluctuations’, (1967) Meddelelser om Grønland 170(5), p 61.
27. Christian Vibe, ‘Arctic Animals in Relation to Climatic Fluctuations’, (1967) Meddelelser om Grønland 170(5), p 61.
28. A. Rosing-Asvid, ‘The influence of climate variability on polar bear and ringed seal population dynamics’, (2006) Canadian Journal of Zoology 84, pp 357-364.
29. A. Rosing-Asvid, ‘The influence of climate variability on polar bear and ringed seal population dynamics’, (2006) Canadian Journal of Zoology 84, pp 357-364.
30. A. Rosing-Asvid, ‘The influence of climate variability on polar bear and ringed seal population dynamics’, (2006) Canadian Journal of Zoology 84, pp 357-364.
31. I. Stirling, N.J. Lunn and J. Iacozza, ‘Long-term trends in the population ecology of polar bears in western Hudson Bay in relation to climate change’, (1999) Arctic 52(3), p 301.
32. I. Stirling, N.J. Lunn and J. Iacozza, ‘Long-term trends in the population ecology of polar bears in western Hudson Bay in relation to climate change’, (1999) Arctic 52(3), p 301.
