Polar Bears
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--Nichole Hoskin 09:38, 2 July 2008 (EST)
Polar Bear Population Numbers
Polar bears are marine mammals, with their principle habitat is sea-ice and their main prey is other marine mammals.[1] Polar Bears primarily eat ringed seals, with “naive post-weaned juvenile ringed seals” forming “a high proportion of the annual energy intake of polar bears.”[2]
The distribution of polar bears appears to change with seasonal changes in the extent of sea-ice cover, since sea-ice cover provides access to ringed seals.[3] The distribution of polar bears also suggests an “apparent preferences for the more productive waters near shorelines, floe edge areas, and areas of persistent open water”, although, “polar bears occur throughout the polar basin, occasionally at latitudes >88◦N”.[4]
Polar bears are currently abundant and not threatened with extinction because of the implementation of the International Agreement for the Conservation of Polar Bears and their Habitat and the development of co-ordinated research and management programmes.[5] Scientists generally agree that improved conservation measures, primarily controls on harvests, have lead to an increase in polar bear numbers over the last 30 years.[6]
“The assertion that polar bears as a species are in imminent danger of extinction or even threatened with extinction in the foreseeable future is both unproven and unlikely.”[7]
Photo taken by Steve Amstrup on the pack ice in the Beaufort Sea, USFWS, December 5 2001, USFWS pictures of polar bears
Do Scientists know the size of polar bear populations?
“Estimates of the size of polar bear populations have relied largely on mark-recapture techniques (DeMaster et al. 1980, Stirling et al. 1980, Schweinsburg et al. 1982, Furnell and Schweinsburg 1984, Amstrup et al. 1986). However, accurate and precise estimates of population size are lacking because sample sizes are small due to logistic constraints imposed by studying an animal distributed at low density over large and often inaccessible areas.”[8]
“There are few places in the world where biologists would admit to not knowing whether a bear population was increasing, decreasing, or stable, yet the reality is that there are few places where we really do know for sure how bears are faring.”[9]
“Because most bear populations are of unknown size, a record of increasing known deaths is often taken as prima facie evidence of a population decline. Moreover, even poor records with no clear trend but occasional documentation of a surge of deaths may be cause to fear a population decline.”[10]
--Nichole Hoskin 09:02, 20 August 2008 (EST)
According to Secretary Kempthorne of the United States Department of Interior, “Although the population of bears has grown from a low of about 12,000 in the late 1960’s to approximately 25,000 today, our scientists advise me that computer modeling projects a significant population decline by the year 2050.”[11]
The Final Rule on the Listing of Polar Bears as threatened, under the Endangered Species Act (US), claims,
“The current status must be placed in perspective, however, as many populations were declining prior to 1973 due to severe overharvest. In the past, polar bears were harvested extensively throughout their range for the economic or trophy value of their pelts. In response to the population declines, five Arctic nations (Canada, Denmark on behalf of Greenland, Norway, Union of Soviet Socialist Republics, and the United States), recognized the polar bear as a significant resource and adopted an intergovernmental approach for the protection and conservation of the species and its habitat, the 1973 Agreement on the Conservation of Polar Bears (1973 Agreement). This agreement limited the use of polar bears for specific purposes, instructed the Parties to manage populations in accordance with sound conservation practices based on the best available scientific data, and called the range States to take appropriate action to protect the ecosystems upon which polar bears depend. In addition, Russia banned harvest in 1956, harvest quotas were established in Canada in 1968, and Norway banned hunting in 1973. With the passage of the MMPA in 1972, the United States banned sport hunting of polar bears and limited the hunt to Native people for subsistence purposes. As a result of these coordinated international efforts and harvest management leading to a reduction in harvest, polar bear numbers in some previously-depressed populations have grown during the past 30 years.”[12]
While the USFWS believes that polar bear numbers have increased with the introduction of international controls on harvesting limits, no published papers or reports support this view.
Effects of Climatic Fluctuations on Polar Bears in Greenland
In 1967, Dr Christian Vibe published an extended paper on the affect of climatic fluctuations, in Greenland, on animals such as polar bears, ringed seals, harp seals and others. Vibe demonstrated that climatic fluctuations changed the distribution of polar bears and ringed seals, with these animals moving to areas of more suitable habitat.
For more information, click here Effects of Climatic Fluctuations on Polar Bears in Greenland
Polar Bear Specialist Group of the IUCN Meetings
From 1965 on, the IUCN Survival Service Commission, Polar Bear Specialist Group held working meetings to enable polar bear experts to gather and discuss research on issues such as population numbers. The discussions of polar bear population numbers in 1965 and throughout the 1970s reveals that scientist were unable to gather sufficient data to estimate population numbers.
For more information, click here Polar Bear Specialist Group of the IUCN Meetings
IUCN Red List of Threatened Species listing of Polar Bears
--Nichole Hoskin 16:59, 7 August 2008 (EST)
Red List of Threatened Species:
The IUCN Red List of Threatened Species lists the Polar Bear (Ursus maritimus) as Vulnerable. According to the IUCN Red List, “there are 19 hypothesized subpopulations or stocks which number in total 20,000 to 25,000 bears. Considerable overlap of putative populations occurs and genetic differences among them are small.”[13] The population trend is downwards, according to the IUCN Red List.[14]
IUCN Summary Table for Polar Bear Population Status per 2005
U.S. Geological Survey Reports on Polar Bear Population Status in the U.S. and Canada
In order to make a decision on whether to list the Polar Bear as a threatened species, under the U.S. Endangered Species Act, the U.S. Fish and Wildlife Service (USFWS) asked the U.S. Geological Survey to report on scientific information about Polar Bear population status in the U.S. and Canada.
For more information, click here U.S. Geological Survey Reports on Polar Bear Population Status in the U.S. and Canada
Data on the Extent of Sea Ice in the Arctic Region
--Nichole Hoskin 11:31, 7 August 2008 (EST)
National Snow and Ice Data Centre, Colorado, Time Series of Sea Ice Extent
graph by Nichole Hoskin[15]
graph by Nichole Hoskin[16]
Listing of Polar Bears as Threatened under the US Endangered Species Act
The United States Department of Interior has listed the polar bear as threatened under the Endangered Species Act (US) because of the IPCC predictions that sea ice is likely to disappear in the arctic in about 45 years time.
For more information, click here Listing of Polar Bears as Threatened under the US Endangered Species Act
Campaigning
The World Wildlife Fund U.S. National Appeal mainly sponsored a summer expedition of the Norwegian polar bear scientists in the eastern Svalbard pack ice in August 1968.[17]
In 1972, the summary included a “placing on record IUCN's grateful thanks for the generous financial support accorded by the New York Zoological Society and by the American Conservation Association through the Conservation Foundation.”[18]
References
--Nichole Hoskin 11:43, 12 August 2008 (EST)
1. Dr Mitchell Taylor and Dr Martha Dowsley, Science & Public Policy Institute, Demographic and Ecological Perspectives on the Status of Polar Bears, p 6.
2. Dr Mitchell Taylor and Dr Martha Dowsley, Science & Public Policy Institute, Demographic and Ecological Perspectives on the Status of Polar Bears, p 8.
3. Dr Mitchell Taylor and Dr Martha Dowsley, Science & Public Policy Institute, Demographic and Ecological Perspectives on the Status of Polar Bears, p 6.
4. Dr Mitchell Taylor and Dr Martha Dowsley, Science & Public Policy Institute, Demographic and Ecological Perspectives on the Status of Polar Bears, p 6.
5. Dr Mitchell Taylor and Dr Martha Dowsley, Science & Public Policy Institute, Demographic and Ecological Perspectives on the Status of Polar Bears, p 5.
6. Dr Mitchell Taylor and Dr Martha Dowsley, Science & Public Policy Institute, Demographic and Ecological Perspectives on the Status of Polar Bears, p 5.
7. Dr Mitchell Taylor and Dr Martha Dowsley, Science & Public Policy Institute, Demographic and Ecological Perspectives on the Status of Polar Bears, p 5.
8. Andrew E. Derocher and Ian Stirling, ‘Estimation of Polar Bear Population Size and Survival in Western Hudson Bay’, Journal of Wildlife Management 59(2), p 215.
9. David L. Garshelis, ‘Misconceptions, Ironies and Uncertainties Regarding Trends in Bear Populations’, Ursus 2002 13, pp 321-322.
10. David L. Garshelis, ‘Misconceptions, Ironies and Uncertainties Regarding Trends in Bear Populations’, Ursus 2002 13, p 322.
11. United States Fish and Wildlife Service (USFWS), Remarks by Secretary Kempthorne at Press Conference on Polar Bear Listing, May 14 2008, p 4.
12. United States Fish and Wildlife Service (USFWS), Endangered and Threatened Wildlife and Plants; Determination of Threatened Status for the Polar Bear (Ursus maritimus) Throughout Its Range, Final Rule, p 96.
13. IUCN Red List of Threatened Species, IUCN Red List for Polar Bears (Ursus maritimus)
14. IUCN Red List of Threatened Species, IUCN Red List for Polar Bears (Ursus maritimus)
15. Arctic Climate Research at the University of Illinois, Seasonal Sea Ice Extent time series from 1870-2007
16. 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, p 21.
17. International Union for the Conservation of Nature and Natural Resources (IUCN), Proceedings of the 3rd Working Meeting of Polar Bear Specialists , February 7-10, 1972, p 16.
