Melting Arctic Threatens Polar Bears
Two-thirds of the world's polar bears could vanish by 2050 as shrinking sea ice continues to reduce the bears' habitat, according to a recent report by U.S. government scientists. The study predicts that the bears will disappear completely from Alaska, Russia, and Norway, but cling on in smaller populations along the shores of Canadian Arctic islands and Greenland's northern coast.
In their report, scientists with the U.S. Geological Survey (USGS) in Alaska underscore the urgency of taking action now to reverse the effects of human-induced climate change. Without sea ice, polar bears are unable to hunt seals, the mainstay of their diet.
“As the sea ice goes, so goes the polar bear,” says Dr. Steven C. Amstrup, the project leader and a member of PBI's Scientific Advisory Council.
The USGS study was undertaken at the request of the U.S. Secretary of the Interior. The report will assist the U.S. Fish and Wildlife Service in determining whether to list the polar bear as a threatened species under the Endangered Species Act. That decision is due in January 2008.
Sea Ice Types
The USGS studies focused on four different types of sea ice habitats, or "ecoregions," used by polar bears. The team of scientists examined the current and projected sea ice conditions in each habitat. They then used available knowledge on the status of subpopulations within each ecoregion to make predictions for the entire habitat.
The four ecoregions include:
Habitats with Seasonal Ice – These occur at the southern extreme of the polar bear's range and include places like Canada's Hudson Bay, where the ice melts each summer and the bears are forced ashore to wait for the fall freeze-up.
Polar Basin Areas with Retreating Shoreline Ice – In these ecoregions, sea ice forms along the shore but then retreats, especially during the summer season.
Polar Basin Areas that Collect Shoreline Ice – Sea ice formed in other parts of the Arctic collects along the shore of these habitats, giving the bears access to seals.
Islands in the High Canadian Arctic – These islands are far enough north that sea ice remains along the coast even in summer, providing hunting for the bears.
The report stated that two-thirds of the world's polar bears live in habitats with seasonal ice or retreating shoreline ice—and that those populations are at the most risk. In those regions, the bears are likely to experience longer and longer waiting periods before the sea ice returns, eventually straining their ability to survive. "There's a limit to how long they can fast," Amstrup says.
USGS scientists predict that the bears will disappear from those regions within 45 years. Within 75 years, they will also vanish from polar basin regions that collect shoreline ice. Small groups of bears will continue to survive, however, along islands in the Canadian High Arctic and Greenland's northern coast.
Action Needed
Scientists who study climate change say that the rate at which the Arctic is melting is taking place at a faster pace than current models predicted. This past summer, the loss of sea ice increased ten-fold compared with the year before. In view of these rapid changes, the USGS report notes that its predictions are likely to be conservative.
Amstrup emphasizes that, despite this sobering news, time still remains to save the polar bear as a species. As pressures mount on the bears, it becomes more important than ever to document what is happening with each of the world's 19 polar bear populations. Conducting census counts in the Arctic is difficult and expensive, but hard data is necessary for the bears' survival—not only in terms of a wake-up call to the planet to curb carbon emissions, but also to ensure that remnant populations are granted protection from human activities.
"Our goal is to identify the geographic pockets where the bears survive and then work to help shield those areas from human activities until climate change can be reversed and the bears can repopulate the Arctic," says PBI's president, Robert Buchanan.
In their report, scientists with the U.S. Geological Survey (USGS) in Alaska underscore the urgency of taking action now to reverse the effects of human-induced climate change. Without sea ice, polar bears are unable to hunt seals, the mainstay of their diet.
“As the sea ice goes, so goes the polar bear,” says Dr. Steven C. Amstrup, the project leader and a member of PBI's Scientific Advisory Council.
The USGS study was undertaken at the request of the U.S. Secretary of the Interior. The report will assist the U.S. Fish and Wildlife Service in determining whether to list the polar bear as a threatened species under the Endangered Species Act. That decision is due in January 2008.
Sea Ice Types
The USGS studies focused on four different types of sea ice habitats, or "ecoregions," used by polar bears. The team of scientists examined the current and projected sea ice conditions in each habitat. They then used available knowledge on the status of subpopulations within each ecoregion to make predictions for the entire habitat.
The four ecoregions include:
Habitats with Seasonal Ice – These occur at the southern extreme of the polar bear's range and include places like Canada's Hudson Bay, where the ice melts each summer and the bears are forced ashore to wait for the fall freeze-up.
Polar Basin Areas with Retreating Shoreline Ice – In these ecoregions, sea ice forms along the shore but then retreats, especially during the summer season.
Polar Basin Areas that Collect Shoreline Ice – Sea ice formed in other parts of the Arctic collects along the shore of these habitats, giving the bears access to seals.
Islands in the High Canadian Arctic – These islands are far enough north that sea ice remains along the coast even in summer, providing hunting for the bears.
The report stated that two-thirds of the world's polar bears live in habitats with seasonal ice or retreating shoreline ice—and that those populations are at the most risk. In those regions, the bears are likely to experience longer and longer waiting periods before the sea ice returns, eventually straining their ability to survive. "There's a limit to how long they can fast," Amstrup says.
USGS scientists predict that the bears will disappear from those regions within 45 years. Within 75 years, they will also vanish from polar basin regions that collect shoreline ice. Small groups of bears will continue to survive, however, along islands in the Canadian High Arctic and Greenland's northern coast.
Action Needed
Scientists who study climate change say that the rate at which the Arctic is melting is taking place at a faster pace than current models predicted. This past summer, the loss of sea ice increased ten-fold compared with the year before. In view of these rapid changes, the USGS report notes that its predictions are likely to be conservative.
Amstrup emphasizes that, despite this sobering news, time still remains to save the polar bear as a species. As pressures mount on the bears, it becomes more important than ever to document what is happening with each of the world's 19 polar bear populations. Conducting census counts in the Arctic is difficult and expensive, but hard data is necessary for the bears' survival—not only in terms of a wake-up call to the planet to curb carbon emissions, but also to ensure that remnant populations are granted protection from human activities.
"Our goal is to identify the geographic pockets where the bears survive and then work to help shield those areas from human activities until climate change can be reversed and the bears can repopulate the Arctic," says PBI's president, Robert Buchanan.
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