Global Warming Threatens Walrus

The polar bear has received the most attention relative to the plight of endangered species in the Arctic, but many other mammals, like the Pacific walrus, are believed to be threatened by the loss of sea ice as well.

Global warming will make many species endangered, as heat-intolerant species struggle to find suitable habitat, new diseases spread and the ecology of vast regions changes.

Photo: NOAA

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The Pacific walrus is facing extinction due to global warming and oil and gas development and should be protected by the Endangered Species Act.

That's the position of the Center for Biological Diversity, which filed a legal petition with the Fish and Wildlife Service that contains scientific data the group says backs up its claim.

“The Arctic is in crisis from global warming. Arctic sea ice is disappearing at a stunning rate that vastly exceeds the predictions of the best climate models,” said Shaye Wolf, a biologist with the Center for Biological Diversity and lead author of the petition. “The Pacific walrus is an early victim of our failure to address global warming. As the sea ice recedes, so does the future of the Pacific walrus.”

The Pacific walrus is a well-known resident of the Arctic seas between Alaska and Siberia whose existence, like that of the polar bear, is intimately linked with the sea ice. The walrus, whose scientific name means “tooth walking sea horse,” uses the sea ice as a platform from which to forage for clams and mussels in the relatively shallow waters over the continental shelf. A walrus can consume as many as 6,000 clams in a single multi-hour foraging session. Female walruses and their calves follow the sea ice year-round and rely on the safety of ice floes for nursing their calves and as essential resting platforms between foraging bouts since they cannot continually swim. All Pacific walrus are dependent on sea ice for their breeding activities in winter.

However, this sea ice is rapidly shrinking and forcing the Pacific walrus into a land-based existence for which it is not adapted. In 2007, the early disappearance of summer sea ice pushed females and calves onto land in abnormally dense herds. As a result, females and young were forced to abandon large regions of their at-sea feeding grounds, and calves suffered high mortality on land due to trampling by the dense herds. Walrus calves, unable to swim as long as adults, have also been abandoned by their mothers at sea, which has been attributed to the disappearance of the sea ice on which they would normally rest.

The impacts of global warming on the Pacific walrus will worsen in this century, according to the group. One scientist has predicted that the Arctic could be ice-free in the summer as early as 2012, though others don't expect the ice to recede that quickly. The Pacific walrus’s winter sea-ice habitat is projected to decline 40% by mid-century if current greenhouse gas emissions continue, and any remaining sea ice in winter will be much thinner and will not last as long. On top of this, warming sea temperatures and sea-ice loss appear to be decreasing the abundance of the Pacific walrus’s bottom-dwelling prey. Habitat loss of this magnitude will commit Pacific walrus to population declines and an increased risk of extinction, according to the group.

At the same time the sea-ice habitat of the walrus is melting away, its most important foraging grounds are being auctioned off to oil companies to extract more fossil fuels that will further accelerate global warming and the melting of the Arctic. The Chukchi Lease Sale 193, held on February 6, 2008, resulted in 2.7 million acres of important Pacific walrus being bid on by oil companies, thereby opening the door for oil and gas development in a significant portion of the Pacific walrus’s summer range. Five other lease sales in the Pacific walrus’s habitat in the Chukchi, Beaufort and Bering Seas are planned by 2012. Increased oil and gas development and the proliferation of shipping routes in the increasingly ice-free Arctic pose threats to the Pacific walrus from the heightened risk of oil spills and rising levels of noise pollution and human disturbance.

“With rapid action to reduce greenhouse gas emissions, combined with a moratorium on new oil and gas development and shipping routes in the Arctic, we can still save the Pacific walrus, the polar bear, and the Arctic ecosystem,” added Wolf. “But the window of opportunity to act is closing rapidly.”

The Pacific walrus joins a growing list of species for which the Center for Biological Diversity has sought Endangered Species Act protection due to global warming. The Center filed petitions for the Kittlitz’s murrelet in 2001, the staghorn and elkhorn corals in the Caribbean in 2004, the polar bear in 2005, 12 of the world’s penguin species in 2006, and the American pika and the ribbon seal in 2007.

Oil and gas development, shipping, and greenhouse gas emissions affecting the Arctic would be subject to greater regulation under the Endangered Species Act if the walrus is listed. Listing of the Pacific walrus would not affect subsistence harvest of the species by Alaska Natives, which is exempted from the law’s prohibitions.

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