The U.S. Fish and Wildlife Service announced that a petition presented by the Center for Biological Diversity provided substantial information that listing the walrus as threatened or endangered was warranted.
The determination was based in part on projected changes in sea ice associated with climate change. The Center for Biological Diversity and other groups successfully petitioned for protection of polar bears using the same argument.
Center spokeswoman Rebecca Noblin said Tuesday that unless immediate action is taken to reduce greenhouse gases, warming will claim walrus as a victim.
The U.S. Fish and Wildlife determination triggers a detailed status review, including a 60-day public comment period. The comment period closes Nov. 9.
"Climate change is the primary threat, but the offshore oil development in the Chukchi and Bering seas is also a problem," she said. Walruses could be forced into a land-based existence for which they are not adapted, she said.
The center petitioned for a walrus listing in February 2008 and sued in December when the agency missed its "90-day" initial finding deadline. The case was settled in May when the Fish and Wildlife Service agreed to make an initial determination by Sept. 10.
Walrus use sea ice to breed and forage. The animals dive from ice over the shallow outer continental shelf in search of clams and other benthic creatures. Females and their young traditionally use ice as a moving diving platform, riding it north like a conveyor belt as it recedes in spring and summer, first in the northern Bering Sea, then into the Chukchi Sea off Alaska's northwest coast.
Sea ice in the Chukchi Sea, shared with the Russian Far East, in 2007 and 2008 receded well beyond the outer continental shelf over water too deep for walruses to dive to reach clams. In fall 2007, herds congregated on Alaska and Siberia shores until ice re-formed.
Calves suffered high mortality on land due to trampling by those herds, Noblin said.
Conservation groups predict that if walrus are repeatedly forced to shore, they will over-hunt areas within short swimming distances and their population will crash.
Summer sea ice last year reached the second lowest level, 1.74 million square miles, since satellite monitoring began in 1979, according to the National Snow and Ice Data Center at the University of Colorado. The loss was exceeded only by the 1.65 million square miles in 2007.
The center reports ice extent declined more slowly in the first part of August this year due to a recent atmospheric circulation pattern, which transported ice toward the Siberian coast and discouraged export of ice out of the Arctic Ocean. The center said it was unlikely that 2009 will see a record low extent but the minimum summer ice will still be much lower than the 1979 to 2000 average.