The federal Marine Mammal Commission has recommended that Pacific walrus be listed as threatened or endangered, citing threats to the marine mammals from the loss of sea ice they rely on for foraging and giving birth.
The recommendation comes as the U.S. Fish and Wildlife Service faces a court-ordered deadline at the end of the month to decide whether to recommend walrus for the endangered-species list.
The three-member Marine Mammal Commission oversees marine mammal conservation policies carried out by federal regulatory agencies.
"Without question, the warming of the Arctic is destroying, modifying, and curtailing walrus habitat and will continue to do so in the foreseeable future," the commission said in a letter to Rowand Gould, acting USFWS director.
Scientists at the National Snow and Ice Data Center have tracked a steady decline in sea ice in recent decades and say summer sea ice could disappear by 2030.
Commissioner Vera Alexander, president of the Arctic Research Consortium of the United States, said all three members endorsed the recommendation, as did their scientific advisers.
"Obviously, nobody knows what's going to happen with the sea ice changing so dramatically but there's certainly a lot of concern," she said. "In a sense, that letter is precautionary."
Alaska's walrus population spends virtually the entire winter in the Bering Sea on the edge of sea ice that forms every year. In spring, as temperatures warm, ice melts and the edge of the sea ice moves north.
Older males spend the summer in the Bering Sea, foraging from islands or remote coastal shores. Females and pups, however, ride the ice edge through the Bering Strait and into the Chukchi and Beaufort seas, diving to the shallow continental shelf in search of clams as pups rest above them, safe from predators.
In recent years, however, sea ice in summer has receded well beyond the continental shelf, over water too deep for walrus to dive to reach clams.
Walrus in three of the last four years congregated by the thousands on Alaska's northwest shore. Larger numbers took refuge on the Russian side of the Chukchi Sea.
Without their ice platform, walrus cannot reach the best foraging areas, Alexander said.
"The nearshore assemblage of organisms is not as useful for them," she said.
In February 2008, the Center for Biological Diversity petitioned to list walrus as threatened or endangered, citing threats to sea ice from global warming. The group sued when the Fish and Wildlife Service missed a 90-day deadline to determine whether the petition had merit.
The Marine Mammal Commission noted that modeling conducted for the Intergovernmental Panel on Climate Change showed ice continuing to decline for the foreseeable future unless human societies take "meaningful action" to address factors disrupting climate.
Even if action is taken soon, the commission said, their effects would not be clearly evident until the latter half of the century because of the lagged effect of greenhouse gases already emitted.
Former Interior Secretary Dirk Kempthorne in 2008 put polar bears on the threatened species ice because of sea ice loss.
The National Oceanic and Atmospheric Administration last month announced it will seek to list the main prey of polar bears, ringed seals, as threatened because of ice loss and reduced snow cover due to warming. NOAA also proposed listing two populations of bearded seals, which give birth on drifting pack ice.
Fish and Wildlife Service spokesman Bruce Woods said a decision on walrus is expected near the Jan. 31 deadline.