By Nick Sundt
From the WWF Climate Blog
Walruses haul-out along Alaska’s shoreline of the Chukchi Sea. (c) USGS
On 30 August we first noted evidence that walruses were being forced ashore as sea-ice disappeared from the Chukchi (see Walruses Again Being Forced Ashore as Arctic Sea Ice Retreats). Arctic sea ice continued to decline and by Friday 3 September had dropped to the third lowest extent on record (see Arctic Sea Ice Extent Now Third Lowest on Record — and Still Dropping), as the USGS reported that thousands of walruses were hauling out on the Alaska shore (see USGS Alaska Science Center Weekly Highlights for 9-2-2010 and our 7 September posting, USGS Confirms Thousands of Walruses Hauling-Out on Alaska’s Northwest Coast as Sea Ice Rapidly Retreats).
Last year under similar sea ice conditions, there were comparable haul-outs on the Russian shoreline of the Chukchi; and smaller haul-outs on the Alaskan side.
According to Alaska Dispatch:
“USGS scientists traveled to Point Lay earlier this month to tag some of the walruses in an effort to track and study their movement. They’re particularly interested in how much more swimming the hauled out walruses, most of which are females, will have to do to find food and how that extra effort will affect the animals’ health. They’re also worried about how young walruses — which rely on a mother’s care for two years and which nurse for the first six to seven months of life — will fare.”
Conditions Imperil Young Walruses
A walrus pup alone in the Arctic Ocean in 2006, one of nine calves seen swimming far from shore at the time and presumed to have died (c) Carin Ashjian, Woods Hole Oceanographic Institution
Before the young walruses can haul-out onshore, they must survive an extended period offshore without sea-ice to rest on and must successfully make the long voyage with their mothers to the coast. As sea ice has receded over the last decade, young walruses are increasingly separated from their mothers, drifting in the open-sea. For example, according to Walrus Calves Stranded by Melting Sea Ice, a posting (13 April 2006) from the Woods Hole Oceanographic Institution:
“Nine lone walrus calves were reported swimming in deep waters far from shore by researchers aboard the U.S. Coast Guard icebreaker Healy during a cruise in the Canada Basin in the summer of 2004. Unable to forage for themselves, the calves were likely to drown or starve, the scientists said.
Lone walrus calves far from shore have not been described before, the researchers report in the April issue of Aquatic Mammals. The sightings suggest that increased polar warming may lead to decreases in the walrus population.
`We were on a station for 24 hours, and the calves would be swimming around us crying. We couldn’t rescue them,‘ said Carin Ashjian, a biologist at Woods Hole Oceanographic Institution and a member of the research team….`If walruses and other ice-associated marine mammals cannot adapt to caring for their young in shallow waters without sea-ice available as a resting platform between dives to the sea floor, a significant population decline of this species could occur,’ the research team wrote.”
Where the young walruses survive the ordeal offshore, they find new perils along the coastline. When walruses congregate in large numbers onshore, they may stampede into the water if frightened. The smaller females and young may be trampled to death. This has occurred along the Russian shoreline in recent years; and was documented last year along the Alaskan shore.
On 14 September 2009, scientists encountered 131 walrus carcasses near Icy Cape, Alaska. A USGS report (Enumeration of Pacific Walrus Carcasses on Beaches of the Chukchi Sea in Alaska Following a Mortality Event, September 2009) said:
“All appeared to be young animals …. The events that led to the death of these animals are unknown, but appear to be related to the loss of sea ice over the Chukchi Sea continental shelf. In years prior to this event, other investigators have linked walrus deaths at other Chukchi Sea coastal haulouts to trampling, exhaustion from prolonged exposure to open sea conditions, and separation of calves from their mothers.”
“Were it not for the dramatic decline in the sea ice, the young walruses at Icy Cape most likely would be alive on the ice and not dead on a beach,” said WWF biologist Geoff York last September.
A yearling calf (center) with its mother hauled-out at Point Lay, Alaska. The smaller younger walruses can be trampled to death when much larger adults are frightened into stampeding into the water (c) USGS
Dead calf walrus in front of the village of Wainwright 42 miles north of Icy Cape, Alaska, September 2009 (c) USGS
Federal Report Identifies “Clear Trend of Worsening Conditions for the Pacific Walrus,” over the Course of the 21st Century
On Friday (10 September 2010), the USGS released Projected status of the Pacific walrus (Odobenus rosmarus divergens) in the 21st century, summarizing its model-based assessment of the prospects of walruses during the rest of this century. The results show a “clear trend of worsening conditions for the Pacific walrus,” with the decline of sea ice — especially in summer and fall — identified as one of the dominant factors. The researchers linked the decreased sea ice habitat to “decreased body condition from poorer ice availability and increased total mortality from increased crowding and disturbance mortalities on the haul-outs.”
The study finds that the summed probabilities of the the walrus population being “vulnerable,” “rare” or “extirpated” (i.e. “absent through all, or nearly all, of the Chukchi and Bering Sea region”) could increase from the current 5% in 2004 to 40% by 2095.
The study says that “projections indicate that ice-free conditions over the entire [Chukchi] shelf will occur during August, September, and October (during summer/fall) by the end of the century.” That is consistent with a report released last month (August 2010) by USGS, Arctic sea ice decline: Projected changes in timing and extent of sea ice in the Bering and Chukchi Seas. However, the researchers in the August study note: “The present condition of Arctic sea ice and its steep rate of decline warrant serious consideration to the possibility that the CMIP3 GCM [model] projections collectively portray 21st century sea ice losses on a conservative time frame.”
Similarly, the study released on Friday acknowledge that “summer Arctic sea ice extent could decline more rapidly than forecasted…” Should that in fact occur, they say, “changes in the status of the walrus population could occur more rapidly…”
In a press release issued yesterday (Pacific Walrus Faces Dire Future: Federal Report Predicts Extinction Risk Due to Global Warming), the Center for Biological Diversity responded to the findings:
“Today’s report, although based on optimistic and ultimately unrealistic assumptions about sea-ice loss, reaffirms what is all too obvious: Unless we dramatically reduce our greenhouse emissions, the walrus is on a trajectory toward extinction,” said Rebecca Noblin, the Center’s Alaska director. “The walrus clearly meets the criteria for protection under the Endangered Species Act.”
The USGS used climate models that underestimate emissions, warming and rates of Arctic sea-ice loss. The report also dismissed as negligible the impacts from reduced food supply for the walrus. Sea-ice loss in the Bering Sea is already leading to declines in the walrus’s bottom-dwelling prey; ocean acidification is making Arctic waters increasingly corrosive and potentially lethal to the clams and mussels it eats. Still, the USGS determined that these threats have negligible influences on the walrus’s future. The study would have found a significantly worse outlook for walruses if it had used more realistic assessments of these threats.
While global warming and ocean acidification are the greatest threats to the Pacific walrus, the species is also threatened by the Interior Department’s plans to allow offshore oil drilling in its Chukchi Sea habitat.
“The Endangered Species Act is our nation’s strongest law for wildlife protection and, properly applied, can help the walrus survive the stress of a melting Arctic,” said Noblin. “But unless we take immediate action to reduce greenhouse pollution, the grim reaper of global warming will ultimately claim the Pacific walrus as a victim.”
The CBD in February 2008 petitioned the U.S. Fish and Wildlife Service to protect the Pacific walrus under the Endangered Species Act. The agency must decide whether the walrus will be protected under the law by January 31, 2011.
By Nick Sundt