Ice, Climate Change, and Wildlife Research in Alaska
DeGange, Anthony R., Endangered Species Bulletin
What do polar bears, Pacific walrus, spectacled eiders, and Kittlitz's murrelets have in common? In a word--ice! Although the effects of climate change can now be observed almost anywhere in the United States, nowhere are the effects more prominent than in Alaska, where unprecedented rates of sea ice loss, tidewater glacier recession, coastal erosion, permafrost degradation, and other landscape changes presage major changes to Alaska wildlife populations.
Climate change will play an increasingly significant role in future decisions related to the Endangered Species Act (ESA), and research is critical to understand how wildlife and their habitats will change as the climate continues to warm. These four ice-related species exemplify the diverse approaches to research undertaken by biologists in the U.S. Geological Survey's Alaska Science Center (ASC) to help unravel the mysteries associated with climate change and wildlife in Alaska.
The summer of 2007 set another record in sea ice loss in the Arctic since satellite measurements began in 1979. Two species are emblematic of Arctic sea ice: the polar bear (Ursus maritimus) and the Pacific walrus (Odobenus rosemarus). The Secretary of the Interior announced the listing of polar bears as threatened under the ESA on May 14, 2008. Polar bears depend on sea ice for much of their life history needs. They mate and den on sea ice, travel on sea ice, and feed almost exclusively on seals captured from the sea ice surface. Pacific walrus are currently the subject of a petition to list under the ESA.
The ASC's polar bear research team, under the direction of Steve Amstrup and George Durner, has been studying polar bears in Alaska for several decades. This extensive research record now enables comparisons of denning behavior, size and condition, and survival between periods when sea ice was abundant over the productive continental shelf and recent years, when it has been absent for increasingly longer periods of time. ASC biologists have documented a shift in the proportion of dens on sea ice to land in response to changing sea ice conditions, as well as declines in some measurements of body size and condition. Perhaps one of the most critical findings was the ability to link survival of polar bears to sea ice. In other words, survival of polar bears was higher in years when sea ice covered the continental shelf for longer periods of time, presumably because bears continued to have access to ice seals, their preferred prey. A similar relationship between sea ice and survival was also documented by ASC biologists, in collaboration with their Canadian colleagues, for polar bears in Western Hudson Bay, Canada.
In 2007, in response to requests from the Fish and Wildlife Service (FWS) and the Secretary of the Interior, the ASC assembled an international, interdisciplinary team of polar bear scientists, sea ice experts, and computer modelers to conduct analyses to help inform the listing decision on polar bears. In addition to understanding the current status of several polar bear subpopulations in Alaska and Canada, the team developed population and habitat models using sea ice forecasts from climate models to understand how the Southern Beaufort Sea polar bear population and polar bear sea ice habitat will change with future declines in sea ice.
The results of this study suggest a bleak outlook for polar bears. Polar bears were forecasted to decline throughout all of their range during this century, but the severity of the decline will depend upon the status of sea ice where they reside. In areas of seasonal sea ice, or where sea ice is receding far north of the continental shelf each summer and fall, extirpation was forecast as the most likely outcome for polar bears by mid-century. Polar bears were predicted to persist longer in areas of northern Canada and Greenland where sea is expected to be more stable. The ASC will continue its long-term studies of polar bears to evaluate and test the predictive models it recently developed. This is critical as sea ice continues to recede at unprecedented levels in the Arctic.
Pacific walrus are even more inaccessible and difficult to work on than polar bears. Developing and implementing a suitable method to estimate the population size of this species has been a dominant research focus for ASC scientists Chad Jay and Mark Udevitz and their colleagues, Doug Burn and Suzann Speckman of the FWS. With the survey data collection complete and analysis underway, the ASC has shifted its focus to better understanding the effects of climate change and diminishing sea ice on walrus. For example, it developed a satellite tag that could be remotely applied to walrus by using a crossbow from a small boat. This precluded the need for sedating walrus on sea ice--a dangerous proposition for walrus and researchers alike. With the recent additions of a saltwater switch and a pressure sensor to the tag, the ASC can now document where a particular walrus is, how much time it spends hauled out on land or sea ice, and where and for how long it is foraging. This will enable future comparisons of foraging efforts between walrus hauled out on land and those that remain on the sea ice.
Like polar bears, Pacific walrus spend a considerable portion of their annual cycle on sea ice. After breeding on sea ice in the Bering Sea in spring, many males migrate to terrestrial haul-outs in Bristol Bay, Alaska, and on the Chukotka Peninsula in Russia. Females and their dependent young, in contrast, stay on the ice as it recedes into the Chukchi Sea, where they use sea ice as a moving platform from which they dive to the sea-floor bottom to feed on such invertebrates as clams. Research suggests that loss of sea ice in summer and fall, particularly over the continental shelf of the Beaufort and Chukchi seas, is having a pronounced effect on this species.
In 2007, sea ice in the Chukchi Sea receded far over the deep water polar basin. Satellite tagging revealed that walrus stayed over the shallow water continental shelf where they had access to foraging areas for as long as possible by using small remnant ice flows for resting. Eventually, the ice disappeared and walruses used terrestrial haul-outs in Chukotka and Northwestern Alaska in unprecedented numbers. This behavioral change concerns wildlife managers and researchers for two reasons: walrus on land are at risk from disturbance, and reports from Chukotka suggest that many walruses were trampled during stampedes caused by human disturbances in fall 2007. Walrus also may increasingly compete with each other for food in the nearshore zone as they become concentrated in nearshore haulouts.
A discussion of climate change and wildlife in Alaska would be incomplete without mention of two unusual bird species also associated strongly with ice: the threatened spectacled eider (Somateria fischeri), which winters within the pack ice in shallow waters of the northern Bering Sea, and the Kittlitz's murrelet (Brachyramphus brevirostris), a small seabird that visits nearshore waters in summer and is associated with tidewater glaciers.
When research began on spectacled eiders, the wintering ground of this species was one of the great mysteries of ornithology in North America. In Alaska, that mystery was solved by ASC scientists Margaret Petersen and Dan Mulcahy, and Bill Larned of the FWS, with one of the first applications of implantable satellite transmitters. Since then, Petersen and Paul Flint of the ASC, and Chris Franson of USGS National Wildlife Health Center, used small portable x-ray devices to discover that spent lead shot deposited by waterfowl hunters on one of the eider's principal breeding grounds in Alaska was likely a critical factor affecting the survival of adult eiders.
ASC biologists are about to embark on a new satellite telemetry study of spectacled eiders in Alaska. The research will investigate how eiders are using nearshore areas of the Chukchi Sea that could be affected by oil and gas exploration and development. Equally important, the project also will allow investigators to reexamine how the eider's sea ice winter habitat in the northern Bering Sea may have changed since its discovery in the mid 1990s. This could be critical as commercial fisheries expand northwards towards critical habitat for wintering spectacled eiders.
The Kittlitz's murrelet, the only ESA listing candidate in Alaska, remains one of the most enigmatic of seabirds. Most of the world's population of this species, and all of North America's, breeds, molts, and winters in Alaska. They are locally abundant during the summer, nest solitarily, and probably disperse offshore over the continental shelf in winter. In southcentral and southeast Alaska, populations are usually associated with tidewater glaciers. Kittlitz's murrelets probably number fewer than 20,000 in Alaska. Steep declines in their population have coincided with the recession of Alaska's tidewater glaciers in recent decades, but the exact nature of the relationship between birds and glaciers is unknown. This question is under investigation in the Kenai Fjords of southcentral Alaska by ASC biologists John Piatt and Yumi Arimitsu. Piatt is also collaborating with Vernon Byrd, Bill Pyle, and other FWS biologists to investigate the breeding biology of murrelets at Attu Island and Kodiak Island in southwestern Alaska.
A warming climate is causing rapid changes to Arctic ecosystems. Some plant and animal species will respond favorably to these changes, others will not. This poses unprecedented challenges to fish and wildlife managers. As these research vignettes indicate, wildlife research has an important role to play in wildlife conservation in a changing Arctic, and they highlight the continuing need for a strong partnership between the FWS and the USGS.
Anthony DeGange (tdgange@usgs. gov, 907-786--7406) is the Chief of the Biology Office at the Alaska Science Center in Anchorage, Alaska.…