USGS Arctic Ecosystem Assessments: Caribou, Birds, Walrus, Polar Bears and Permafrost

The U.S. Geological Survey assesses natural hazards and resources, and how ecosystems respond to environmental change, human activity and land use. Arctic Alaska matters for cultural and economic sustainability and is home to many species of conservation and management interest to the Department of the Interior. Arctic residents, management agencies and industry use what the USGS and its partners learn there. This 2021 fact sheet sums up recent assessments.

Caribou

Caribou in northern Alaska. U.S. Geological Survey photograph.

Energy development has long been part of the Central Arctic Herd's summer range, yet female caribou (Rangifer tarandus) still avoided oil infrastructure in summer. The avoidance faded over the season:

This adds to growing evidence that Arctic caribou get used to industrial development weakly or not at all — and to the case for keeping infrastructure's footprint small in important seasonal habitat.

Migratory birds

Oil development on Alaska's Arctic Coastal Plain may harm Arctic-nesting birds.

• Geese. Human foot traffic cut the survival of white-fronted goose (Anser albifrons) nests by 7–35 percent. Construction noise at a distance, vehicle traffic and low-flying aircraft did not change nesting geese's behaviour — so avoiding direct disturbance in breeding areas is what counts.
• Loons. Buffer zones around nests of disturbance-sensitive yellow-billed loons (Gavia adamsii) in development areas matched loon movements during nesting well — for yellow-billed, red-throated (G. stellata) and Pacific loons (G. pacifica) alike.
• Waterbird trends. Using 25 years (1992–2016) of U.S. Fish and Wildlife Service aerial surveys, the USGS estimated the distribution, abundance and trend of 20 breeding waterbird species. Important areas included the coast near Teshekpuk Lake, the Colville River Delta and Admiralty Bay, and the National Petroleum Reserve in Alaska (NPR-A) was important for every species examined. Over the period, 13 species increased, 6 were stable and 1 declined — the red-throated loon. Nearly all species shifted where they bred, suggesting they are responding to changing local habitat, possibly driven by warming.

Snow goose goslings in northern Alaska. U.S. Geological Survey photograph.

Pacific walrus

To limit disturbance of Pacific walruses (Odobenus rosmarus divergens), managers need to know how many there are and where they haul out. In autumn, when sea ice retreats from parts of the Chukchi Sea, large numbers of adult females and young come ashore at coastal haulouts, where young walruses can be trampled to death if the herd is disturbed.

• The USGS compiled records of Pacific walrus haulouts going back to 1852 into a public, georeferenced database used for maps and other tools.
• It assessed population dynamics from 1974 to 2015 — size, age structure, reproduction and harvest — and found a decline over several decades that began to ease in the 1990s and may have ended by 2015.

A Pacific walrus on an ice floe. U.S. Geological Survey photograph.

Polar bears

The biggest influence on the polar bear's (Ursus maritimus) future is sea ice, which bears use to feed, mate and den. Less sea ice has reduced Alaska's southern Beaufort Sea subpopulation and pushed more mothers to den on land.

• In the Alaska part of the subpopulation, numbers fell from about 1,300 bears in 2003 to 525 in 2006, then held roughly steady to 2015.
• 66 of 123 yearly dens across the whole subpopulation — more than half — were on land in northern Alaska. Most were between the Colville and Canning Rivers, which include the Prudhoe Bay–Kuparuk industrial area, followed by the 1002 Area of the Arctic National Wildlife Refuge and the NPR-A.

A polar bear in the southern Beaufort Sea. U.S. Geological Survey photograph.

Biosurveillance

Harmful algal blooms. Warmer seawater is linked to harmful algal blooms, whose toxins can sicken or kill wildlife. Since 2015, widespread seabird die-offs have occurred every year in many Alaskan ecoregions alongside marine heat waves. The USGS found the algal neurotoxin saxitoxin in some local die-offs, including in the Arctic, though starvation was the main cause of death. It has found saxitoxin in dead and healthy seabirds, forage fish and marine invertebrates throughout Alaska's coastal waters. With those findings and its experiments, the USGS concludes that algal blooms should be part of future health assessments of Arctic seabirds and marine mammals.

Avian influenza. Alaska is a globally important crossroads for bird-borne influenza A viruses: its vast wetlands host birds that migrate between four continents. USGS sampling of wild birds there has repeatedly found viruses moving between East Asia and North America, making Alaska a key entry point for foreign bird pathogens. The USGS has summarised decades of this work to guide continental biosurveillance, and also watches for toxoplasma, tularemia and brucellosis.

Permafrost

The USGS has summarised how far permafrost extends in Alaska, its role, and the risks its thaw poses to living and water resources.

• Erosion. Warmer permafrost and longer ice-free seasons over recent decades have sped up coastal erosion — in parts of northern Alaska, such as the NPR-A, to as much as 22 meters (about 72 feet) a year. The changing coast is altering wetlands and the distribution and abundance of wildlife.
• Mercury. Northern Hemisphere permafrost holds an estimated twice as much mercury as the atmosphere, oceans and non-permafrost soils combined; its release as permafrost thaws is a substantial risk to ecosystem health.

Coming next

The USGS Changing Arctic Ecosystems web page describes assessments in progress:

• how spring timing affects where the Porcupine caribou herd goes, now and in future;
• how moulting black brant geese (Branta bernicla) respond to helicopter disturbance in the NPR-A;
• trends in Pacific walrus and southern Beaufort Sea polar bears from 2015 on;
• how shipping affects walrus behaviour in the Chukchi Sea;
• autumn numbers of walrus in the northeastern Chukchi Sea.

Sources

• Pearce, J.M., and Van Hemert, C.R., 2021, U.S. Geological Survey Arctic ecosystem assessments: U.S. Geological Survey Fact Sheet 2021-3016. https://pubs.usgs.gov/publication/fs20213016
• The introduction and the photographs come from the fact sheet's PDF, which the web version lacks.
• Rewritten in hubnx's own words.