Changing Arctic Ecosystems: Sea-Ice Decline, Permafrost Thaw and Benefits for Geese

A warming coast

Through its Changing Arctic Ecosystems initiative, the U.S. Geological Survey studies how Arctic Alaska's ecosystems are responding to a warming climate, to inform resource management. A focus has been the Arctic Coastal Plain of northern Alaska, which has warmed over the past 30 years. Sea ice has shrunk and permafrost has thawed. With less sea ice, waves have grown stronger, eroding the coast and flooding coastal habitats with salt water.

Salt-tolerant plants are now thriving in those places — and that appears to be good news for geese, the opposite of what declining sea ice means for ice-dependent animals such as polar bears and walruses.

The Pacific Black Brant's year

Many birds that summer on the coastal plain migrate great distances, from wintering grounds as far away as South America and Asia. Pacific Black Brant arrive in Alaska by the thousands each summer to breed and to molt — a late-summer event in which they replace worn flight feathers and cannot fly for 3–4 weeks — before flying south to winter in British Columbia, California and Mexico. While molting they need high-quality food and open water where they can escape predators.

Pacific Black Brant in flight. Photograph by Kelly Warren, U.S. Fish and Wildlife Service.

Brant move to the coast

Since the 1970s, U.S. Fish and Wildlife Service data have shown molting brant near Teshekpuk Lake, a large lake southeast of Barrow, changing where they go. The USGS found that brant — younger geese especially — are using new molting areas on the coast instead of the large inland lakes they traditionally used. Later Fish and Wildlife Service surveys of the new coastal areas recorded a 50 percent increase in molting brant along the coastal plain. The reason is more high-quality food along the coast, brought about by less sea ice.

Molting Black Brant have shifted from inland lakes to coastal areas where saltwater flooding has created new foraging habitat. Data from the U.S. Fish and Wildlife Service Migratory Bird Management.

How the habitat is changing

Time-series imagery and soil analysis show permafrost thawing and upland tundra sinking. With less sea ice, storm surges pushed salt water farther inland and buried plants that cannot tolerate salt. The new coastal mudflats are productive ground for the salt-tolerant plants geese prefer, which is what drew the molting geese there.

Thawing permafrost, subsidence, saltwater flooding and new sediment turn upland into mudflats, where Black Brant find new, high-quality food. USGS.

Further loss of sea ice and permafrost may keep reshaping the coast, creating more salt marsh and more high-quality goose food. Other geese are responding to similar warming-driven changes: White-fronted Geese on the coastal plain have increased since 1980, and Lesser Snow Geese have increased dramatically in the past few years.

Coastal erosion on the North Slope of Alaska. Photograph by John Pearce, U.S. Geological Survey.

What comes next

This research is helping land managers such as the Bureau of Land Management decide which areas may need special care when planning for possible industrial development on the North Slope. The key finding: as habitats change, wildlife populations are changing in both numbers and distribution. The USGS is building forecasts of future goose habitat so plans for development can account for where wildlife and habitat will be. Future work will look at how much more habitat may convert on the coastal plain, and whether the changes driven by sea ice and permafrost are adding high-quality coastal forage overall, or whether habitat is being lost to erosion — or both.

Sources

• Flint, P., Whalen, M., and Pearce, J., 2014, Changing Arctic ecosystems—Sea ice decline, permafrost thaw, and benefits for geese: U.S. Geological Survey Fact Sheet 2014–3088. https://pubs.usgs.gov/publication/fs20143088 — the figures and U.S. Fish and Wildlife Service and USGS photographs come from its PDF; an orthoimage series from a journal paper and a University of Alaska photograph are left out.
• Research papers cited by the fact sheet include Flint and others, Polar Biology (2008) and Journal of Field Ornithology (2014); Lewis and others, Waterbirds (2011) and Polar Biology (2011); and Tape and others, Environmental Research Letters (2013).