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Global warming winners? North Slope brant thriving amid changes

Yereth Rosen
Rapid coastal erosion, aided by scarcity of sea ice, has exposed the ice-rich permafrost beneath the active layer just below the surface that the Teshekpuk Lake Special Area of the National Petroleum Reserve in Alaska.
Brandt Meixell / USGS
Geese, with digestive systems that are simpler than those of caribou, prefer the coastal plants because they have high protein content but less fiber than the uplands tundra.
Brandt Meixell / USGS
Inside the buried peat are remnants of old uplands vegetation that has been replaced by the salt-tolerant plants.
Brandt Meixell / USGS
A patch of land shows the difference in vegetation. On the left are the low-biomass, high-protein, salt-tolerant plants, preferred by geese, that are thriving as permafrost thaws and erosion eats away shorelines; on the right are the high-biomass, salt-intolerant tundra plants on which caribou forage.
Brandt Meixell / USGS
Soil core obtained from existing goose grazing lawn along the Smith River in the Teshekpuk Lake Special Area of the National Petroleum Reserve - Alaska. Buried peat layer broken open. Closer examination of the buried peat layer demonstrates that non-salt-tolerant vegetation from the past was buried in sediment which now supports high-quality goose forage.
Brandt Meixell / USGS
USGS Biologist Brandt Meixell and other scientists spend summers in the National Petroleum Reserve, where they are monitoring changes in plants and in goose behavior. They are doing some experiments to see what happens when tundra is cooled by shade or heated by greenhouse structures.
Laura Tennant / USGS
Black brant geese congregate at the Teshekpuk Lake Special Area to shed their worn-out flight feathers. The geese have altered their distribution on the North Slope to take advantage of new and favorable habitat along the Arctic Ocean shore.
Tyler Lewis / USGS

Diminished Arctic sea ice and thawing permafrost, phenomena that reinforce the climate change cycle and perpetuate the region’s warming trend, are not bad for all creatures of the north, a new study has found.

On Alaska’s North Slope, the changes have proved good for geese, according to a new study by scientists from the U.S. Geological Survey and the University of Alaska and published in the latest issue of Environmental Research Letters.

Brant -- a type of small, dark goose that winters in Baja Mexico and migrates each spring to Alaska -- are thriving on the changing North Slope coastline, the scientists found.

“Essentially, it looks like the brant population has grown both in numbers and in range,” said Paul Flint, a USGS wildlife biologist and study co-author.

Vegetation transformation

The brant gorge on salt-tolerant sedges called Carex subspathacea and other marshy plants that are replacing the upland sedges, grasses and other tundra plants that wither or die when exposed to salt. New coastal plants are sprouting as the coastal plain sags due to permafrost thaw and coastlines erode, a process accelerated by saltwater storm surges pushing inland with more power because there is less sea ice to restrain them. Those erosion- and thaw-caused changes in the Arctic coastal landscape have been documented by other USGS scientists who analyzed LiDAR data collected from 2006 to 2010.

On the ground, the vegetation transformation is noticeable, said Brandt Meixell, a USGS wildlife biologist and co-author of the brant study who spent three summers camping there doing field research.

The coastal “grazing lawns” that geese prefer “remind me of a wet, muddy putting green,” Meixell said in an email. “And the upland tundra is akin to the nastiest rough on the golf course ... taller, thicker vegetation and much more uneven ground.”

Beneath the surface, in the peat below the new salt-tolerant plants that have taken over the terrain, the scientists have found remains of uplands-type mosses and other plants that once dominated.

Along with the salt-intolerant plants, potential losers in this transformation are caribou, which prefer the uplands plants. But the reduction of caribou coastal forage is minimal compared to those animals’ wide territory and range, Flint said.

The study is part of several years of work to understand North Slope geese. The USGS began examining them in depth in 2006, when the Bureau of Land Management approved a new plan to guide future oil and gas leasing in the National Petroleum Reserve-Alaska. The BLM came to the USGS Alaska Science Center for guidance in minimizing oil development impacts to geese, Flint said. Those goose studies eventually led to the hypothesis that the transformation of North Slope vegetation has been good for the birds.

In a 2011 article published in the journal Polar Biology, Flint and other USGS scientists reported their findings that brant were -- contrary to an early theory -- not being crowded out of their feeding grounds by booming populations of white-fronted geese that were flocking to freshwater lakes.

Since the late 1970s, brant have moved to coastal areas from inland lakes during the molt period, when they're vulnerable. During the molt, birds shed old feathers worn out by the migration north and grow replacement features, typically losing weight in the process. About 70 percent of North Slope brant used to spend their molting period on inland lakes, but now 70 percent spend that period on the salty coastal areas, Flint said.

The shift is not because of white-fronted geese taking over lakes, the scientists found. There appeared to be plenty for all of the geese to eat, no matter where they chose to molt, the scientists found in that earlier study.

One possible byproduct of the new goose bounty: another food source for bears. Brown bears have been spotted feeding on goose eggs along the North Slope coastline, Flint said. Meanwhile, there has been some speculation about goose eggs becoming a dietary staple for threatened polar bears.

Polar bears in Canada’s Hudson Bay region have been filmed eating eggs from snow goose nests, and one 2010 study concluded that polar bears in that region could continue to eat the eggs without significantly harming the birds’ population because the egg incubation periods and ice-free periods when bears are on land are somewhat mismatched.

But Steve Amstrup, a polar bear biologist who was formerly with USGS and is now chief scientist at the nonprofit group Polar Bears International, cautions that goose eggs are unlikely to become major food sources for bears that depend on marine mammals.

Contact Yereth Rosen at yereth(at)alaskadispatch.com.