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Study: Wildfires could threaten Arctic caribou herd's winter habitat

Yereth RosenAlaska Dispatch News

Caribou in northern Alaska and Canada’s Yukon Territory will lose winter habitat if the region’s long-term pattern of increased wildfires continues, according to a study newly published in the journal PLOS ONE.

The Porcupine caribou herd, which straddles the Alaska-Yukon border, stands to lose 21 percent of the lichen-producing habitat they use in winter by the end of the century, said the study, conducted by scientists with the U.S. Geological Survey and the University of Alaska Fairbanks.

Habitat loss would be the result of wildfire-caused changes to the boreal forest that is used by the Porcupine herd as wintering grounds, said the study.

“That’s the big kicker about why we think they’re susceptible to the shift,” said Dave Gustine, a USGS research wildlife biologist who is the study’s lead author.

Up to 90 percent of the caribou’s winter diet is lichen, Gustine said. But the vegetation in the Porcupine herd’s wintering grounds -- the forested areas in northeastern Alaska and the northern Yukon -- is already undergoing a transformation triggered partly by wildfires, with different plants replacing the slow-growing lichen, he said. That region is known for its summer wildfires, he noted, and the intensity is expected to increase over the long term.

“Fires are bigger and they’re going to happen more frequently,” he said.

The Porcupine herd could potentially shift their wintering range, but that would not be easily accomplished, Gustine said.

“They could move east or west. The only problem with moving east or west is those areas are already occupied by other caribou herds,” he said.

The study is not good news for subsistence hunters in villages like Fort Yukon, Arctic Village and Old Crow, where residents rely heavily on caribou from the Porcupine herd.

Less susceptible to wildfire-caused vegetation changes, the study found, is the Central Arctic Caribou Herd, which winters in a more western region that straddles the tundra and the boreal forest. “So the lichen they’re getting is all above treeline,” where wildfires are less likely to damage lichen, Gustine said.

Though wildfires do occur occasionally on the tundra, they are far less frequent and far smaller than those in the boreal forests of northeastern Alaska and nearby Yukon areas, he said.

Loss of lichen-producing winter habitat used by the Central Arctic herd is expected to be about 11 percent by 2100, according to the study.

The study considered varying climate scenarios and a moderate scenario for future carbon emissions. Gustine said he is confident that all the scenarios used are conservative.

The study is part of the USGS Changing Arctic Ecosystems Program.

Effects of increased wildfires are not negative for all animals. A 2012 study found that while the Western Arctic Caribou Herd would lose habitat from increased wildfires, moose in the region would be winners.

The Western Arctic herd, the biggest caribou herd in North America, also uses winters in the boreal forest and eats lichen there.

That National Park Service-led study, published in the journal ESA Ecosphere, found that the herd’s caribou could lose nearly 30 percent of its core lichen-producing winter habitat to vegetation shifts caused by wildfires. But moose stand to gain 19 percent to 64 percent new browsing habitat if shrubs and trees replace the lichen, as expected, the study said.