Climate change will alter fire patterns, push caribou herds around

It’s not just the heat. Climate change will find (is finding) many creative ways to mess with wildlife and challenge conservationists. One such way is to change the patterns of fires that burn across animal habitats; in many areas, drought and heat have led to increases in fire frequency and severity. New research suggests that these changes have direct effects on caribou herds, an issue obviously for the caribou themselves as well as on human populations in the far north that rely on them.

This is a great example of how it’s not always the obvious effect that matters. Yes, more fire means fewer trees, but for caribou, it’s the lichen that grows on the trees and elsewhere on the tundra that matters most. Caribou subsist on these lichens, and they may be very slow to recover following severe fires. And those fires are coming more and more: half of the biggest fire years in Alaska (based on 60 years of recording), for example, have occurred since 1990, with two of the three biggest in the last decade.

Researchers from the U.S. Geological Survey and the University of Alaska at Fairbanks used climate modeling to assess how two large caribou herds in Alaska and the Yukon might fare in the future as the climate warms. The Central Arctic caribou herd, with about 70,000 individuals, spends most of its winters on the Arctic tundra, while the 169,000-strong Porcupine herd tends to winter in the boreal forest in the region.

They used two scenarios, one just “warm” and the other downright “hot”, and analyzed what would happen in terms of fire. Unsurprisingly, the “hot” scenario yielded a lot more charred acres of caribou habitat—64 percent more in the tundra, and 25 percent more in spruce forest regions. The amount of the study area that could be called suitable habitat for each herd didn’t change much under the warm scenario, but it changed dramatically under the hot version: an 11 percent decline in area through the end of the century in the forest, and a big 21 percent drop in tundra that could support the caribou. The amount of habitat that would be considered “highly flammable” would increase between two and four times in the hot scenario.

Okay, that’s just the “hot” scenario, you say: well, the authors say even that one is probably conservative given current greenhouse gas and warming trajectories. Still, it’s worth noting how complicated this sort of prediction really is, and the authors do so: “Projecting the influences of climate changes to wildlife populations is a necessary but daunting task fraught with numerous ecological climatic, and technical complexities, uncertainties, and assumptions.” Climate change is going to do things like this to animals and plants everywhere, and parsing out the specifics will be an ongoing challenge.

But even with all those caveats, the absolute best-case result of this sort of change in habitat is that the herds simply move. Maybe by heading north, or elsewhere, they may find more delicious lichen to eat every winter. But maybe not and the herds simply start to diminish in size, and even if they do it has spiraling effects, even on humans. “Culturally, barren-ground or migratory tundra caribou… constitute the most important terrestrial resource for subsistence hunters throughout the region, with many indigenous groups identifying themselves as ‘caribou people.'” It’s hard to stay caribou people if the caribou disappear. – Dave Levitan | July 8 2014

Source: Gustine DD, Brinkman TJ, Lindgren MA, et al (2014). Climate-driven effects of fire on winter habitat for caribou in the Alaskan-Yukon Arctic, PLoS One, 9 (7) e100588. DOI: 10.1371/journal.pone.0100588

Image:, Gouvi