Climate Change will Spur More Frequent Wildfires, says Study
More Fires Will Lead to Major Shifts in Vegetation and Wildlife
The planet is getting hotter — hot enough to start fires. The Yellowstone National Park area is used to wildfires. Very severe fires break out in the region on an infrequent basis, killing trees and initiating secondary growth. But a study published in the Proceedings of the National Academy of Sciences predicts that by mid-century, these fires will greatly increase in their frequency.
Photo by Alex Indigo
"Large, severe fires are normal for this ecosystem. It has burned this way about every 100 to 300 years, for thousands of years," said study co-author Monica Turner, a professor of zoology at the University of Wisconsin, Madison. "But if the current relationship between climate and large fires holds true, a warming climate will drive more frequent large fires in the Greater Yellowstone Ecosystem in the future."
The researchers examined climate data from 1972 to 1999 and created statistical patterns by combining those data with figures on the size and frequency of Rocky Mountain fires in the same period. The models forecasted few years where no wildfires would break out by 2050, and fires like the historic one in 1988 that ravaged 1,200 square miles will become the norm by 2075. And after 2050, the average annual area burned will be nearly 400 square miles, making the fire pattern surprisingly similar to that of the Southwest, according to the study.
Annual fires could mean that lodgepole pines will have less time to recover in between blazes, making them susceptible to replacement by faster-growing varieties of shrubs and trees like aspen and Douglas fir. Wildlife could suffer, as well.
"More frequent fires will not be catastrophic to the area — Yellowstone will not be destroyed — but they will undoubtedly lead to major shifts in the vegetation," Turner said.
Yellowstone is not the only landscape to feel the heat of wildfires more often. More and more wildfires have been sighted in the Arctic tundra, which covers the northernmost fringes of North America and Eurasia, where the lower layers of soil are permanently frozen in a state called permafrost.
Vegetation there is limited to the few scrubby plants that can stand the cold. Scientists watch the tundra carefully because of its potential role in climate change. Intact, the upper layers of soil and plants absorb carbon dioxide from the atmosphere and insulate the permafrost below, keeping those layers cold. But damage, such as fires, to the tundra may actually accelerate global warming.
In 2007, lightning struck the remote North Slope of Alaska, starting the largest fire in the region since modern recording began in the 1950s. The fire burned for nearly three months, covering 400 square miles, until snowfall finally put it out in October. The charred remains were big enough to see from space. In a study published in Nature, scientists found that the 2007 blaze sent as much stored carbon up in smoke as the entire arctic tundra stores in a year, or three decades' worth of accumulated carbon for the region.
In addition to the released carbon dioxide, the fire significantly thinned the layer of soil that protects the permafrost. Also, the charred, dark surface on the burn site will absorb heat instead of reflecting it back into space as the snowy tundra usually does.
Essentially, more frequent wildfires are turning the Arctic tundra into a source of carbon dioxide instead of a sink.