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A study published in June by researchers from Boise State and other institutions found that wildfires have been climbing higher on mountain slopes in Western states.

The study published by the National Academy of Science found that between 1984 and 2017 fires had risen a median of more than 250 meters (820 feet).

Higher elevation forests such as those found at Colorado ski resorts (and, for that matter, at California’s Heavenly, at South Lake Tahoe) were once described as “asbestos” forests because they were moister and rarely burned, usually with intervals between fires of at least a century and often several centuries.

Climate change appears to be the major driver. The researchers in the study, “Warming enabled upslope advance in western US forest fires,” say the upslope advancement of higher-elevation fires of 7.6 meters per year compares to the elevational velocity of the vapor pressure deficit of 8.9 meters per year.

Geeked out? This may help: If the vapor pressure deficit is high, meaning the air is relatively dry, transpiration rates from plants—the flow of moisture from the plants to the air—is higher. Higher temperatures produce higher vapor deficit pressures, all things being equal. This is called aridity.

The researchers estimate that this reduced high-elevation flammability barrier caused by a warming climate has resulted in an additional 11% of Western forests becoming vulnerable to fires.

Another way of saying it is—as was demonstrated by the East Troublesome fire last year in Colorado, there’s no mountain too high. That fire leaped across the tundra of the Continental Divide.

This has significant implications of terrestrial carbon storage, snowpack and water quantity and quality, they say.

It also has implications for places like Vail, Crested Butte and Winter Park, which long thought they had no need to think about the threat of wildfires.

The Casper-Star Tribune talked with Mojtaba Sadegh, an associate professor in the civil engineering department at Boise State University and one of the authors. He said as temperatures warm, fires that used to be rare will become more frequent—and more severe. He said that thicker, steeper forests found at higher elevations are especially vulnerable to crown fires, as the flames race through the tree canopies.

He predicted much more study of higher-elevation fires, a relatively recent phenomenon of climate change.

Another study by Philip Higuera and other researchers at the universities of Montana and Wyoming found that the 2020 subalpine fire season in the Rocky Mountains was the region’s worst in 2,000 years.

See also: Colorado arrives at the dawn of megafires

And: Our new age of fire

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