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California wildfires are climbing higher up mountains, putting more forest at risk of flames

California’s wildfires are not only getting bigger, they’re moving higher, reaching once unthinkable heights.

The still-burning Dixie Fire was the first to push over the towering Sierra Nevada, igniting on the western side of the mountain range and catapulting to the valley floor on the east. The blaze, in the state’s remote north, also climbed into Lassen Volcanic National Park, where it was recently burning near 8,500 feet.

Other large fires have gotten even higher. Last year’s devastating Creek Fire and Sequoia Complex fires in the southern Sierra approached the dizzying elevation of 10,000 feet, a point at which trees and other burnable vegetation become exceedingly sparse.

These high-elevation burns, which are among the surge of big fires in California over the past few years, are the direct result of the warming climate, scientists say. And they’re exacerbating the wildfire crisis by charring tracts of land that were long considered too cool to burn. They’re also harder for firefighters to get to.

One study published this spring suggests that 11% more forest across the West, or 31,500 square miles, has become susceptible to burning over the past 3½ decades because of the expanded reach of flames. Nearly 2,400 square miles of this newly at-risk land are in the Sierra.

“We’re just opening up more opportunities for fires,” said John Abatzoglou, an associate professor of climatology at UC Merced and one of the authors of the recent paper. “We expect, moving forward, that high-elevation forests will just burn more regularly.”

Abatzoglou’s research, published in the journal Proceedings of the National Academy of Sciences, found that California’s wildfires are migrating upward even faster than those in most Western states.

During his study period of 1984 to 2017, the upper reach of fires in the Sierra rose more than 1,400 feet, compared with 827 feet across all mountain ranges in the West. The upper reach refers to the point at which only 10% of fires burn higher.

Several mechanisms are behind the climate-driven climb. Increasing temperatures are drying out mountain forests as well as reducing the amount of snow that keeps them moist. Some places are seeing less precipitation. Also, many of these forests have become thicker with vegetation because of the heat, all of which is making higher elevations ripe for burning.

In addition, some spots are experiencing increases in lightning, meaning more ignitions, too.

“It’s the future that we face,” said Mark Schwartz, a plant ecologist and professor emeritus at UC Davis who also has researched the upward creep of wildfire. “There’s just more continuous fuels, which are allowing more fires to get to that high-elevation zone.”

The Dixie Fire, he said, is a perfect example. The fire started July 13 in the Feather River Canyon in Butte County at about 1,500 feet and has since climbed to above 8,000 feet. It’s become the second-largest blaze in California history.

While the Dixie Fire’s elevation may not be as high as some fires to the south, the cooler weather and moister conditions in the north make the ascent just as impressive, perhaps more so.

The upward migration of wildfire may play a role in fundamentally changing the landscape at higher elevations, too, and make these areas even more prone to burning in the future.

California wildfires are climbing higher up mountains, putting more forest at risk of flames

The trees that characterize the upper edge of Sierra forest at about 8,000 to 9,500 feet, such as white pine and mountain hemlock, are less adapted to fire and don’t do as well with rising temperatures. When and if they burn, they could be replaced by other pines and fir better suited to these newer conditions, trees that generally burn a lot more frequently.

“An ecological model of vegetation change would suggest you get upward movement of red fir and the capacity to have more fuels” for fire, Schwartz said.

Managing fire at higher elevations, including putting them out, comes with its own set of challenges. Long treks for fire crews and more restrictions on aircraft are just a couple.

“The further up you go, and in general, the more remote you are, the harder it is to supply firefighters to the line and support them logistically,” said Nic Elmquist, a fire behavior analyst for the U.S. Forest Service, which operates the nation’s largest wildland firefighting force. “When you get a year like this year, in all honestly, teams are already stretched to the limit.”

The Sierra’s high country has long been considered a place where firefighters haven’t had to worry much about suppressing wildfires. The fires often burned themselves out amid the cooler, moister conditions and lesser amounts of vegetation to feed flames. Fire crews sometimes steer blazes to high elevations for this reason.

But as the higher areas become more at risk of burning, fire managers have had to reassess their strategy.

A firefighter watches a spot fire from the Dixie Fire near Susanville (Lassen County). The blaze was the first to push over the towering Sierra.

A firefighter watches a spot fire from the Dixie Fire near Susanville (Lassen County). The blaze was the first to push over the towering Sierra.

Patrick T. Fallon / AFP / Getty Images

“All bets are off,” said Ken Pimlott, a professional forester and former director of Cal Fire, the state’s firefighting agency. “High-elevation fires change the dynamic. You can’t count on the Sierra crest as a natural barrier anymore.”

Pimlott was among many who were critical of the Forest Service this summer for not being more aggressive about putting out the Tamarack Fire, south of Lake Tahoe. The agency sent firefighters to the blaze six days after it started on July 4, during which time it went from a small fire on a remote mountain ridge at about 7,500 feet to a giant inferno burning to 9,000 feet and threatening the Alpine County community of Markleeville.

Forest Service officials said with limited staffing, they had no choice but to prioritize more threatening burns. The Tamarack Fire, which ignited with a lightning strike in a spot with little vegetation, was one that might have burned itself out in the high country, if not for the uptick in wind and heat that ensued.

“It’s hard in California to find locations anymore where a fire is not going to be influenced by these conditions,” Pimlott said. “Maybe historically that would have been the approach, but you can’t do that now.”



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