Los Angeles Times

Fires reaching higher elevations

Climate warming is fueling extreme behavior, experts say

- By Hayley Smith

SOUTH LAKE TAHOE, Calif. — Just hours before the Caldor fire threatened to level the resort town of South Lake Tahoe, the massive blaze performed a staggering feat: burning from one side of the Sierra to the other.

It seared through crests and valleys, over foothills and ridges — and also at elevations of 8,000 feet or higher.

Ash and smoke rained down on the Tahoe basin and sent thousands fleeing from its soot-darkened shores as the fire skirted a towering granite ridge many believed would be a buffer from the flames. But the fire kept climbing higher, spewing wind-whipped embers that landed, in some cases, more than a mile away.

Experts said the fire’s extreme behavior is part of a worrisome trend driven by the state’s warming climate, in which rapid snowmelt and critical dryness are propelling wildfires to ever-higher elevations, scorching terrain that previously was too wet to burn and threatenin­g countless residents.

“What we’re seeing is that these fuels at high elevations that typically weren’t able to carry a fire, now are able to carry fire,” said John Abatzoglou, an associate professor of climatolog­y at UC Merced and coauthor of a recent study about wildfires at higher elevations. “That’s allowing these fires to effectivel­y reach new heights.”

The study, published in June in the Proceeding­s of the National Academy of Sciences, found that climate warming over the last few decades has exposed an additional 31,400 square miles of U.S. forests to fires at higher elevations.

It also found that between 1984 and 2017, fires in the Sierra Nevada advanced in elevation by more than 1,400 feet, surpassing some previously dependable moisture barriers.

Of the 15 ecological regions researcher­s studied, the Sierra Nevada was among three that saw the greatest upslope advances, along with the southern and middle Rockies.

“We do see in the Sierra Nevada that fires have increased in terms of their burned area over the past 40 years,” Abatzoglou said. “What’s novel here is that we’re documentin­g an additional shift in the elevationa­l bands where those fires are occurring.”

Before the year 2000, it was rare for a forest in the Sierra Nevada to burn above 8,200 feet, Abatzoglou said.

In the years since, there has been an eightfold increase in forested burned areas at that elevation. Both the Caldor fire and the Dixie fire — the state’s second-largest wildfire on record — passed that elevation threshold.

One of the most extreme examples, the 2020 Cameron

Peak fire in Colorado, blazed at above 12,000 feet elevation and jumped the Continenta­l Divide.

That extreme behavior may partially explain why the Caldor fire jumped the granite ridge overlookin­g the Tahoe basin, Abatzoglou said.

It also helps explain how the Caldor and Dixie fires became the first two to burn clear through the Sierra.

“Two times in our history, and they’re both happening

this month,” California Department of Forestry and Fire Protection Chief Thom Porter said. “We need to be really cognizant that there is fire activity happening in California that we have never seen before.”

Mark Schwartz, a professor emeritus at UC Davis, said the Dixie fire expanded rapidly as it crested and came down the east side of the Sierra. It also burned into Lassen Volcanic National Park, where it scaled some elevations of 8,500 feet or higher.

Some peaks and ridges near South Lake Tahoe are well over 8,000 feet and sparsely populated with fir trees. But dried vegetation is primed for ignition, enabling some fires to climb higher and send more embers aloft.

“This is dangerous,” Schwartz said, “because controllin­g wildfire has often relied on containmen­t at lower elevations, letting fires run out of fuels and fire weather at higher elevations.”

There are several factors that could be contributi­ng to this shift, but researcher­s said the primary cause is the warming trend that is exacerbati­ng the drought and drying out vegetation across the state. The vast majority of high-elevation fires in California are being ignited by lightning — which is more apt to start a fire when it strikes arid vegetation.

“There’s a good relationsh­ip between how warm and dry the vegetation is across the broader Sierra, and just how high those fires can carry up into these montane systems,” Abatzoglou said.

Higher elevations generally have snowpacks that last into June. When those melt, they bring an additional burst of water that keeps the vegetation wet. But with warmer temperatur­es and an ongoing drought, much of that moisture has disappeare­d.

On April 1, the date when California’s snowpack is typically at its maximum, the California Department of Water Resources recorded only 59% of its average depth. Rain in the Northern and Central Sierra was even lower, at 50% of average, which tied 2021 for the thirddries­t water year on record.

Mojtaba Sadegh, an assistant professor of civil engineerin­g at Boise State University and another of the fire study’s authors, said the region’s snowpack is entering into a dangerous cycle with higher-elevation fires.

“These high-elevation mountains are water towers for us,” Sadegh said. “Most of our water in the West is coming from that snowpack.”

When a fire burns high-elevation trees, it removes some of the canopy shading the snowpack and opens it to more melting sunlight, he said. That process also changes the reflectanc­e of the surface, exposing more dark ground and evaporatin­g more water.

It’s a cycle that can change the quantity and quality of water delivered to the state’s reservoirs, he said.

And while warming is the primary driver of the change, both the 2015 and 2021 studies noted that a century of fire suppressio­n in California has allowed an accumulati­on of vegetation to build up in forests, particular­ly in lower and middle elevations. When fire does arrive, it has more fuel to carry flames up and potentiall­y over the tops of ridges and mountains.

It’s something firefighte­rs have observed as they battle the state’s increasing­ly unpredicta­ble blazes, said Robert Foxworthy, a Cal Fire spokesman. Foxworthy said there’s been a “huge deficit” in the snowpack this year, along with massively desiccated vegetation.

The dried-out fuel conditions “are leading to these longer-duration fires, and burning at the higher elevations that we haven’t seen years in the past,” he said.

Although not every fire will soar to such altitudes, exceedingl­y high fires often are challengin­g to fight. Many high-elevation fires are in remote areas, and some small towns in those areas offer little infrastruc­ture and few roads for access or evacuation. Firefighte­rs are having to hike farther and higher, often with only the supplies they can carry.

And it’s not only firefighte­rs who are affected by the shift toward more higher-elevation fires. The blazes are also dangerous for the people who live below them; the fires can remove trees that help anchor against avalanches, researcher­s said.

 ?? Wally Skalij Los Angeles Times ?? FIREFIGHTE­RS work on the Caldor fire near Lake Tahoe on Sept. 2. Flames have reached above 8,000 feet, searing terrain that was once too wet to burn.
Wally Skalij Los Angeles Times FIREFIGHTE­RS work on the Caldor fire near Lake Tahoe on Sept. 2. Flames have reached above 8,000 feet, searing terrain that was once too wet to burn.
 ?? Luis Sinco Los Angeles Times ?? A SUNSET is obscured by burned trees and smoke from the Dixie fire last month near Janesville, Calif.
Luis Sinco Los Angeles Times A SUNSET is obscured by burned trees and smoke from the Dixie fire last month near Janesville, Calif.

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