Massive exodus from Tahoe Basin cauldron
2021 season: Drought, heat fueling bigger, faster blazes
An unrelenting series of wildfires is burning across California this summer, charring nearly 1.8 million acres so far and putting this fire season on track to surpass last year’s devastation, so far the worst on record.
Huge and fast-moving, these blazes — including the Caldor Fire which on Monday was surging toward Lake Tahoe — have covered more than 2,600 square miles, mostly in the Sierra Nevada. Noxious smoke and ash have coated the sky, threatening to hamper people’s immune defenses during the coronavirus pandemic.
The fire behavior has been supercharged, but there is some good news, too. Fewer people have lost homes compared to last year. And no one has been killed.
Even so, this year’s fires are growing to enormous sizes. Roads, highways and other fire breaks are failing to stop the flames. The nighttime hours, once a cooler, more humid refuge for firefighters to gain the upper hand, are instead producing aggressive, multimile burns.
A severe, two-year drought and an ever-warming climate have changed the rules.
Cal Fire Director Thom Porter said the state is in an “acute wildfire crisis.” Weeks
and months-long firefighting campaigns have become routine, and the veteran fire chief has been stunned by the sheer magnitude and ferocity of the fires.
“I keep hoping that things are going to be different this year, but I keep finding that it’s becoming normal to expect that each year will be worse than the last, or at least as bad,” Porter told The Chronicle.
Six of California’s seven largest fires have ignited within the past year. The Dixie Fire that started July 14 in Butte County and is burning through Plumas, Lassen, Shasta and Tehama counties has grown to more than 777,000 acres and is the second largest fire in state history. Only last year’s August Complex Fire surpasses it at more than 1 million acres.
A dozen major fires are responsible for most of the devastation so far this year — the 1.8 million acres is 2½ times the average number of acres burned during the same period over the past five years. It’s on pace with 2020, when a historic dry lightning storm sent massively destructive fires racing across the state. By this time last year, fire had destroyed just over 3,700 structures. So far, this year’s toll is about 2,500.
Porter describes many of this year’s blazes as “fuel-driven” fires, their growth fed by overgrown, drought-parched vegetation and terrain. Fires are expanding across massive tracts of unprecedentedly thirsty forest. And the “burn window” — the number of hours in a 24-hour cycle when fires are most active — has expanded deep into the night.
Cal Fire Assistant Chief Brian Newman, a fire behavior analyst working on the Dixie Fire, said he had to reprogram the state agency’s computer model when the blaze exceeded long-held calculations for predicting fire movement. Burning in timber, the fire was behaving as if it were in shrublands, where fires move faster.
But this year, living trees and fallen conifers that would normally retain some moisture from winter snow and rain are parched, with little defense against any spark.
“They’re drier than a 2-by-4 piece of lumber that you’d purchase at a hardware store which has been kiln dried and put out for sale,” Newman said.
The combination of snow-starved alpine timberlands and a stormy cold front whipped up the Dixie Fire in the Plumas National Forest and sent it roaring into Greenville.
Winds have a devilish affect on wildfire, and big ones can generate their own weather systems. The stunning pyrocumulus columns rising upward of 20,000 feet above the Dixie Fire pulled burning branches up into a windy soup then spit the embers out ahead of the main fire.
The Dixie Fire was a 274,000-acre inferno that had been burning for 22 days when it roared into Greenville on Aug. 4. Newman said conditions stacked up for an impossible firefight to save the Gold Rush town. A cold front bringing strong winds from the southwest hit a low-slung but steep and rugged region of the Sierra near the Lake Almanor basin. From the tree tops down to the soil, the area was incredibly dry after a disappointing winter and hot summer.
The fire would double in size over three days, throwing embers — spotting, it’s called — 6 miles ahead of the main fire. It shot forward 8 miles the first night, sending the blaze’s southern flank into Greenville. The town was virtually wiped out.
The Caldor Fire that ignited Aug. 14 in El Dorado County has burned more than 186,000 acres, threatening the Lake Tahoe basin. The fire exploded in size on day three when a cold front hit mountains. The fire raced 3½ miles overnight into the morning of Aug. 17, sending residents of Grizzly Flats fleeing — an unusual nighttime run when fires normally die down.
The sheer ferocity of the fires have had people wondering: Why this, why now?
“The common question I normally get is: Do I think this is related to climate change,” Newman said. “Regardless of the why or how we got to this place, is recognizing we are here. The climate is warmer. It is drier. The result of that is longer fire seasons. The drier the fuels, fires are more resistant to control.”
Recurrent drought is part of the West Coast climate, but winters have become drier in the past decade.
California’s snowpack is a key metric for understanding the climate’s impact on wildfires. In a typical year, the snowpack holds nearly onethird of the state’s freshwater. When it melts in spring, it fills reservoirs and creeks and soaks into the earth.
While the snowpack was about 75% below average statewide for the 2020-2021 rain year, it was the lack of runoff that shocked state hydrologists. Water coming off the mountains dropped to about 20% of the forecast, an estimate that already took into account the low amount of snow, according to the California Department of Water Resources.
“The water never showed up in the reservoirs,” said David Rizzardo, a top hydrologist with the water department. “It went two places as far as anyone can tell. It soaked into the ground because the ground was so thirsty. Or if you had heavy winds, it wiped it off the surface.”
And it wasn’t enough to replenish forests stressed by years of winters with below-average rain.
Rizzardo looks back over the past decade to understand the water situation: Drought years from 2012 to 2016 then 2020 to today. That 9year outlook was punctured by only three years with normal or flooding amounts of rain.
“If you want to fill that bucket, you want to (replace) what you’re missing and maintain what you’ve got,” Rizzardo said.
That’s harder to do after years of depletion.
Consider Plumas County, which has been hit repeatedly by wildfires this year: Annual rainfall plummeted from 76.5 inches in 2016-17, a wet season, to just 20 inches last winter.
Lack of snowpack and lack of rain — that drier atmosphere will draw more moisture from trees and other vegetation, a natural balancing act that means even slight rises in temperatures can have dramatic impacts on the ground, said Michael Wara, director of the climate and energy policy program at Stanford University.
“The plants have to pump water into the atmosphere to stay alive,” Wara said. “The soil is having water sucked out of it from this super large straw called the atmosphere.”
That means embers that might have landed on shaded, moist forest floor are instead finding dense, dried-out vegetation ready to burn. Flames that might have stayed close to the forest floor are climbing up crowded, brushy forests into the tree canopy. Up there, fire is impossible to control and flames can rise to 300 feet.
“We’ve seen these massive runs through timber,” Porter said. “Almost every ember that hits the ground is igniting a new fire.”
And it’s not just the lack of moisture in the ground and plants.
Californians are living with the consequences of decisions made more than a century ago to tamp down forests’ natural cycles of fire and regeneration. That has left the state with vast tracts of wildland strangled with vegetation.
In 1993, Susie Kocher was starting her forestry career in Greenville, working for the U.S. Forest Service in Plumas National Forest. Even then, the forest was too crowded with trees and brush, a problem she discussed with her mentors.
She was on a salvage team removing dead and dying trees after a bark beetle blight and inquired about cutting down some healthy trees to improve the forest’s ecology. But at that time the rules for removing living trees were more burdensome. Plus, it could draw the ire of some environmentalists, she said.
Thinner forests with less undergrowth keep fires closer to the ground and burn at lower intensity, giving the bigger, older trees a chance to survive.
“We knew it was important; we knew we should be doing it,” said Kocher, who now teaches private property owners how to use fire to clear their forests in the central Sierra through the University of California’s Agriculture and Natural Resource programs. “We didn’t and still don’t have a full mobilization to get the forests to a thinner state.”
Fires are a natural feature of West Coast forests and were historically used by Indigenous peoples to thin vegetation and manage the land. Those healthy fire cycles were interrupted on a massive scale with the displacement of native populations, said Sean Parks, a research ecologist who studies wildfires with the U.S. Forest Service’s Aldo Leopold Wilderness Research Institute in Missoula, Mont.
Fire suppression continued with federal policies, which govern 57% of California forestland, to extinguish every fire.
“Just because a fire is big doesn’t mean it’s bad,” Parks said. “There are other ways to measure the effects of a fire. There’s the human toll — houses lost, people’s lives lost and the social effects. Then there are the ecological effects: How many trees are killed by the fire?”
Parks studies wildfire severity. His research has found that the amount of severe, tree-killing fire across the western United States is accelerating each year, driven by climate conditions that are drying out the fuels.
The incredible buildup of vegetation over the decades has combined with a drier climate to create unstoppable fires that would be easier to tamp down with less extreme weather conditions, Parks said.
Decimated forests could transform into shrub- and grasslands without significant intervention. The effects could be enormous, he said, removing the forested umbrella that protects entire ecosystems and critical watersheds for Californians, destroying crucial habit for animals and beloved wildernesses that nurture the human spirit.
“Fire is inevitable and that’s something we need to recognize as we move forward,” Parks said. “If it’s inevitable, how do we want it to burn? That’s the choice.”
Porter has lamented that wildfires this year have already caused “generational destruction” within California’s timber basket, the northern Sierra Nevada region central to both commercial logging and the state’s plans for carbon sequestration.
The immediate impact on people has been less severe — fewer people forced to flee their homes and fewer homes lost compared to years past.
But those silver linings are no consolation for people who lost their homes and are also, in large part, due to chance. Most fires have ignited in remote areas, mostly federal forestlands. And it’s not yet September, when dry, inland wind storms bring some of California’s most dangerous fire weather.
“It feels like we’re coming back to the same situation over and over that is bigger than we are,” Porter said. “Mother Nature is in control, absolutely. And Mother Nature is having a hard time with these fires.”