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Calif.'s largest fire tops 64,000 acres, still threatening homes, air quality, giant sequoias

At just 20% containment, the Mosquito Fire has destroyed 70 homes and structures and is threatening 9,000 more


A firefighter hoses down hotspots as the Mosquito Fire burns in Placer County, Calif., on Tuesday.

Photo/Noah Berger

Grace Toohey
Los Angeles Times

LOS ANGELES — The Mosquito Fire in the Sierra Nevada foothills is California’s largest blaze this year, and it continued to grow Thursday, threatening thousands of homes and the region’s air quality, as well as a historic grove of giant sequoias.

Fire officials are hopeful some moisture in the forecast this weekend could bring some relief, but remain wary that the predicted rain — likely no more than an inch — could make a significant difference in the firefight in Placer and El Dorado counties.

“The storm coming in ... that’s going to bring some wind with it,” said Scott McLean, a public information officer for the California Department of Forestry and Fire Protection. “We’ll see if we get any rain over the fire.”

The wildfire has grown to 64,159 acres as of Thursday morning and is still just 20% contained, according to CAL FIRE. More than 9,000 homes and structures remain threatened by the flames, and 70 have already been destroyed. McLean said about 11,000 people have been ordered to evacuate since the fire began more than a week ago, with those orders still in place.

“It will continue to grow to a certain extent,” McLean said. “This fire’s been primarily topography- and fuel-driven. ... The terrain is just horrendous trying to get resources in there.”

That “historically dry” fuel coupled with particular atmospheric conditions has sparked massive plumes off the blaze, shooting smoke and debris tens of thousands of feet into the air — blanketing much of the region in a dangerous haze that hasn’t let up.

The Reno area remains at “very unhealthy” air quality levels, up to 100 miles from the Mosquito fire, according to the Washoe County Air Quality Management Division. Many communities across California’s central and northern Sierra foothills, including Grass Valley, have been affected.

The Mosquito Fire’s massive plumes of smoke spreading far beyond its boundary is only the latest example of how wildfires in recent years, especially in California’s Sierra Nevadas, are forming higher-than-ever plumes, which spread dangerous air quality across greater distances, according to a recent study from the University of Utah.

“Our findings suggest that wildfire activity in the Western U.S. presents a growing risk in terms of long-range smoke transport and air quality degradation,” the team from the university’s Department of Atmospheric Sciences found.

“These kind of wildfire-generated air quality issues are going to be a problem into the future, and now we have reason to believe that that air quality degradation might spread further spatially,” said Kai Wilmot, a postdoctoral researcher who worked on the study. He said that when smoke enters higher portions of the atmosphere — as prompted by higher plumes — smoke can move more efficiently, and also be caught in different wind speeds and directions, making it travel not just farther, but also in numerous directions.

The Mosquito fire is also threatening one of the smallest groves of giant sequoia in the state, located near the southern edge of the Tahoe National Forest.

“In the past two years, we’ve lost nearly 20% of all giant sequoias on earth in high severity fires, so we’re going to great lengths to make sure that this grove is not part of that statistic,” Garrett Dickman, a forest ecologist from Yosemite National Park, told OnScene.TV.

Dickman, who was called in to help with the Mosquito fire, said in the video that crews were working to remove extremely parched brush from the base of the trees and will conduct a planned burn in the grove to try to protect the seven mature and six younger sequoias in the area known as the Placer Grove of Big Trees.

While wildfires are a natural part of the giant sequoia life cycle, extreme flames that topple the tall trees have proved deadly, especially in recent years as climate change intensifies the blazes.

“Because of the fuels and the dryness of them, these flames are overtopping these trees and they just can’t survive that,” Dickman told OnScene.TV. “We’re prepping to burn it under our own terms and not let the fire come to us.”

Firefighters are battling the state’s largest blaze of the year from all angles, McLean said, with more than 3,600 people assigned to the Mosquito Fire. He hoped cooler temperatures and increased humidity Thursday would help operations, but said the fire remained intense — as did their fight.

“We’re using all our tools in the toolbox,” McLean said.


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