Forest managers set this prescribed burn in California's Stanislaus National Forest.

Forest managers set this prescribed burn in California's Stanislaus National Forest. Eric Knapp/U.S. Forest Service

Fighting Fire with Fire: California Turns to Prescribed Burning

A century of fire suppression and historic drought have combined to kill 129 million trees and counting in California’s forests. As wildfires rage across the state, managers are increasingly setting fires to burn the dead timber and ward off catastrophe.

Adam Hernandez walked across a blackened woodland past logs smoldering near Shaver Lake, 200 miles north of Los Angeles in the Sierra National Forest. With each step, gray ash puffed from under his heavy boots, and tiny flames flickered through a thick layer of pine needles on the forest floor.

Hernandez, 37, is an elite firefighter who served 13 years on smoke-jumper and hot-shot crews battling some of the most intense wildfires in the American West. Now, as a Sierra National Forest fire management officer, his job is setting small fires like this one to halt an epidemic that has so far killed nearly 129 million trees on 9 million acres — an area the size of Switzerland.

Caught in the crosshairs of climate change and a century of poor forest management, the Sierra Nevada — a region that provides 60 percent of California’s water supply — is becoming a tinderbox of dead wood. The 1.2 million acres still smoking statewide include the 96,901-acre Ferguson fire, which forced the closure of Yosemite National Park for three weeks. The wildfires that have already killed 14 people and destroyed more than 1,000 homes in California this year follow the state’s deadliest wildfire season in 2017, when 1.3 million acres burned, 49 people died, and over 10,000 structures were razed.

Too little precipitation during California’s five-year drought, which ended in 2017, has left trees weak and vulnerable.

In the Sierra Nevada, a 400-mile range of tilted granite along the state border with Nevada, entire mountainsides have turned red and gray with the dying needles of ghostly, water-starved trees. Left alone, the dead trees now standing will rot and fall, tumbling one on top of another like piles of gigantic pick-up sticks. Scientists say this tangled mass of timber represents a fire hazard of unprecedented size and intensity.

With the Sierra’s zombie-like trees ready to start dropping, land managers are racing to remove the dead wood before it ignites or crashes onto houses or roadways. More than a million trees have so far been felled, overwhelming sawmills and biomass plants. But an estimated 127 million and counting remain, threatening the region with fires of such ferocity that some scientists have compared the potential heat to World War II firestorms at Dresden and Tokyo.

A century of fire suppression has produced too many trees — in some places five times the historic number, explained Malcolm North, a U.S. Forest Service scientist with the Pacific Southwest Research Station. And too little precipitation during the state’s five-year drought, which ended in 2017, has left these trees weak and vulnerable. The combination has been deadly, he said. “We just have too many straws in the ground for a very limited amount of water.”

A prescribed burn, intended to clear dead trees that fuel intense wildfires, smolders in Sierra National Forest in May 2018. 

A prescribed burn, intended to clear dead trees that fuel intense wildfires, smolders in Sierra National Forest in May 2018.  USDA/US Forest Service, Sierra National Forest File

Hernandez began noticing an increase in the number of dead trees in 2013, two years into the drought. In 2014, he started taking time-stamped photos to chart the mortality. He could see a dramatic difference in the span of just two months. A stand of copper-colored trees spotting a hillside suddenly expanded into an unbroken mantle stretching ridge after ridge to the horizon. By 2016, the die-off had killed nearly 90 percent of the Sierra National Forest’s pines, leading forest managers to refer to the region as “mortality central.” That level of loss was “a total game changer,” said Hernandez, who now faces the daunting task of trying to halt, or at least slow, the collapse. “We can’t be cavalier about anything,” he said. “Time is against us.”

The scale of the dead-tree emergency has created widespread consensus about a management tool as counterintuitive as it is familiar: fire. An ecological process as essential as sunshine and rain, state and federal officials and conservationists now agree that fire is crucial to the Sierra forests’ future in order to jumpstart natural regeneration and reduce the threat of even more wildfires.

Politicians and agency and timber industry officials have long argued that the best way to reduce this woody buildup is to log, and that is one of the tools being used. But the sheer acreage, mostly in inaccessible backcountry, has forced the realization that setting prescribed fires in areas of high tree mortality is the best option to lessen future fire danger. 

As the planet warms and areas vulnerable to wildfire double, the use of prescribed fire is increasing nationwide.

“If we do nothing we’re going to have much more severe fires, more smoke, and potential damage,” said Scott Stephens, a fire science professor at the University of California, Berkeley. “There isn’t a no-fire option.”

Historically, fire charred 553,000 acres annually on federally managed Sierra forests, according to scientific reports. Today both state and federal agencies are setting progressively ambitious goals toward returning natural fire to the landscape. Supported by organizations as disparate as the Sierra Club and the California Forestry Association, the U.S. Forest Service, the California Department of Forestry and Fire Protection, and the Sierra Nevada Conservancy signed a 2015 memorandum endorsing expanded use of fire.

The Forest Service goal for California in 2019 is 250,000 acres of fire and “mechanical thinning,” which is using equipment to remove smaller trees. The California Department of Forestry set 60,000 acres as this year’s target for prescribed fire and other fuel-reduction efforts on non-federal lands, with 500,000 acres as a goal using logging and forest thinning as well as fire. “Those targets are what’s required to make an ecologically meaningful difference,” says Helge Eng, California’s deputy director of resource management. Governor Jerry Brown allocated $256 million to support these efforts.

Dead pines, their needles turned orange by California's historic drought, cover a slope at the edge of Sequoia National Park. 

Dead pines, their needles turned orange by California's historic drought, cover a slope at the edge of Sequoia National Park.  Jane Braxton Little

As the planet warms and the areas vulnerable to wildfire double, threatening to convert forests from carbon sinks to emitters, land managers are increasing the use of prescribed fire nationwide. All states but Hawaii are now using it as a tool to reduce wildfire danger and to enhance biodiversity by restoring habitat for fire-adapted species. Florida leads the way, burning more than 2 million acres last year. Arizona and New Mexico set intentional fires on just over 570,000 acres in 2017, while Oregon, Montana, Idaho, and Colorado joined California in burning a combined 169,000 acres.

Among Western states, California faces the most arduous challenge in managing intentional fires: Two million homes are now located in the state’s wildfire-prone areas. Even though prescribed burns produce less air pollution than wildfires, any smoke generates loud, persistent complaints — and for good reasons: A recent American Heart Association study found wildfire smoke raises the risk of heart attack 42 percent above smoke-free air. A 2015 study published by the American College of Allergy, Asthma, and Immunology reported a 16 to 26 percent increase in the use of relief medications in a sample of 6,160 asthmatic children after southern California wildfires in 2003 and 2007.

Fortunately, air emissions technology is evolving nearly as quickly as California’s urgency to prepare for more infernos. Using portable air pollution monitors and weather stations, combined with modeling satellite images of smoke plumes, fire technicians are increasingly able to determine the greatest concentrations of smoke and where the plumes are headed. That allows firefighters to adjust how they’re managing the blaze to limit pollution. Using prescribed fires strategically can actually protect public health by reducing out-of-control fires, said Craig Thomas, conservation director for Sierra Forest Legacy, thus lowering concentrations of smoke pollution.

In the Sierra National Forest, managers design each prescribed fire to balance public safety with ecosystem benefits.

But other hurdles remain, some within the very institutions promoting increased fire use. The state and federal employees doing the actual burning are often among the 7,000 full-time firefighters putting out wildfires, limiting their availability during the best times for planned ignitions. And although just 1 percent of these prescribed fires have escaped nationally, many managers remain reluctant to risk their reputations with a management tool that may go rogue, Thomas said.

In the Sierra National Forest, Hernandez designs each prescribed fire to balance public safety with ecosystem benefits. He stopped beside a grove of three-foot diameter ponderosa pines in the midst of a recent 500-acre ignition. Under natural conditions, fires would blaze here as often as every seven years, keeping ground litter and dense undergrowth in check. He and his crew lit this plot in February to mimic natural fire, leaving sparse undergrowth and charred patches running six feet up the trunks of the ponderosas.

Hernandez scuffed his boot against a clump of grasses poking through the ashy soil. Previously, the seeds on the burn site couldn’t penetrate though the mat of dead material to produce the forbs deer, bears, and other wildlife need for foraging. “Now they can,” he said. Hernandez also strives to keep fires from getting too hot, which kills seedling trees. He reached for the tip of a seven-foot pine seedling, bending it down to show a plump bundle of green among the scorched needles. “And here’s our new forest,” he said.

Adam Hernandez examines a young pine tree four months after a prescribed fire in the Sierra National Forest.

Sierra National Forest fire management officer Adam Hernandez examines new growth on a young pine tree four months after a prescribed burn. Jane Braxton Little

With wildfires still burning across California, most prescribed burning is on hold now.  But by the end of December, Hernandez said he aims to burn 2,000 acres on the Sierra’s western slopes just south of Yosemite. That will add to the nearly 125,000 acres of managed fires on national forests in California so far this year. The acreage is a trifle compared to the lands now burning out of control, but it’s a start toward the safe return of natural fire. Each ignition is strategically placed to anticipate where a wildfire will likely come from, eventually connecting one burn with another to form a mosaic where fuels can be reduced enough to disrupt the progress of an uncontrolled wildfire.

“We’re going to cover as much ground as we can,” Hernandez said. “You just keep building like blocks in a foundation.”

Buoyed by the state’s new perspective and commitment to prescribed fire, Hernandez is optimistic that an aggressive burn program will give forests a chance to start over without the catastrophic wildfires now blazing. But he knows all too well that saving this and other California forests requires recreating the forest foundation that has been dismantled through mismanagement and climate change. One challenge will be whether enough crews can burn enough acres before the zombies fall. 

Travel for this article was made possible by an award from the Institute for Journalism and Natural Resources.