Why setting forest fires on purpose prevents extreme blazes

Setting intentional forest fires and letting other low-severity ones burn can significantly lower the chances of extreme blazes torching those same areas in the future, according to a new study released Thursday, while reducing toxic smoke over time.

Those controlled blazes, known as prescribed burns, can offer fire protection for more than a decade, the researchers found in a paper published in the journal Science. The findings are the latest in a robust body of research showing how managed fires can reduce the chances of megafires.

“The benefit you get is pretty dramatic,” said Marshall Burke, a professor at Stanford University’s Global Environmental Policy program in the Doerr School of Sustainability and one of the study’s co-authors. “We estimate that if you did a prescribed burn today, the likelihood that you would get extreme wildfire in that area where you burned tomorrow is down by about 90 percent. That is a really dramatic reduction in the probability of extreme fire.”

Still, prescribed and managed burning has long been a contentious practice. While about 99 percent of these operations remain contained, there have been instances where flames have escaped and erupted into disaster.

The study comes at a time when the United States has looked to shift how it manages its forests and responds to wildfire. Under the Trump administration, federal land management agencies have lost scores of staff, the U.S. Forest Service is undergoing a significant restructuring, and firefighters are transitioning to a new, unified firefighting agency.

In an example of broader efforts to overhaul how the nation fights wildfires, House Republicans last year introduced a bill requiring federal firefighting agencies to put out blazes within 24 hours. That’s an example of what’s called a “suppression” strategy, which aims to put fires out quickly after they erupt.

But in their new paper, the authors say such a practice creates a “fire paradox, in which putting out fires today can create larger fires in the future.” Climate change has exacerbated this reality by drying out fuels, the study says. And the findings suggest that the advantages of controlled and prescribed burning far outweigh the risks.

Using satellite imagery to take a bird’s-eye view of California and nearly all its wildfires over the past two decades, Burke and the lead author of the new paper, Iván Higuera-Mendieta, found that intentional burning dramatically reduced the severity of fires during those years. Managing low-severity fires across 1 million acres a year - a target for California - would reduce the amount of land that burned from severe fires by about 25 percent. And that protection stretched for about three miles.

The most notable results would come in conifer forests, which dominate nearly 60 percent of California’s forestlands. The researchers found that controlled burning treatments reduced the risk of any severe wildfire by nearly 53 percent. The evidence was more mixed for other types of vegetation, such as chaparral and shrublands, but if firefighters were able to keep fires from rapidly spreading into those fire-prone environments by creating burn scars, that could lessen the chance of a fire turning into a megablaze.

The prescribed burns ultimately also help improve air quality, the researchers found. For example, if California burned 500,000 acres of wildlands in one year, there would initially be more smoke in the air, according to the scientists’ modeling. But the state would reduce long-term smoke exposure by 10 percent over a decade.

In California, nine of the 10 largest fires in the state’s recorded history have occurred in the past decade. In 2020, the lightning-sparked fire around Mendocino National Forest shattered many experts’ and firefighters’ understanding of what fire can do. The August Complex fire grew into California’s first “gigafire” in modern history, a term for a colossal blaze that burned more than 1 million acres. That year, wildfires consumed about 4 million acres across the state, turned skies orange up and down the coast, and sent smoke as far as New York.

In their study, the researchers found that not only did prescribed burning drastically cut the chances of major wildfires sweeping through, but it also had what is known as a spillover effect.

“So if I burn in my yard, it not only benefits me,” Burke said. “I also benefit you, my neighbor, because if a fire blows through my yard and it burns at lower severity, that means you’re less likely to burn.”

The researchers first worked to identify how these spillovers changed the outcome of fires at large scale.

If firefighters purposefully burn one acre of a dry forest riddled with undergrowth and fuels, then that carries benefits up to about 3.1 miles away.

“And that’s great from an air-quality perspective, because that means you sort of get the benefits for free from a smoke perspective,” Burke added. “You can reduce burning, but you didn’t have to pay the initial smoke cost up-front.”

Lenya Quinn-Davidson, director of the University of California Agriculture and Natural Resources Fire Network, said the research bolsters “what we already know: If we let more low- to moderate-severity fire exist on the landscape, we would have less-severe fires,” she said. “We can’t thin every forest that needs thinning or prescribed-burn every acre that needs burning, so how do we plan for and leverage opportunities to get more beneficial wildfire on the landscape?”

In a conifer forest filled with drought-stricken and diseased trees and undergrowth, setting a controlled blaze, or letting one burn that is at low to moderate intensity, could curb the intensity of a future fire, too.

“Low-intensity fire begets more low-intensity fire,” Quinn-Davidson said.

Some communities have pushed back against this approach, however, over concerns about smoke exposure and the risk of the fire spreading. There have been some incidents when a prescribed burn escaped, in part because of climate change, including when the Forest Service set an intentional fire in 2022 that turned into the largest and most devastating blaze in New Mexico’s history.

And while a large-scale, controlled fire is a vital fire management tool, it takes time, resources and personnel to carry out, along with navigating strict local and state environmental regulations. In 2022, California Gov. Gavin Newsom (D) set an ambitious goal to expand the state’s use of controlled fires, which had averaged about 30,000 acres a year, to 400,000 acres a year by 2025. After last year’s massive Los Angeles fires, Newsom fast-tracked hundreds of projects to expand prescribed fire.

Yet the state has failed to meet its target: From 2024 to 2025, firefighters completed 63,551 acres of prescribed fire. And the state’s direct investment in forest management has been significantly reduced, from $1.1 billion in 2022 to $620 million for 2026.

Federal land management agencies have struggled to complete prescribed burning targets in recent years, in part a result of staffing shortages, retention issues and a need to direct much of their resources to worsening wildfires.

In a statement, the Forest Service said that the ongoing reorganization has not reduced the federal firefighters’ commitment to prescribed fire projects.

“Prescribed fire provides a massive return on investment by reducing future suppression costs, infrastructure losses and long-term recovery needs, which is why this work remains one of our highest priorities,” the agency said.

The Forest Service has a yearly goal of reducing dangerous fuels across 3.6 million acres, “with about 1.5 million of those acres consistently coming from prescribed fire.”

In 2024, the agency burned 2.1 million acres to reduce dangerous fuels, following in 2025 with 1 million fewer acres of prescribed burns, at 1.1 million. So far this year, the Forest Service said, it has treated nearly 2 million acres.

After publication of this article, the U.S. Wildland Fire Service responded to questions from The Washington Post, stating that having a unified agency within the Interior Department will enable the administration to have “significantly more USWFS firefighters available to complete” fire-related work, including prescribed fire and other hazardous fuel removal projects that will help prevent future megafires.

The agency said its approach “will be beneficial for the environment and will help prevent future megafires without the added risk to our communities that ‘beneficial fire’ represents.”

In their research paper, Higuera-Mendieta and Burke highlight how fire-suppression practices have helped “to increase the occurrence of larger and more extreme wildfires.”

Some experts worry that the U.S. is further embracing that strategy.

In an April letter, Agriculture Secretary Brooke L. Rollins said, “This fire season we are prepared to continue our full suppression strategy to suppress fire starts quickly to protect our forests and rural communities.”

Rollins also said that the agency’s goal was to “expand hazardous fuels treatments using both mechanical means and prescribed fire to reduce landscape vulnerabilities, where conditions allow.”

Still, Quinn-Davidson and other experts worry that touting a full-suppression strategy is shortsighted.

She added, “Why do we keep doing something that keeps making the problem worse?”

Steve Ellis, who served as deputy director of the Bureau of Land Management as well as in the U.S. Forest Service, agrees.

“It’s important to keep all tools in toolbox for wildland fire management,” Ellis said. “We will not suppress our way to success in dealing with catastrophic wildfire in this country.”