Stanford study finds prescribed fire can cut wildfire smoke for years
A Stanford study in Science finds prescribed fire on 500,000 acres a year of California conifers could cut wildfire smoke about 10% over a decade.
Photo by Tom Fisk on Pexels
Expanding prescribed fire across California’s conifer forests could cut the deadly fine-particle pollution from wildfire smoke by about 10% over a decade, a Stanford-led study reports. The paper, published on 11 June 2026 in the journal “Science” by Iván Higuera-Mendieta and Marshall Burke of the Stanford Doerr School of Sustainability, draws on two decades of satellite data and finds that deliberately set, low-severity fire lowers the risk of later catastrophic blazes both where it burns and for miles around.
The central figure: treating 500,000 acres of conifer forest each year with controlled burns could reduce dangerous smoke PM2.5 by roughly 10% over ten years, and by 20 to 25% in the worst fire years. That treatment scale is about four times the area currently burned under management across all California wildlands, and slightly above the state’s own annual goal.
How the prescribed fire study measured fire and smoke
The researchers built satellite-derived measures of fire severity for 98.9% of California wildfire events recorded by the federal Monitoring Trends in Burn Severity programme between 2000 and 2021. They paired those with fire-specific estimates of smoke PM2.5 — the fine particles that lodge deep in the lungs and pass into the bloodstream — for 2006 to 2020. Because large-scale prescribed burning has been too rare in the U.S. West to study directly, the team used low-severity wildfires as a stand-in for the kind of managed fire that land agencies want to reintroduce.
Higuera-Mendieta, a PhD student in Earth system science and the study’s lead author, said the design lets the analysis span “decades of fires, burning in different landscapes under very different conditions.” Burke, a professor of environmental social sciences and senior author, framed the contribution plainly: “Our contribution is to put some numbers on these trade-offs.”
The scale of the gap between managed and uncontrolled fire is stark in the team’s own accounting.
When does prescribed fire reduce wildfire smoke?
The study describes what it calls a new fire paradox. A century of fire suppression has left forests packed with dead wood, brush, and small trees that fuel today’s extreme blazes; bringing back low-severity fire reduces that fuel, but the controlled burns produce smoke of their own. The question land managers face is how much pollution now is worth tolerating to avoid worse smoke later.
The data give a clear answer for conifer forests. Low-severity fire immediately cut the risk of a very severe wildfire in the same place by 92%, with the benefit lasting up to a decade and reaching as far as 5 kilometres — about 3 miles — beyond the burned ground. “You get large benefits in the place that you treated,” Higuera-Mendieta said, adding that nearby unburned areas gain protection “for free.” In shrublands the effect faded within four years and did not clearly lower the risk of the most severe fires.
In simulations that added more low-severity fire to the landscape from 2010 onward, treating 500,000 acres a year raised smoke PM2.5 by about 50% in the early years, when wildfire activity happened to be low, but turned into a net reduction as early as year four. Over the full decade the cut reached about 10%, and was largest in 2020 and 2021, the worst smoke years on record in California. Even under high discount rates, the air-quality benefit outweighed the cost of prescribed-burn smoke by about 5 to 1 over a decade.
The headline numbers from the study are collected below.
| Measure | Value |
|---|---|
| Immediate cut in very-severe-fire risk (treated conifer areas) | 92% |
| Spillover benefit beyond the burned area | up to 5 km (≈3 miles) |
| Duration of reduced risk | up to a decade |
| Modelled treatment scale | 500,000 acres of conifer forest per year |
| Smoke PM2.5 cut over a decade at that scale | about 10% |
| Smoke PM2.5 cut in the most active fire years | 20–25% |
| Early-year smoke increase before the net benefit | about 50% |
| Year the net benefit begins | year 4 |
| Air-quality benefit-to-cost ratio over a decade | about 5 to 1 |
| Fuel-treatment cost cited | about $170 per acre |
| Share of California wildfire events measured (2000–2021) | 98.9% |
Source: Higuera-Mendieta and Burke, “Science”, 11 June 2026; Stanford Doerr School of Sustainability.
Limits and what comes next
The authors are clear about what the work does not cover. It does not translate the modelled smoke changes into avoided asthma attacks, heart problems, or deaths, and it does not count the direct cost of fuel treatments beyond citing a figure of about $170 per acre, which varies with terrain and distance from towns. It also does not compare prescribed fire with lower-emission options such as mechanical thinning. The simulations assume untargeted treatment spread across California’s roughly 20 million acres of conifers, rather than focusing on the places most likely to burn.
The wider driver is a warming climate, which dries vegetation and lengthens fire seasons, raising the odds of the catastrophic fires the treatment is meant to head off. Winss Solutions has set out the emissions picture behind that trend in its overview of the status of carbon emissions in China, the USA and Europe, and the policy response in its explainer on the EU’s “Fit for 55” climate package. The Stanford team is now linking its smoke estimates to local air-quality records to gauge health effects, and to guide where prescribed burns would do the most good.
Background: prescribed fire and wildfire smoke
For most of the twentieth century, U.S. fire policy aimed to put out wildfires quickly. That approach reduced burned area in the short term but allowed fuel to build up in forests that evolved to burn at regular intervals, setting the stage for larger and hotter fires. Smoke from those fires now exposes millions of people across the American West to fine particulate pollution that can travel thousands of miles. Fire scientists have long argued for reintroducing “good fire” — low-severity burns set under controlled conditions — to thin fuels, and earlier work had shown that treated patches tend to burn less severely afterwards. What had been missing was an estimate of whether the smoke saved outweighs the smoke added across a whole region and many years. The new “Science” study, supported by the Keck Foundation and a Stanford Data Science fellowship, supplies that accounting and points to conifer forests as the place where expanded prescribed fire would deliver the clearest air-quality gains.
Sources: Science; Stanford Doerr School of Sustainability; Phys.org
Featured image: photo by Tom Fisk on Pexels (free Pexels license).
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I specialize in sustainability education, curriculum co-creation, and early-stage project strategy. At WINSS, I craft articles on sustainability, transformative AI, and related topics. When I’m not writing, you’ll find me chasing the perfect sushi roll, exploring cities around the globe, or unwinding with my dog Puffy — the world’s most loyal sidekick.
