Stanford study finds surprising upside of prescribed burns

As climate change drives up the chance of extreme wildfires, smoke pollution presents a real health risk for people in the West.

Read more Developers pitched a Calif. data center to fix this city’s woes, residents want anything else

But now scientists have documented how using prescribed burns — one of California’s leading strategies for mitigating wildfires — could actually reduce air pollution over time. 

In a study published in the journal Science on June 11, Stanford University researchers found that intentionally burning 500,000 acres of conifer forests in California every year could reduce wildfire smoke pollution overall by about 10% over a decade.

“This study highlights that yes, prescribed fire is good, but sometimes the benefits take a while,” Marshall Burke, a professor in the Doerr School of Sustainability at Stanford and the senior study author, told SFGATE. “As a species, we’re not that good at delayed gratification, but our numbers say in the end, it’s worth it.”

The study relied on two decades of satellite measurements of fire severity and smoke particulate matter across California. Reflecting similar findings in previous research, it documented that low-severity wildfires, a stand-in for prescribed burning, can cut the immediate likelihood of future severe wildfires in the same area by 92%. It found that smoke pollution from fires would initially rise with prescribed burning but begin improving overall after about four years.

California burns the study’s recommended 500,000 acres in prescribed burns, although the state’s goal is to incinerate about that much fuel every year. 

Michael Kleeman, a professor with the UC Davis Air Quality Research Center, was not involved in this study but is leading a project sponsored by the California Air Resources Board investigating similar questions. Kleeman emphasized the caveat, suggested by his early results too, that aggressive prescribed burning will improve public health during years with high wildfire activity but could be a detriment if there’s a year with few fires. Further, the regions that experience increases or decreases in smoke concentrations vary. 

“The air quality and public health benefits of prescribed burning are an incredibly complex question that cannot be answered by a single study or even a single group,” he wrote to SFGATE. “Much like climate change itself, it will take multiple groups and multiple studies to form a weight of evidence approach to estimate the benefits of prescribed burning.”