Controlled burns in California could reduce risk of catastrophic wildfire by 60 percent 

Deploying low-intensity burns could reduce the initial risk of catastrophic wildfire by more than 60 percent, while helping protect the area for at least six years, a new study has found.  

To be effective, wildland fuel treatments need to occur in an ongoing, period manner, as opposed to a one-time intervention, according to the study, published Friday in the journal Science Advances. While previous work has demonstrated that California needs either prescribed burns or vegetation thinning on about 20 percent of the state’s lands, researchers had yet to quantify the precise value of such activity. 

Reaping the rewards of the risk reduction project — including prescribed blazes, managed wildfires and tribal cultural burning — requires careful selection and targeted intervention efforts, the scientists found. 

“Beneficial fire is not without its own risks,” co-author Michael Wara, director of the Climate and Energy Policy Program at the Stanford Woods Institute for the Environment, said in a statement. 

“But what our study shows is just how large and long-lasting the benefits are of this crucial risk reduction strategy,” Wara added. 

Indigenous communities for millennia allowed wildfires to burn and intentionally applied fire to their lands, both for ceremonial and subsistence purposes, according to the researchers. These pre-colonial practices meant that California forests contained less fuel for flames and helped the ground retain moisture, the authors explained.

To draw their conclusions, the authors reviewed 20 years of satellite monitoring data for wildfires that occurred over more than 25 million acres of California forests. 

The team of researchers — which included fire policy, public health, statistics and machine learning experts — harmonized multiple statewide datasets on fire intensity and severity, calculated by the amount of energy released and ecosystem impacts, respectively.   

They then measured the protective impact of low-intensity fires by assembling unburned spaces into a synthetic landscape closely mirroring attributes of the areas that were burned. The landscape included characteristics such as weather patterns, elevation, vegetation type and disturbance history, according to the report. 

Using this approach, the authors were able to evaluate how the burned landscapes might have evolved in a given year had they not encountered low-intensity fires during that period. 

They observed that in conifer forests, areas that have recently burned at low intensity were 64 percent less likely to burn at high intensity the following year, when compared with unburned synthetic control zones. 

Their findings in hardwood forests were similar to those in conifer forests, except with weaker statistical significance, which the authors in part attributed to a smaller sample size.

The researchers expressed hope that their study could serve as a foundation for future assessments of wildland fuel treatments, such as cost-benefit analysis of their implementation. 

The timing, they explained, is particularly opportune, as the U.S. Forest Service has proposed protecting about 50 million acres over the next decade, through a combination of fuel treatment strategies. 

Study lead author Xiao Wu, an assistant professor of biostatistics at Columbia University, emphasized the important roles that both data science and multidisciplinary collaborations can play in climate change mitigation efforts.

“Wildfires present substantial threats to both our ecosystems and human well-being,” Wu said in a statement. “As scientists, our constant goal is to find practical solutions.”