Controlled burns reduce wildfire smoke by 14%

According to a study published in AGU Advances led by Stanford University, prescribed burns can reduce wildfire severity by 16% and reduce smoke pollution on average by 14%.

The study provides the first comprehensive evidence that combustion works were controlled in practice in the Western United States, analyzing satellite data from 186 combustion sites, and later experiencing wildfires during the catastrophic 2020 fire season.

“In theory, fires are often used as a promising tool to suppress the effects of wildfires, but we show clear empirical evidence that burning works are prescribed in practice,” said Makoto Kelp, a postdoctoral researcher at the Doerr School of Sustainability at Stanford University. The finding is nearly $2 billion in federal funding allocated to hazardous fuel reduction treatments.

Real-world fire strategy analysis

Using high-resolution satellite images, land management records and smoke emission data, the researchers compared the areas of fires that were fired between late 2018 and spring 2020 to adjacent untreated areas. The subsequent burning during the extreme fire season of 2020, both areas burning, allowing scientists to measure the protective effects of controlled burns.

This study addresses key knowledge gaps. Although experts have long believed that prescription burns are effective, there is little research on quantitative welfare, and public opinion remains different due to concerns about smoky air and escaping fires.

Key Discovery

The analysis reveals several important modes:

• The prescribed fire produces only 17% of the smoke generated by wildfires in the same area
• Fire treatment is better in forests than in bushes or barren areas
• Controlled burns are much better than mechanical sparse when reducing the severity of fires
• The treatment is poor in the interface area of ​​wilderness city

In the wilderness-city interface areas, the severity of fires has decreased by only 8.5%, while in areas far from human development is 20%. This difference reflects the cautious approach that institutions must adopt near population and infrastructure, although these areas are policy priorities.

The benefits of smoke pollution

“People often think of wildfires in terms of flames and evacuation,” explains Marshall Burke, an associate professor at Stanford. “But smoke is a silent and far-reaching danger, and prescription fires may be one of the few tools to actually reduce total smoke.”

The fine particulate matter of wildfires is associated with respiratory and cardiovascular problems and is increasingly driving poorer air quality across the country. Researchers estimate that if California treats 1 million acres annually with prescribed fires, it could reduce particulate emissions by 655,000 tons over five years, equivalent to more than half of the state’s total catastrophic smoke suffered during the 2020 wildfire season.

Policy Impact

The quasi-experimental design of the study addresses concerns about the prescription burning of smoky air. Although controlled burns do produce smoke, studies show that they create net benefits by preventing large emissions of future wildfires.

“We already know that the population is growing the fastest in the wild world interface areas where vegetation is most sensitive to wildfire risk,” noted Noah Diffenbaugh, a climate scientist and study co-author of Stanford. “So, understanding why prescribed fire treatments are less effective in these areas is a key priority for effectively managing this aggravated risk.”

Currently, California has only prescribed approximately 30,000 acres of land each year through CAL fires, with its stated target of 400,000 acres by 2025.

Research limitations and future research

The researchers acknowledged that their findings may represent conservative estimates of prescribed fire welfare, as treatment can have a protective spillover effect on surrounding untreated areas. The analysis focuses on fires that occur within two years of prescribed burns, but long-term benefits may be greater.

The study also highlights the complexity of implementing effective prescribed burns in densely populated areas, and despite its safety, a mixed approach and prudent regimen may reduce the therapeutic effect.

“This empirical evidence is crucial for effective policies,” Heerp concluded. “My hope is that it helps inform the conversation around prescription fires, a potential wildfire mitigation strategy in California.”

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