Climate change is narrowing the window for safe prescribed burns: study

While prescribed burns are a critical tool in wildfire prevention, warming climate conditions are restricting the window of time in which they can be safely deployed, a new study has found.

Kindled by highly trained firefighters, these controlled blazes help clear away excess dry plant matter that could otherwise catalyze what the study authors described as “a raging inferno.”

Such fires can only occur safely when the weather is not so damp as to prevent combustion, but also not so dry or windy that more vegetation would burn than planned, the authors noted.

But climate change is now reducing the overall number of days and shifting the times of year when prescribed burns can occur, according to the study, published on Tuesday in Communications Earth & Environment.

With scientists projecting warming of 2.0 degrees Celsius (3.6 degrees Fahrenheit) by 2060, the authors projected that these changes would reduce the number of days suitable for prescribed burns by 17 percent on average across the U.S. West.

Most declines, they found, would occur during the spring and summer, when the majority of controlled burns currently occur. Reductions in spring and summer could be up to 25 percent and 31 percent, respectively, according to the study.

On the flip side, however, the researchers determined that there could be a net increase of 4 percent in the number of favorable days for prescribed fires in the winter.

“Global warming will reduce the number of favorable days for prescribed fires throughout the American West,” first author Daniel Swain, a climate scientist at the University of California Los Angeles, said in a statement. 

“But winter in particular may emerge as an increasingly favorable time for prescribed burns if the relevant policy and staffing changes can be made,” he added.

Swain and his colleagues also identified variations by region, observing that in California, for example, the changes would be biggest in the coastal and southern areas.

Many places in those areas could lose a month of days suitable for prescribed burns, they found.

The northern parts of the Rocky Mountains, however, might enjoy a slight increase in the number of days when it would be safe to deploy such fires, according to the study.

As wildfires across the U.S. West continue to increase in intensity, tools like prescribed burns will only become more critical, the researchers contended.

But optimizing this tool requires agencies to plan ahead, particularly with regards to their firefighting work force, they argued.

“This paper is giving us advanced warning,” co-author Kristen Shive, an expert on prescribed fire at the University of California, Berkeley, said in a statement.

“Hopefully we can change policies to either extend those folks or create winter-specific crews,” Shive added.