After Years of Research, Expert Advice: Burn California's Forests

The findings of a 20-year study on the health of California forests will come as no surprise to Native Americans, whose ancestors traditionally managed land through controlled fires. The study out of the University of California-Berkeley confirms that prescribed burning, the use of controlled fire to clear debris; restoration thinning, in which slow-growing or damaged trees are removed to make space for others; or a combination of both strategies effectively reduce the risk of catastrophic wildfire while also improving forest health, according to a release. Researchers spent two decades investigating the strategies at the 4,000-acre Blodgett Forest Research Station on the unceded lands of the Nisenan Tribe to determine whether they could be safely implemented across the state, whose dense forests provide excellent wildfire fuel.

Researchers divided up 12 plots: three managed using prescribed burns, three managed through restoration thinning, three managed through a combination of those strategies, and three control plots that humans ignored except to suppress fire. After 20 years and three prescribed burns, researchers surveyed the land, estimated how many trees were likely to survive wildfire, and determined how strongly trees had to compete for resources. All of the noncontrol plots showed greater resiliency to wildfire, with "an 80% likelihood that at least 80% of trees would survive," per the release. Both prescribed burning and restoration thinning also limited competition, making trees more resilient to stressors like drought and bark beetles, though restoration thinning had the added benefit of being financially covered by revenue from timber.

Trees in forests managed with a combination of the strategies appeared most resilient to stressors, however. "When you combine thinning with fire ... it speeds up the timeline for achieving a more resilient structure," says study co-author Ariel Roughton of Berkeley Forests. Still, all three treatment strategies are "very effective," says Scott Stephens, a professor of fire science and lead author of the study published in Ecological Applications. "I hope this lets people know that there is great hope in doing these treatments at scale, without any negative consequences." Berkeley Forests notes that "while treatments may result in a short-term release of carbon, significant carbon sequestration benefits occur following treatments because of long-term storage in forest products, reduced wildfire emissions, and increased growth of residual trees." (More forests stories.)