After decades of suppressing wildfires in California, researchers are finding that controlled burning can play a key role in forest management. A new long-term study led by scientists at the University of California, Berkeley, has shown that while prescribed burns release carbon dioxide in the short term, they help maintain large, fire-resistant trees and may boost forests’ ability to store carbon over time.
“Over time, we found that the productivity of unmanaged tree stands decreased, likely due to increased competition and climate stress. Meanwhile, prescribed burning helped maintain large, fire-resistant trees, eventually increasing the productivity of these stands,” said study lead author Yihong Zhu, a graduate student at UC Berkeley. “We wouldn’t be able to detect such a benefit had we not been able to monitor these stands over 20 years and three entries with controlled fire.”
The research offers guidance for policymakers and land managers working toward reducing wildfire risk while helping California reach its goal of net zero carbon pollution by 2045. According to John Battles, senior author of the study and professor of forest ecology at UC Berkeley: “Nature-based climate solutions were a big focus of the 2024 Paris Climate agreement, and either maintaining or increasing forest carbon is one of the most cost-effective strategies. We found that, with some management, you may lower the total carbon storage of a forest, but you make it safer from loss from wildfires or pathogen outbreaks. We call it stable carbon.”
The experiment began in 2000 at Blodgett Forest Research Station in the Sierra Nevada. Researchers used different techniques—prescribed burning and restoration thinning—on various plots for two decades while leaving others untouched as controls. They tracked changes in carbon stored in everything from pine needles on the ground to thick tree trunks.
“We looked at big trees, we looked at little trees, we looked at shrubs, we looked at different fuel classes, and then we checked how they changed,” said Battles. “It really is just like a massive accounting job, except we’re not measuring money, we’re measuring carbon.”
Findings revealed that although control plots stored more total carbon overall during much of the study period because they were left undisturbed by fire or thinning activities; repeated prescribed burns increased net productivity nearly enough to offset initial losses caused by burning.
“After the first burn, the net productivity of those plots was really low and the controls looked a lot better,” said John Battles. “But by the third burn, the patterns had switched.”
Fire suppression has led to dense growths dominated by smaller trees like incense cedar and white fir—species whose presence increases wildfire risk because their foliage acts as ladder fuel leading flames up into treetops where fires become harder to control. Prescribed burns reverse this trend by promoting larger species such as ponderosa pine.
“We’ve always wondered if we could restore these ecosystems to a more functional state — lower density and more frequent fire — do we eventually see a bonus? Do we get that golden nugget? And in this work we were able to actually measure it,” said Scott Stephens—a co-author on this paper who also teaches fire science at UC Berkeley.
Earlier work from this team showed combining mechanical thinning with prescribed burns best reduces wildfire hazards but results in greater immediate releases of carbon compared with using only prescribed burns.
These findings provide communities with clearer information about trade-offs between reducing wildfire risks versus maximizing stored forest carbon. Where preventing fires is critical—for example near populated areas or sequoia groves—a mix of thinning plus burning might be preferred; elsewhere simply using prescribed fires could suffice for both health benefits and long-term climate goals.
“We’ve got to get these treatments out there,” Battles said. “Some treatments might be better than others in certain situations but now we’ve made trade-offs explicit so we can pick the right approach.”
Other contributors include Daniel Foster, Brandon Collins, Robert York, Ariel Roughton and John Sanders from UC Berkeley along with Emily Moghaddas from U.S Department of Agriculture Forest Service.
