A 20-year experiment in the Sierra Nevada confirms that different forest management techniques — prescribed burning, restoration thinning or a combination of both — are effective at reducing the risk of catastrophic wildfire in California.
These treatments also improve forest health, making trees more resilient to stressors like drought and bark beetles, and they do not negatively impact plant or wildlife biodiversity within individual tree stands, the research found. The findings of the experiment, called the Fire Surrogate Study, are published online in the journal Ecological Applications.
"The research is pretty darn clear that these treatments are effective — very effective," said study lead author Scott Stephens, a professor of fire science at the University of California, Berkeley. "I hope this lets people know that there is great hope in doing these treatments at scale, without any negative consequences."
Last year, California announced a strategic plan for expanding the use of prescribed fire to 400,000 acres annually by 2025. However, the use of beneficial fire continues to be hindered by multiple factors, including the lack of a trained workforce, the need for specific weather conditions for burning, and fears about potential risks.
This study shows that restoration thinning is also a viable option for forest management and can be used in tandem with beneficial fire without harming forest health or biodiversity.
"Our findings show that there's not just one solution — there are multiple things that you can do to impact the risk of catastrophic fire," said study co-author Ariel Roughton, research station manager at Berkeley Forests. "Folks can choose from different combinations of treatments that might fit their needs, and we can show them how those treatments might impact things like wildfire behavior, tree growth and carbon holding in their forests."
UC Berkeley's Blodgett Forest Research Station is a model for how California can reduce the risk of severe wildfire and improve the ecological health of its forests. (UC Berkeley video by Roxanne Makasdjian and Jason Blalock)
Surrogates to wildfire
Over the past two decades, Stephens and other researchers at Berkeley Forests have used prescribed burning, restoration thinning or a combination of both to treat plots of land at Blodgett Forest Research Station, a 4,000-acre experimental forest located about 65 miles northeast of Sacramento on the unceded lands of the Nisenan peoples.
The Fire Surrogate Study was one of 13 studies across the U.S. first launched in 1999 with funding from the U.S. Joint Fire Science Program. Its aim was to study whether the two treatments could mimic the beneficial impacts of lightning fires and Indigenous burning practices on California's forests, which have become dense and overgrown after a century of logging and fire suppression.
"Prescribed fire and restoration thinning are both surrogates for wildfire, a key process that happened frequently in California before European colonization," Stephens said. "The impetus of this study was: If you're going to implement these treatments at a large scale, is there anything that's going to be lost?"
The study created nine experimental plots and three control plots at Blodgett. Three of the experimental plots were managed only using prescribed burns; three burns occurred over the course of 20 years. Three other experimental plots were first thinned and then burned, and the final three were treated only with restoration thinning. The control plots were left to grow without human interference except continued fire suppression.
At the end of the 20-year period, the researchers surveyed the vegetation in each plot and used computational modeling to estimate how many trees were likely to survive wildfire. They found that all three types of experimental plots were significantly more resilient to wildfire than the control plots, showing an 80% likelihood that at least 80% of trees would survive.
They also calculated the "index of competition," a measure of how strongly trees must compete for resources like sunlight, water and soil nutrients. By removing excess trees and vegetation, thinning and burning both limited the amount of competition between trees, making them less vulnerable to stressors, like drought and bark beetles.
However, the plots that were treated with a combination of thinning and fire had the best index of competition, suggesting that they would be the most resilient to the impacts of climate change.
"When you combine thinning with fire, you're able to modify all different levels of the forest structure, and it speeds up the timeline for achieving a more resilient structure," Roughton said.
Restoration thinning can also provide financial benefits: Often, larger trees can be sold to sawmills, and the proceeds can be used to help offset the cost of forest management. Over the course of 20 years, the treatments at Blodgett were entirely paid for by revenue from timber.
"When I go to Sacramento and talk about [forest management] with legislators, the first question they always ask is about cost," Stephens said. "People in the state government are telling us that they can't be the sole source support for this work. That's why the economics are so important."
In September 2022, the forests at Blodgett were subjected to a real-life test: On the morning of Sept. 9, 2022, the Mosquito Fire breached the north side of the property, burning approximately 300 acres before it was contained two days later.
One of the study's control plots was located directly in the path of the blaze, and more than 60% of the trees in this plot were completely scorched. However, neighboring experimental plots that had been treated with prescribed burns served as “fuel breaks,” burning less hot than the control and acting as staging areas for firefighters.
"We think that, overall, our management actions, coupled with the weather, did have a pretty big impact on the behavior of the fire," Roughton said.
The researchers have received a four-year grant from the Joint Fire Science Program to continue the Fire Surrogate Project. With the help of the grant, they have established a new control plot to replace the one that burned and plan to apply a fourth fire to the experimental burn-only plots.
They are also collaborating with the United Auburn Indian Community to reestablish Indigenous cultural burning at Blodgett.
"We want to be part of the solution, and that's part of our mission at Blodgett," Roughton said. "We hope that by doing these studies and bringing folks here to see the effects of the different treatments, they will take that back and apply it to the land that they're going to be managing."
Additional co-authors of the study include Daniel E. Foster, John J. Battles, Alexis A. Bernal, Brandon M. Collins, Rachelle Hedges and Robert A. York of UC Berkeley and Jason J. Moghaddas of the Spatial Informatics Group. This project was originally funded by the U.S. Joint Fire Science Program, and it has received additional support from the California Fourth Climate Change Assessment, the McIntire-Stennis Program, the California Greenhouse Gas Reduction Fund, and the UC Office of the President's UC Laboratory Fees Research Program. Smart Practices and Architecture for Prescribed Fires in California was also important to keeping this long-term project active.
Study highlights 4 strategies to overcome barriers to prescribed fire in the West
Prescribed fire, which mimics natural fire regimes, can help improve forest health and reduce the likelihood of catastrophic wildfire. But this management tool is underused in the fire-prone U.S. West and Baja California, Mexico, due to several barriers.
A paper from the University of California, Davis, pinpoints those obstacles and suggests four key strategies that policymakers and land managers can take to get more “good fire” on the ground in North America's fire-adapted ecosystems. The paper also provides examples of how people are surmounting some of these obstacles.
“Prescribed fire is one of the most important tools we have for restoring natural fire regimes and undoing the effects of a century of fire suppression,” said lead author John Williams, a project scientist with the UC Davis Department of Environmental Science and Policy. “But there are a number top-down barriers at the upper levels of management that keep us from growing the workforce and getting burns done at the scale and extent needed. We point out some of the big ways that agency leaders and policymakers can dismantle those barriers and empower the full range of people capable of doing this work, from burn bosses and citizen-prescribed burn associations to nonprofits and tribal groups.”
The paper, published in the journal Frontiers in Ecology and the Environment, centers on the North American Mediterranean climate zone, which includes most of California, southwestern Oregon, western Nevada and northern Baja California in Mexico. Lenya Quinn-Davidson, director of UC Agriculture and Natural Resources' Fire Network, is a co-author of the paper.
Fire is a natural process that has helped shape this region, but the area has experienced a spike in destructive, high-severity wildfires over the past decade. In fact, three of the five largest wildfires in continental U.S. history occurred in this region in just the past five years. This is due to a combination of climate change and fuel accumulation driven by a century of policies that encouraged fire suppression, curtailed Indigenous cultural burning, and favored harvest of the largest, most fire-tolerant trees, the study notes.
While scientists and resource managers recognize the need for more prescribed fire, its application has not kept pace with the enormity of the challenge. The study said that is because management policies prioritize fire suppression over prevention. There is also a limited fire workforce; regulatory hurdles like permitting, insurance and liability; and few incentives or protections for landowners, tribal members and other people who burn responsibly.
4 key strategies
Researchers identified four key areas where supportive institutional and agency leadership can help expand prescribed fire in the region:
1) Fire culture. After decades of emphasizing wildfire suppression, current fire management culture “does not adequately promote prescribed fire as a management tool,” the study said. Support for prescribed fire along the entire chain of command within agencies is needed to foster a new culture that incentivizes and enables prescribed fire practitioners within and outside of government agencies.
2) Funding. Prescribed fire is considerably more cost-effective than wildfire suppression, which can cost more than $2 billion a year in the U.S., but there is little dedicated funding for prescribed fire projects and lack of flexibility as to when such money can be spent. This impedes fire staffing and limits the kinds of projects that can be done. Year-round, dedicated funding and resources could help increase prescribed fire capacity.
3) Capacity building and cooperation. Connecting agencies with landowners, community members, tribes, prescribed burning associations (PBAs), prescribed fire training exchanges (TREXs) and others can facilitate responsible, effective prescribed fire and cultural burning exchanges. Such groups have limited reach and require investment and support to meet demand.
Inter-organizational agreements can also help local, state and federal agencies share resources and staffing. Formalizing and fully integrating such agreements into fire management plans remains a challenge, the study said. Collaborations that support Indigenous cultural burning are also key.
Partnerships must recognize the unique dimensions of cultural burning, which are inseparable from Indigenous culture. Educating land managers and decision makers about tribal sovereignty and federal American Indian law is critical. Introducing legislation that supports cultural burning can also foster such collaborations.
4) Monitoring and adaptive management. Designated funding and personnel for quantitative monitoring after a prescribed burn can help practitioners better measure success and then apply lessons to future burns.
“All of the barriers identified in the study can be overcome, and they have been at least partially resolved in other parts of the U.S., as well as in other Mediterranean climate regions, such as southwestern Australia,” said co-author Hugh Safford, a research ecologist in the UC Davis Department of Environmental Science and Policy and director of the California Prescribed Fire Monitoring Program. “Fundamental to setting the situation right is developing a culture of safe and regular fire use in California and neighboring states by all landowners and managers, and reducing the officiousness, risk aversion and bureaucracy that hinders access to the tool by the public.”
Additional co-authors include Ashley Grupenhoff and Beth Rose Middleton of UC Davis; Joe Restaino of CAL FIRE; Edward Smith of The Nature Conservancy; Chris Adlam of Oregon State University; and Hiram Rivera-Huerta of Autonomous University of Baja California, Mexico.
This research received financial support from the California Department of Forestry and Fire Protection (CAL FIRE).