In an era where the risk of large, severe wildfires for western forests is rapidly accelerating, new research published this week by researchers at Vibrant Planet, Northern Arizona University, and Blue Forest, published in Frontiers in Forests and Global Change, found that forests that had been thinned were measurably healthier and more resilient than their untreated counterparts. In other words, the research shows that management interventions matter for a forest’s resilience and ability to store durable carbon.
Highlights from the research:
- Thinning reduced high-severity wildfire by 88%.
- Treated forests stabilized carbon stocks within seven years — even through record drought and megafires.
- Larger treatments (>6 hectare, ~15 acres) were especially effective, often acting as fire breaks.
While most forests in the western U.S. are adapted to live and thrive with frequent, low-severity fire, historical fire suppression and intensifying fire and drought patterns are now rewriting the rules—and the risk—for forests and communities. Treated forests—meaning ones whose density was reduced by thinning trees, often followed by understory fuel removal or prescribed burns—retained more live carbon during extreme drought years and burned far less severely when wildfire arrived.
Across the fire-prone Central Sierra Nevada region of California—including portions of the recent Dixie, Caldor, and North Complex megafires—the team found that thinning treatments reduced average wildfire severity by 32% and cut high-severity fire by 88% compared to similar untreated forests.
And the benefits accrued surprisingly quickly: despite an initial “carbon cost” from tree removal, treated forests stabilized live carbon stocks within seven years—even during the record-breaking drought and wildfire seasons of 2020–21. By 2023, carbon levels in treated forests matched or exceeded those in untreated areas.
“Even though the treatments we monitored had a high initial carbon cost in the live trees that were removed, our team saw a dramatic signal of forest resilience emerge in subsequent years,” said Ethan Yackulic, the lead author of the study. “While other studies have shown that management interventions reduce wildfire risk, it was encouraging to witness durable carbon storage at a landscape scale.”
“Most of the western U.S. is contending with an enormous wildfire debt,” said Katharyn Duffy, a study co-author and senior scientist at Vibrant Planet. “It’s not a question of if these forests will burn, but when, and where. Every year, we’re rolling the wildfire dice. Somewhere in the West, the dice always fall.”
The researchers used a natural experiment to test how forest treatments affect wildfire resilience. By comparing ecologically similar forests—some thinned in 2016, others left untouched—they created a real-world “what if” scenario. To ensure accurate comparisons, sites were matched based on vegetation, wildfire hazard, elevation, and other factors, making it possible to isolate the effects of treatment.
“Linking these ‘what-if’ experiments with ongoing monitoring and knowledge of the processes driving effectiveness unlocks essential knowledge for managers,” said Joe Shannon, co-author and lead hydrologist at Vibrant Planet. “Which treatments work best? Do the results change during extreme fire years? What’s the return relative to cost?”
The team found that the benefits of thinning extend beyond fire resistance. Treated forests that avoided fire continued to accumulate carbon even during the severe 2020 drought, while untreated forests stagnated or declined. Follow-up treatments such as prescribed fire or pile burning proved especially effective, both reducing future fire severity and enhancing carbon stability.
“These results help answer one of the central questions facing land managers today: how much treatment, how intensely, and where,” said Sophie Gilbert, contributing scientist. “Part of that answer is committing to a long-term, reciprocal relationship with the land. When we do, forests repay us with resilience—carbon storage, water supply, biodiversity, and cultural values that sustain communities.”
“For fire-prone forests in the West, the cost of doing nothing is just too high now,” added Duffy. “And it’s growing higher each year.”
These findings support a story we have long known, now even more clearly articulated with empirical results; Managed forests can thrive during low-severity wildfire, deliver stronger ecosystem services like carbon storage, and help our communities stay more resilient to damaging megafires. The case for more effectively managing our forests is more clear than ever.
🔍 A deeper dive into the concepts:
What is a “natural experiment”?
Unlike a lab experiment, scientists can’t “control” forests or fires. Instead, they compare real forests that are as similar as possible, except for one difference: treatment. In this study, researchers matched thinned forests with untreated “placebo” forests to isolate the effects of management. This creates a powerful real-world “what if” scenario.
Why do treatments remove trees?
It sounds counterintuitive, but removing some trees reduces competition for water and nutrients, lowers fuel loads, and makes forests less likely to burn at high severity. The short-term carbon cost pays off in long-term resilience.In an era where the risk of large, severe wildfires for western forests is rapidly accelerating, new research published this week suggests that management interventions matter for a forest’s resilience and ability to store durable carbon.
High-severity fire is when flames kill most or all trees in an area. It’s the most destructive kind of fire for forests adapted to frequent low-severity surface fire, and also the hardest for those forests to recover from. Reducing its prevalence in frequent fire ecosystems is key to keeping forests as forests.
Funding information: Award number: 24-CA-11132544-064. This work was partially funded by the American Forest Foundation, as a recipient of an award from the USDA Forest Service #24-CA-11132544-064 Removing Barriers to Scaling the Family Forest Carbon Program and Market Opportunities for Family Forest Landowners.
