The western U.S. Tried to stop wildfires and it backfired
Wildfires are not always purely destructive. In many forests, fire can clear out built up dead material, return nutrients
Wildfires are not always purely destructive. In many forests, fire can clear out built up dead material, return nutrients to the soil, and help ecosystems reset. For more than 100 years, the United States has spent billions of dollars on fire suppression to protect people, homes, and sensitive environments. But putting out too many fires can also prevent landscapes from getting the burns they need, allowing extra fuel to accumulate and raising the risk of larger fires later.
New research to be presented at AGU’s 2025 Annual Meeting in New Orleans reports that nearly 38 million hectares of land in the western United States are historically behind on burning. The researchers describe these areas as being in a “fire deficit.” This estimate was revised from 59 million hectares in the abstract to a final total of 38 million hectares.
“Conditions are getting so warm and dry that it’s causing huge amounts of fire compared to the historical record,” said Winslow Hansen, director of the Western Fire and Forest Resilience Collaborative and scientist at Cary Institute of Ecosystem Studies. “However, we still are dealing with the legacy of 150 years of fire suppression. Together, drying conditions and overly dense fuels portend a challenging and more fiery future.”
Hansen will present the findings on December 18 at AGU25, joining more than 20,000 scientists discussing the latest Earth and space science research.
How scientists mapped fire deficit and fire surplus
To determine where fire is missing and where it is happening too often, the team used geospatial evidence such as pollen records and dirt samples. From that information, they estimated historical fire return intervals, which were then reconstructed through the Landfire program.
When the team compared modern annual burn patterns with the historical record revealed by the data, they found that 74% of the western U.S. is currently in a fire deficit. To close that gap, forests would need about 3.8 million hectares to burn each year for a decade. That annual amount is three times the forest area that burned in 2020, which remains the record year for wildfire burn area in the U.S.
Strategies to reduce wildfire risk and restore healthier fire cycles
The scale of that burning is intimidating, but Hansen and his colleagues say there are several ways to make progress. They point to a mix of prescribed burns, mechanical thinning, and the use of managed wildfire to reduce the deficit.
“There are still lots of wildfires that burn today… that are reducing our fuel loads and revitalizing ecosystems,” said Hansen. “Instead of suppressing those fires and putting them out, we’ve got to let them do good ecological work to help us tackle this challenge when risk is low.”
Some regions have the opposite problem too much fire
Even as much of the West is overdue for fire, the southwest is dealing with the reverse situation. Human started wildfires have pushed shrublands and chapparal ecosystems into a fire surplus, especially in Southern California.
“You’re getting more fire than you would have historically, which can even threaten resilience,” Hansen said. “These shrubland ecosystems might not be able to regenerate if the fire is too frequent.”
Parts of Cascadia are also showing a fire surplus, which the researchers link to climate change driving higher temperatures and more drought, conditions that can set the stage for blazes.
“I was a little bit surprised to see these signals of climate change-driven surplus already,” said Hansen. “I’d expected that would be something we would see in the next decade or two instead.”
Abstract information
B42C-08 Erasing the western US forest-fire deficit will require approximately 60 million hectares of ecologically beneficial burning over the next decade.
Thursday, December 18, 11:45 — 11:55 Central Time
Room 265-266 NOLA Convention Center
