Decades of fire suppression in the western United States have created a significant fire deficit, leaving millions of hectares of land vulnerable to larger blazes. New research presented at the AGU 2025 Annual Meeting estimates that 38 million hectares are historically behind on burning, with 74% of the region affected. Scientists urge a shift toward managed fires to restore forest health amid warming and drying conditions.
For over a century, the United States has invested billions in suppressing wildfires to safeguard communities and ecosystems. However, this approach has unintended consequences, as it prevents natural burns that clear dead material and recycle nutrients into the soil. Researchers now warn that much of the western US is in a "fire deficit," where accumulated fuels heighten the risk of catastrophic fires.
The study, led by Winslow Hansen of the Cary Institute of Ecosystem Studies and director of the Western Fire and Forest Resilience Collaborative, was presented on December 18, 2025, at the American Geophysical Union (AGU) Annual Meeting in New Orleans. Using pollen records, soil samples, and the Landfire program, the team reconstructed historical fire patterns and compared them to modern ones. They found that 74% of the western US—spanning nearly 38 million hectares—has burned less than expected based on historical intervals. Closing this gap would require about 3.8 million hectares to burn annually for the next decade, triple the area scorched in the record-breaking 2020 wildfire season.
"Conditions are getting so warm and dry that it's causing huge amounts of fire compared to the historical record," Hansen said. "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."
To address the deficit, experts recommend combining prescribed burns, mechanical thinning of vegetation, and allowing low-risk wildfires to burn naturally. "There are still lots of wildfires that burn today… that are reducing our fuel loads and revitalizing ecosystems," Hansen noted. "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."
Not all areas face the same issue. In the southwest, particularly Southern California, human-ignited fires have created a surplus in shrublands and chaparral, potentially hindering regeneration. Parts of Cascadia also show excess burning, linked to climate-driven drought and heat. "I was a little bit surprised to see these signals of climate change-driven surplus already," Hansen remarked, expecting such trends later.
While the research highlights the need for proactive fire management, the scale of required burning remains daunting, emphasizing the urgency of adapting policies to embrace fire as a restorative force.