Western U.S. wildfires have gotten less frequent, though larger (AGU Eos)

Our research study, "Evolving Fire Frequency in the Western United States and Its Links to Human Influence" by Madakumbura et al., was highlighted in science news magazine Eos. An excerpt from the article is below.

Since 1992, wildfires caused by humans have gotten less frequent in densely populated states like California and Arizona but more frequent in more sparsely populated ones like Wyoming, although the total annual burned area in the West has climbed. Credit: Mike Lewelling, U.S. National Park Service

AGU Press Contact: Sean Cummings

Researcher contact: Gavin Madakumbura

WASHINGTON — The number of wildfires burning in the Western United States each year dropped roughly 28% over the past three decades, even as annual burned area and damage from wildfires have soared. A decline in fires accidentally sparked by humans accounts for over 40% of the overall trend, according to a new study.

In areas with few people, fires get more frequent as population density rises. Push past a certain density, however, and fire frequency starts to fall. Understanding how shifting human demographics influence wildfire can help scientists more accurately predict how fire patterns will change going forward.

“It would be premature to talk about informing fire management [based on] these results, but the main implication is that we can incorporate these results into projections of future fire activity,” said Gavin Madakumbura, an atmospheric and oceanic scientist at the University of California, Los Angeles, and lead author of the study.

The study appears in Earth’s Future, AGU’s journal for research on the state of the planet and its inhabitants and their future resilience in the Anthropocene.

More burning, fewer blazes

Wildfire impacts are mounting across much of the Western U.S. The rise in annual burned area from 1992 to 2020 amounts to an increase of about 4% each year. Nine million acres burned in 2020, more than the entire land area of the state of Maryland.

Because of all of this, people often assume the number of fires is increasing, too. But after examining a comprehensive dataset of fire occurrence in the Western U.S. including fire dates, locations, sizes and causes, Madakumbura and his coauthors uncovered a decline from over 25,000 fires per year in 1992 to about 18,000 per year in 2020 — equivalent to 305 fewer fires each year across the 11 continental western states.

Madakumbura said the rise in burned area is due largely to human-driven climate warming, which amplifies the hot, dry conditions that stoke fires to huge sizes. But how often fires start in the first place depends on more than just climate: everyday human activities and fire prevention measures play a role, too.

“We hear people saying the burned area has been increasing, fire damages have been increasing, fire frequency has been increasing. But…fire frequency is more complicated than that,” Madakumbura said. “We wanted to take a stab at that with the best tools we have right now, to see if fire frequency is, in fact, increasing.”

In many parts of the West, the team noted, fires started by humans declined more steeply than those from natural causes like lightning. The trend varied by region, however: human ignitions dropped significantly in California and Arizona, for instance, but rose in Wyoming.

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Read the full article here: https://news.agu.org/press-release/western-u-s-wildfires-have-gotten-less-frequent-though-larger/

Read our research manuscript, Evolving Fire Frequency in the Western United States and Its Links to Human Influence (Madakumbura et al., 2026) here: https://doi.org/10.1029/2025EF007077