High-Severity Wildfires Burn 30 Times More Area Than In 1985, UCLA Study Finds

LOS ANGELES, CA — High-severity wildfires that kill large numbers of trees are now burning far more acreage in California than they did four decades ago, according to a UCLA study published Monday.

The study, appearing in the journal Proceedings of the National Academy of Sciences, found that the area burned by high-severity fires in California increased thirtyfold between 1985 and 2024, while overall forest acreage burned annually increased tenfold.

Researchers said severe fires, which often kill entire stands of trees rather than allowing forests to recover naturally, have overtaken lower- severity fires as the dominant type of forest fire in California.

"These high-severity, forest-replacing fires used to be uncommon, and now it's the dominant fire type," senior author Park Williams, a UCLA professor of geography, said in a statement. "Fire is a natural process that can be healthy for ecosystems, but most of California's tree species have a difficult time coming back following fires that kill huge swaths of trees."

According to the study, high-severity fires have outnumbered low- severity fires every year since 2012.

Researchers linked the trend to increasingly warm and dry conditions associated with climate change, as well as decades of fire suppression that have allowed dense vegetation and underbrush to accumulate in many forests.

"When the weather is hot and dry, the vapor-pressure deficit is high, which leads the atmosphere to act like a sponge, soaking up surface water," said lead author Mitchell Hung, a doctoral student at Stanford University who conducted the research while at UCLA. "In general, the warmer and drier the atmosphere, the more high-severity fire we saw over the last 40 years."

The study found that the increase in severe fires has been greatest in densely forested areas with high levels of biomass and combustible vegetation.

Researchers warned that repeated high-severity fires could permanently alter California's landscapes by preventing forests from regenerating and encouraging the spread of grasslands and shrublands in formerly forested areas.

The loss of forests could also affect air quality, water management, tourism and other sectors of the state's economy, according to the study.

Researchers said forest-thinning projects and prescribed burns could help reduce the risk of severe fires in some areas, although broader climate trends remain a major driver of wildfire behavior.

City News Service