Forest fires can devastate vast swaths of land, but in the United States, another category of conflagrations takes the title of most destructive.
Of the homes destroyed in wildfires across the contiguous United States from 1990 to 2020, 64 percent — nearly 11,000 — were razed by grassland and shrubland fires, researchers report in the Nov. 10 Science.
“We often think about forest fires because that’s what we see on the news … they’re dramatic, they’re huge, they’re intense,” says ecologist Volker Radeloff of the University of Wisconsin-Madison, “but grassland and shrubland fires can also be quite destructive.” For instance, the 2023 Lahaina fire on the Hawaiian island of Maui, fueled by invasive wild grasses, killed at least 98 people and destroyed some 2,200 buildings.
For the new study, Radeloff and his colleagues analyzed three decades of data on wildfire occurrence, land use and housing, hoping to learn more about what factors fuel such destructive blazes.
The team found that about 337,000 square kilometers of grasslands and shrublands burned from 1990 to 2020, compared with about 144,000 square kilometers burned by forest fires. Though forest fires were about twice as likely as grassland fires to burn down homes they encountered, the much larger expanse burned by grassland and shrubland fires helped make them more destructive overall.
The data also revealed that U.S. wildfire risk had risen substantially. Today, roughly 148,000 houses stand in areas where wildfires have burned before — that’s more than twice as many as in 1990. About half of those additional homes were built on land that had already burned prior to 1990, the team found, while the rest were already standing when a blaze burned through.
Radeloff hopes more people will consider their wildfire risk and take steps to prepare, be that planning evacuation routes or fireproofing their homes. Evading wildfire danger, it seems, takes more than getting out of the woods.
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