Forest fires may get more attention, but a new study reveals that grassland fires are more widespread and destructive across the United States. Almost every year since 1990, the study found, grass and shrub fires burned more land than forest fires did, and they destroyed more homes, too.
But many residents are not as aware of wildfire risk in grasslands and shrublands.
When the Marshall fire swept into the Boulder suburbs in 2021, killing two people and incinerating more than 1,000 homes, many residents were shocked that such a fierce blaze could encroach on their community, far from the forests of the Rocky Mountains.
The community’s risk was actually high: Many homes were close to wide expanses of tall, dry grass that were primed to burn. When a grass fire sparked, strong winter winds propelled it toward nearby neighborhoods where the flames easily jumped from grasses to homes, sometimes using the wooden fencing that separated human and natural landscapes as a springboard.
One resident affected by the fire told investigators it was “a wake-up call” to the risks of grassland fires.
Volker Radeloff, a professor of forest ecology at the University of Wisconsin-Madison, who led the new study, pointed to both the Marshall fire and the recent Lahaina fire in Hawaii as two extreme examples of the risks wildfire can pose outside of forests. Both started with burning grasses and grew into devastating urban infernos.
Wildfire risk to homes is especially high in areas where the built environment meets wild vegetation, Dr. Radeloff said, a region called “the wildland-urban interface,” or WUI, for short (pronounced WOO-ee).
Wildfire risk increased across the United States in recent decades, the new study found, but was highest in WUI areas. These include places like the Boulder suburbs, where neighborhoods abut wild vegetation, as well as areas where individual homes are surrounded by wilderness.