WildfiresInvasive Grasses Are Fueling Wildfires Across the U.S.
People alter fire regime patterns by adding ignition sources, such as campfires or sparking power lines; suppressing fires when they develop; and introducing nonnative invasive plants. My research suggests that nonnative invasive grasses may be fueling wildfires across the United States. Some fires are occurring in areas that rarely burn, like the Sonoran Desert and the semiarid shrublands of the Great Basin, which covers most of Nevada and parts of five surrounding states. In the coming months, some of the grasses that help feed these blazes will germinate, producing tinder for future fires.
The Santa Ana winds that help drive fall and winter wildfires in California have died down, providing welcome relief for residents. But other ecological factors contribute to fires in ways that scientists are still discovering.
I study how human actions affect fire regimes – the patterns through which fires occur in a particular place over a specific time period. People alter these patterns by adding ignition sources, such as campfires or sparking power lines; suppressing fires when they develop; and introducing nonnative invasive plants.
My research suggests that nonnative invasive grasses may be fueling wildfires across the United States. Some fires are occurring in areas that rarely burn, like the Sonoran Desert and the semiarid shrublands of the Great Basin, which covers most of Nevada and parts of five surrounding states. In the coming months, some of the grasses that help feed these blazes will germinate, producing tinder for future fires.
In a recent study, I worked with colleagues at the University of Massachusetts and the University of Colorado to investigate how 12 nonnative invasive grass species may be affecting regional fire regimes across the U.S. We found that eight species could be increasing fire in ecosystems across the country.
Altering Historical Fire Patterns
A fire regime is a way to describe fire over space and time or to characterize fire patterns. Understanding fire regimes can help make clear that fire is a natural and integral component of many ecosystems. Knowing historical fire patterns also enables scientists to begin to understand when new or different patterns emerge.
The link between invasive grass and fire is well established. Invasive grasses are novel fuels that can act as kindling in an ecosystem where readily flammable material might not otherwise be present. They can catch a spark that might otherwise have been inconsequential.
For example, in August 2019 the Mercer Fire burned 25 acres in Arizona, scorching native desert plants, including iconic saguaro cacti. A much larger event, the 435,000-acre Martin Fire, destroyed native sagebrush ecosystems in Nevada in July 2018. Invasive grasses helped fuel both fires.
Cheatgrass, which fueled the Martin Fire, is a well-studied invasive grass known to promote fire. But many other invasive grass species have similar potential, and their roles in promoting fire have not been assessed at large scales.
