A seemingly harmless yet pervasive plant—grass—is playing a major role in the increasing frequency and intensity of wildfires across the United States. With its abundance and flammability, grass has become a significant factor in the spread of fast-moving and destructive fires, particularly under certain weather conditions. Grass fires, while often less intense than forest fires, can spread rapidly and overwhelm firefighting efforts, posing risks to homes and communities, especially those situated close to fire-prone wildlands.
As planet-warming emissions continue to alter climate patterns, wildfires have become more frequent and larger. This has led to a vicious cycle where fires contribute to ecological damage, creating conditions that allow grass to dominate many landscapes. “Name an environment, and there’s a grass that can survive there,” said Adam Mahood, a research ecologist with the U.S. Department of Agriculture. Grass thrives almost everywhere, making it a ubiquitous source of fuel for wildfires.
Over the past three decades, the number of homes destroyed by wildfires in the U.S. has more than doubled. Notably, most of these fires are not traditional forest fires but rather grass and shrub fires. The western U.S. is particularly vulnerable, where two-thirds of homes burned over the last 30 years were affected by grass and shrub fires. The growing risk is partly due to the increased number of homes being built in the so-called wildland-urban interface, where residential areas meet natural landscapes. The amount of land burning in these areas has increased significantly since the 1990s, driven by more construction and human activity, which also raises the likelihood of fires igniting in the first place.
Grass fires can be especially challenging due to their speed. Bill King, a U.S. Forest Service officer managing over 80,000 homes in fire-prone areas, emphasized the need for proactive measures. He stated, “Living on the edge of nature requires an active hand to prevent destruction.” According to King, property owners need to take precautions, as fires can quickly become intense and unpredictable, driven by wind and other factors.
Climate change has exacerbated the situation by creating ideal conditions for grass to flourish and, subsequently, burn. John Abatzoglou, a climate professor at the University of California, Merced, described it as a “perfect storm.” Moderate precipitation encourages grass growth, and warm, dry weather quickly turns it into tinder. Particularly in America’s Plains, grass is more plentiful than in other regions, providing continuous fuel for fires. This phenomenon has been linked to recent megafires like Texas’s Smokehouse Creek Fire and Colorado’s Marshall Fire, which devastated more than 1,000 homes in 2021.
Grass’s flammability is notable because it can dry out rapidly, sometimes within an hour after rain. When combined with invasive shrubs that burn hotter and longer, this creates conditions ripe for disaster. According to fire experts, these “compound extremes” can easily trigger widespread fires, forming what Abatzoglou called “a perfect storm.”
King observed that the nature of wildfires has changed dramatically over his 30-year career. “A big fire was 30,000 acres, and now that’s normal,” he said. “Now, we hear of 1-million-acre forest fires.” Grass has increasingly moved into forest ecosystems, acting like a fuse, linking small, easy-to-ignite fuels to larger trees affected by drought. This connection helps spread more intense fires, leading to greater ecological destruction.
Grass is also rapidly replacing other vegetation, often outcompeting native plants. In the Mojave Desert, for example, invasive red brome grass has fueled massive fires, including recent ones that destroyed vast areas of desert and iconic Joshua Trees. Climate change has further inhibited native plant recovery, leading to more grass dominance and a higher fire risk.
The loss of native ecosystems, such as sagebrush, due to grass invasion has been particularly stark. According to a U.S. Geological Survey study, half of the sagebrush ecosystem, the largest in the continental U.S., has been degraded in the last 20 years. Climate stressors combined with invasive grass species have made the West more vulnerable to wildfires than ever before.
Looking ahead, Mahood warned, “It may seem bad now, but this will probably not seem nearly as bad in the next decade.” As climate patterns continue to change, the risk of more frequent and destructive grass-fueled fires will likely increase, necessitating stronger preventive measures and more effective management strategies.
