CNN
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A ubiquitous, resilient, and seemingly harmless plant is fueling an increase in large, fast-moving, and destructive wildfires in the United States.
Grass is as plentiful as sunlight, and under the right weather conditions, it's like gasoline for wildfires. All you need is a spark to explode.
Global warming emissions are wreaking havoc on temperatures and precipitation, resulting in large and frequent fires. These fires are accelerating a vicious cycle of ecosystem destruction and helping grass become king.
“You name an environment, and there are grasses that can survive in it,” says Adam Mahood, a research ecologist with the U.S. Department of Agriculture's Research Service. “There's going to be some grass growing in that 10-foot area that's not paved.”
Grass fires are typically less intense and shorter-lived than forest fires, but they spread explosively, exceeding firefighting resources and burning down increasing numbers of homes built near fire-prone wildlands. That's possible, a fire expert told CNN.
Over the past 30 years, fires have become even bigger and the number of U.S. homes destroyed by wildfires has more than doubled, a recent study found. Most of those homes were not burned by forest fires, but by fire moving through grass and shrubs.
The study found that the West is most at risk, with more than two-thirds of homes burned in the past 30 years located in the West. Nearly 80% of it was destroyed by grass and brush fires.
Helen H. Richardson/Director of Media News/The Denver Post/Getty Images
Christmas lights decorate homes as the Marshall Fire rages in Louisville, Colorado, on December 30, 2021.
One part of the equation is that the so-called wildland-urban interface is moving people closer to fire-prone wildlands. The amount of land burned in this sensitive region has increased rapidly since the 1990s. The same goes for the number of houses. According to the study, there were approximately 44 million homes on the border as of 2020, an increase of 46% over the past 30 years.
There are obvious risks to building in flammable areas, but humans are also responsible for starting most fires, making them more likely to start in the first place.
Bill King manages more than 80,000 homes in the sparsely populated areas of Kansas and Colorado that straddle the border between wilderness and city. U.S. Forest Service officials said living on the edge of nature requires active hands to prevent destruction.
“Property owners must do their part too, because these fires are so large and intense and sometimes caused by wind that even if there is a major fuel break, nothing Because you can find miles ahead,” King said.
Climate-induced fires are ravaging the western half of the United States on all sides.
“Globally, the places with the most fires are places with moderate precipitation,” said John Abatzoglou, a climatology professor at the University of California, Merced. “It's a bit like Goldilocks: not too wet, not too dry, just right, and has enough ignition.”
In America's grassy heartland, typically dry and often windy plains, a series of seasonal climate extremes conspire to create ideal fire fuel conditions for perennial grasses. Grass is more plentiful here than in other parts of the United States, providing a continuous supply of fuel for fires.
The region is prone to large fires like the Smokehouse Creek Fire, the largest fire in Texas, and more destructive fires like the Marshall Fire in Colorado, which destroyed more than 1,000 homes in 2021. ing.
When it rains, more grass grows. They then go dormant or play dead in the winter. King Lindley and Todd Lindley, fire meteorologists with the National Weather Service in Norman, Oklahoma, said winters were warm and snow-free, and grasses were warm and dry in late winter and early spring, especially on the northern plains. It is said that it will be exposed to.
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The charred remains of a vehicle sit behind a store that was destroyed by the Smokehouse Creek Fire as it moved through the Texas Panhandle on March 2, 2024.
Lindley said grass is uniquely flammable because it is sensitive to weather. Unlike forests, it doesn't take long periods of warm, dry weather for grass to ignite. After rain, moisture is lost from the plant in just an hour, and sometimes within a day. Throw in sparks, strong winds, and invasive shrubs, and they'll burn hotter and longer, creating a grass fire disaster.
“If we can get these compound extremes, sequences of extremes one after the other, the right sequence, then we have the potential to deal with these types of wildfires,” Abatzoglou said. “You're basically creating the perfect storm for the fire to spread.”
Extreme drought and years of forest neglect are causing larger and more intense fires in western forests, King said.
“When I started fires 30 years ago, large fires were 30,000 acres, and now that's normal and typical,” King said. “There's probably one fire of that size a year, one every few years. And now he hears about a million-acre forest fire.”
Grass is also present in forest systems, acting like a fuse that connects ignitable fine fuels to larger drought-affected tree systems, allowing more intense fires to start and spread.
When the trees die, the grass moves. Grass recovers from fire much faster than other plants and can sometimes ignite again within a few months. Dr. King saw this firsthand.
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A burnt car and house are seen in an area destroyed by a wildfire in Lahaina, Hawaii, on August 18, 2023. The fire quickly spread through the encroaching grass.
“A landscape with burnt grass could have green grass growing within a day or two. That's how quickly forests rejuvenate,” King said. “Forests may take years or generations to recover, or they may never recover in our lifetime or in our generation.”
As more plants burn across the West, they are being replaced by both native and exotic grasses.
In the desert, fires are burning in places where they weren't before, said Mahood of the Agriculture Department. The same drought-induced fires are magnified in deserts because annual grasses, unlike perennials on the plains, are absent year-round.
These grasses take advantage of rare rains to reproduce and then die, forming a carpet of fire fuel on the desert floor.
Two recent fires in California's Mojave National Preserve are a good example, Mahood said. These fires exploited the invasive red bromegrass and burned hundreds of thousands of acres of the Mojave Desert and more than a million iconic Joshua trees.
Increased hot and dry conditions inhibit native plant recovery. As a result, grass grows.
The West's stocky, iconic sagebrush is the single largest ecosystem in the Lower 48, but half of it has been lost or degraded in the past 20 years. A USGS study found that an area of sagebrush roughly the size of Delaware falls victim to grass, fire, and other stressors each year.
Increased grass growth and a complex interplay of climate stressors further increase the risk of fire now and in the future.
“It may look bad now, but it probably won't look that bad over the next 10 years,” Mahood said. “Think about how bad the fire season was 20 years ago. Now that seems like nothing.”
