Invasive grass is overwhelming U.S. deserts—providing fuel for wildfires

Volunteers are yanking the dangerous grasses from public lands across the American Southwest.

In recent years, large swathes of the desert landscape in the parks around Tucson, Arizona have started to look a lot like grassland. And that’s a problem. 

Buffelgrass, a perennial arid climate-adapted grass from Africa, was brought to the United States in the 1930s and planted throughout Arizona, Texas, and Mexico to control soil erosion and provide cattle forage. In the 1980s, it started to take over the Sonoran Desert—including state and national parks—causing a multitude of ecological issues and fueling wildfires.

In Arizona, the problem is so severe that the grass is officially labeled a noxious weed, but the grass has spread to numerous states from Hawaii to Florida. It shades the ground as it multiplies, which prevents the growth of other species of seedlings.

Buffelgrass “will invade undisturbed desert; it doesn’t require disturbance,” says Kim Franklin, a conservation research scientist at the Arizona-Sonora Desert Museum in Tucson. “It’ll invade Saguaro National Park and Coronado National Forest and it will out-compete the native plants.”

Public lands in southern Arizona preserve the important Sonoran Desert ecosystem and draw hundreds of thousands of people a year for hiking and recreation. Many of those people are locals who have decided to fight back and protect the environment—and their homes.

Volunteers to the rescue

About a dozen volunteers of all ages, from teenager to retiree, came together on a cool winter weekend morning to remove buffelgrass from a small patch of Catalina State Park, a popular, 5,500-acre Tucson park that gets over 200,000 visitors a year. With long, metal pickaxes in hand, the Catalina State Park Buffel Slayers spent the morning hard at work without much chit-chatting. The air was filled not with talking, but the sounds of soft grunts and the thud of pick axes hitting bunches of dry grass.

Gray, gnarled clumps of buffelgrass about a foot high and a foot wide cover the rocky hillside like a scratchy carpet, filling the gaps between granite boulders and crowding the base of towering saguaro cactus and smooth, green palo verde trees. A spray of green tendrils in the center of each plant shows a faint sign of life in a pile of grass that otherwise looks dead.

The buffelgrass has firmly taken hold in this patch of the park. “It doesn’t get any worse than this,” says Joe Ciaramitaro, who has been volunteering to pull grass for 10 years, sometimes multiple days per week now that he’s retired.

Buffelgrass is hard to beat. There are two major lines of defense against this grass: chemical sprays and manual removal. Herbicides are only effective when the plant is green during the summer, which coincides with the hottest days in the desert, so year-round manual buffelgrass pulls have become critical in keeping it out of parks.

Perry Grissom, the restoration ecologist at Saguaro National Park, says that people, like himself, who study invasive species can “see a train wreck before it’s happened, so the hard part is getting other people to see that train wreck.” Luckily, volunteers from the region have stepped up to help. (Visitors are also allowed to sign up for buffelgrass pulls.)

The grass has well-anchored roots that need to be removed to eradicate the plant, so it’s no walk in the park. Volunteers need to wield a crowbar or a pickaxe to get it out completely.

If the plant is gone, the remaining seeds can be viable for years, so even if an area is cleared once, it needs repeat visits. Patty Estes founded the Buffel Slayers volunteer group that works in Catalina State Park, and she says she “doesn’t relax until after three years.”

The Buffel Slayers have been around for five years, but the Sonoran Desert Weed Wackers have been out wrestling with buffelgrass in Tucson Mountain Park since 2000. Kim Franklin says their consistent effort has made a huge difference and kept the issue under control in the park.

The volunteers are passionate. Joe Ciaramitaro, who says he “gets kind of crazy” about pulling grass, volunteers with the Weed Wackers, the Buffel Slayers, and also just on his own. He says there’s one part of Pima Canyon in Tucson that he has weeded solo over the past seven years; it adds up to around 60 acres.

Fuel for the fire

Invasive plants don’t just threaten iconic species by crowding them out—they also can cause them to go up in smoke. Exotic grasses grow between cactus, trees, bushes, and rocks in soil that would normally be devoid of plants. With a thick mat of prime fuel, fire can easily spread after a lightning strike or careless campfire.

“It’s a primary resource threat to the desert part of the park, really, and that’s mainly because of fire,” says Grissom. He says about 90 percent of the invasive species management he deals with is buffelgrass.

Buffelgrass is not the only grass problem around the Southwest, Grissom cautions. Other exotic grasses that were once planted in gardens or for forage, such as lovegrass and red brome, are turning the desert into a tinderbox. These grasses, along with other invasive plants such as stinknet, have provided fuel for some of the largest fires in Arizona in recent years.

In 2020, the state had one of its worst wildfire seasons in a decade, due to massive fires such as the Bush Fire in Tonto National Forest near Phoenix. Grissom says that invasive plants fed the flames of this over 193,000-acre blaze, the fifth largest in state history. This does not bode well for the Southwest: Recent research shows Arizona and New Mexico rank the highest on a vulnerability index for places at high risk of wildfire.

“So the desert historically didn’t burn,” Grissom says. “The best guess is [that] a single spot might burn every 250 years or longer.” Prescribed burns show that fires fueled by buffelgrass burn much hotter and spread faster than typical desert fires.

“Saguaros, palo verdes, they did not evolve with fire. They don’t really have protection from fire,” he says.

The diminishing number of native plants is a major threat to the region’s ecosystem and tourism. Franklin says research shows that although there are fewer young saguaros now, because saguaros can live for over a hundred years, future generations might be the ones noticing the decline.

For some of the volunteers, the motivation is clear: There are still visible scars from last year’s Bighorn Fire, which closed Catalina State Park for a month. Many remember the fear they felt as the 120,000-acre fire threatened their homes nearby.

Beyond burn scars, signs of success are visible, if you know where to look. Estes says some of the areas they’ve cleared out in Catalina State Park have remained free of buffelgrass and are now full of wildflowers in the spring.

While buffelgrass will never be completely eradicated in the Southwest—it likely covers around five million acres in the state of Sonora, Mexico alone—all hope is not lost.

“We can’t eradicate it, but we can control it. Because if we don’t control it, then we lose these amazing saguaro forests,” Franklin says.

Shaena Montanari is an environmental journalist based in Phoenix, Arizona. Follow her on Twitter.

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