Cheatgrass first spread across the U.S. West in the 1800s, carried by settlers and in contaminated seed and straw. The spikey, droopy, almost hairy plant spreads like a weed, chokes out native grasses, and, once dry, lights up like kindling.
It’s now abundant in large swaths of the West, including an estimated one-fifth to one-third of the Great Basin, drylands that reach from Nevada into California, Utah, and parts of Idaho, Oregon and Wyoming. In some places and years, the growth is as dense as carpet, but even in areas where it’s mixed in with native species, the invader has altered fire risk and bred a whole new wildfire cycle. In the last three decades, rangeland area burned has increased by about five times.
Efforts to control cheatgrass and other invasive grasses like it have become the defining missions of scientists at universities, government agencies and land management organizations across the West. But the tools for reducing the proliferation of invasive plants have been limited—they can be torn out, seeded out with native plants or treated with herbicides, but each method has drawbacks and constraints. Now scientists and researchers are advancing another low-tech option to deal with cheatgrass: targeted cattle grazing.
New research out this spring showed strategically grazing cattle in the fall—when the plant is little more than a husk ready to ignite—could reduce cheatgrass abundance by more than half and create important gaps in fields of grassy fuel to keep wildfire from jumping to new plants and spreading. The results, from researchers at the University of Nebraska – Lincoln, the University of Nevada – Reno and the U.S. Department of Agriculture, are part of a growing body of research examining how grazing practices may help manage Western lands reshaped by humans.
When cheatgrass becomes dominant in an area it can more than double fire risk. The “bunch grasses” and shrubs that are native to the West can slow the spread of wildfires, as flames in one clump of grass cannot easily reach other bunches that are widely spread out across otherwise bare soil. But cheatgrass grows in what firefighters call a “continuous fuel bed,” as dense with grass as a field of wheat, which allows fire to spread easily.
“We can’t control all the fires, but we can change those fuel characteristics in a way that gives us a chance,” said Barry Perryman, one of the study’s authors and the chair of the Department of Agriculture, Veterinary, and Rangeland Sciences at University of Nevada – Reno.
Perryman and his colleagues placed liquid protein supplements—a mix of protein and molasses stored in huge tanks—throughout a Nevada pasture heavily invaded by cheatgrass in order to lure cows to graze in certain areas, some of them miles from water. On flat land, the cattle were able to eat up enough cheatgrass to create a fuel break, an area where vegetation is removed to keep fire from crossing it. The grazers reduced cheatgrass by an average of more than 60 percent.
But how the results may be applied will vary by location, because the ecological conditions that shape the spread of cheatgrass are complex, as is the land management needed to confront it. Precipitation levels, topography, fire recurrence, grazing frequency and the proportion of native vegetation all contribute to the prevalence of cheatgrass and whether grazing is an effective tool for controlling it.
Cheatgrass can set down roots in fall or spring and it germinates early, shooting out of the soil early enough to beat many perennial grasses for resources. It releases its seeds and cures into fuel for wildfires early, too. After a burn, those seeds sprout quickly, beating out native species and allowing it to spread further.
“It’s just highly competitive,” said Jeanne Chambers, a senior scientist emeritus at the U.S. Forest Service Rocky Mountain Research Station. “Once it begins growing in a favorable environment, it can grow very rapidly, and it can mature high numbers of seeds.”
The plant turns to straw in mid-summer. Areas that may have avoided fire in the past now have a pile of flammable material scattered across the landscape. And climate change is helping its rise. Cheatgrass is quicker to establish after fires burn through an area. Warmer temperatures and changing precipitation are helping it move to higher elevations, though such changes are also making it harder for it to grow in some other areas. Researchers estimate annual grasses like cheatgrass have spread over eight times more land in the Great Basin since 1990.
And when cheatgrass has taken over an area, it can spark relatively easily, even when hot, dry and windy “fire weather,” is relatively mild, Chambers said. That’s pushed parts of the Great Basin into a fire cycle that spins much more quickly than it did in the past. The “wildfire crisis” has fostered more collaboration between federal and state agencies to confront the problem, said Chambers, leading to projects like the one involving Perryman and the USDA.
Setting cattle and other types of livestock on cheatgrass-heavy land is a win-win, said Mark Lacey, a rancher who owns Lacey Livestock and grazes cattle in parts of California that overlap with the Great Basin. Ranchers need grazing land, and cows chewing down grass provides a cheap tool for state and local governments strapped for firefighting resources. The practice also supports ranchers, who help drive the economy, produce food and create jobs in many rural places, he said.
“The great thing about using grazing, at least from the cattle standpoint, is that most cattlemen are happy to go graze and we’re happy to do it for free. So, there’s very low cost or no cost to the state of California and the taxpayers,” said Lacey, who previously served as president for the California Cattlemen’s Association. “We get to do what we naturally need to do and the state gets that service.”
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Lacey said his region of California hasn’t seen the same type of huge grassland burns as other parts of the Great Basin, which means that cheatgrass doesn’t have as strong of a foothold. But the grass thrives on disturbance, so as fires become more severe due to climate change it will continue encroaching into new areas.
“It’s a prolific invasive—it spreads easily,” said Lacey. “If we start burning a lot of these sagebrush uplands, … there’s no doubt cheatgrass will come.”
Leaving the land to total cheatgrass domination is not an option. In part, due to fires, but also because many species rely on the habitats they invade. For Lacey, protecting the habitat of the greater sage grouse, which has been considered for listing under the Endangered Species Act, is essential. If the bird’s population suffers, the government may put new protections on the land, including restrictions on where and when he can graze his cattle.
Ecologists’ understanding of the environmental interactions that control cheatgrass are developing in real-time. Chambers, who was not involved in the study, would like to see off-season grazing experimented with in more locations, in more plant communities and under more environmental conditions to understand its varied effects.
“It is not a one-size fits all,” she said. “We need to be able to tailor it to the specific conditions that we have in a given location.”
Jutta Burger, science program director at the California Invasive Plant Council, said grazing needs to be calibrated to the environment to ensure it has its intended effect. Munching livestock can reduce fine fuels and fire risk, she said, but needs to be accompanied by other management like seeding to restore native vegetation.
“Just because something reduces fuels doesn’t necessarily mean it’s going to be improving the native perennial grassland habitat,” she said. “There’s definitely a role [for grazing], … it’s just there is no silver bullet.”
Dealing with cheatgrass as well as other invasive grasses will require critical thinking about timing, duration and intensity of the practice, said Perryman, but it will also require more flexibility for grazing. Permits issued by federal agencies to grazers, for instance, are organized in part around keeping perennial grasses healthy and making sure cattle don’t eat too many of them. But cheatgrass has altered those environments, and Perryman said how the invasive grass is managed should be at least as important as the concern over native perennials.
“It’s all the same package,” said Perryman. “You can’t deal with one without dealing with the other.”