In the western United States, researchers envision a four-legged tool to fight two enemies: wildfires and cheat weed


Cheatgrass first spread in the western United States in the 1800s, carried by settlers and in contaminated seed and straw. The spiky, drooping, almost hairy plant spreads like a weed, chokes out native grasses and, when dry, lights up like kindling.

It is now abundant in large areas of the West, including about one-fifth to one-third of the Great Basin, arid lands that stretch from Nevada to California, Utah and parts of Idaho, from Oregon and Wyoming. In some places and in some years, the growth is as dense as a carpet, but even in areas where it is mixed with native species, the invader has altered the fire danger and spawned a whole new cycle of wildfires. forest. Over the past three decades, the area of ​​rangeland burnt has increased about fivefold.

Efforts to control cheat weed and other invasive weeds like it have become the defining missions of scientists in universities, government agencies, and land management organizations across the West. But the tools to reduce the proliferation of invasive plants are limited: they can be uprooted, sown with native plants or treated with herbicides, but each method has its drawbacks and constraints. Today, scientists and researchers are offering another low-tech option to combat cheat grass: targeted livestock grazing.

New research this spring has shown that strategic livestock grazing in the fall – when the plant is little more than a husk ready to ignite – could more than halve grass abundance in cheat and create large gaps in the grassy fuel fields to prevent the wildfire from spreading. plants and propagation. The findings, from researchers at the University of Nebraska – Lincoln, University of Nevada – Reno and the U.S. Department of Agriculture, are part of a growing body of research examining how grazing practices can help manage the western lands remodeled by man.

When cheat grass becomes dominant in an area, it can more than double the risk of fire. “Clump grasses” and shrubs native to the West can slow the spread of wildfires because the flames in a clump of grass cannot easily reach other widely scattered clusters on otherwise bare ground. But cheat grass grows in what firefighters call a “continuous fuel bed,” as dense with grass as a field of wheat, allowing fire to spread easily.

“We can’t control every fire, 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 chairman of the Department of agriculture, veterinary sciences and rangelands. at the University of Nevada – Reno.

Perryman and his colleagues placed liquid protein supplements – a mixture of protein and molasses stored in huge reservoirs – in a Nevada pasture heavily overgrown with cheatgrass to entice cows to graze in certain areas, some miles from the water. On flat ground, cattle may have eaten enough cheat grass to create a fuel cut, an area where vegetation is cleared to prevent fire from passing through it. Grazers reduced cheatgrass by over 60% on average.

But how the results can be applied will vary by location, as the ecological conditions that shape the spread of cheat grass are complex, as is the land management needed to deal with it. Rainfall levels, topography, fire recurrence, grazing frequency, and the proportion of native vegetation all contribute to the prevalence of cheatgrass and the effectiveness of grazing in controlling it.

Cheatgrass can root in fall or spring and it sprouts early, springing out of the ground early enough to beat many perennial grasses for resources. It also releases its seeds and turns into fuel for forest fires early. After a burn, these seeds germinate quickly, defeating native species and allowing them to spread further.

“It’s just very competitive,” said Jeanne Chambers, senior scientist emeritus at the US Forest Service’s Rocky Mountain Research Station. “Once it starts growing in a favorable environment, it can grow very quickly and it can ripen a lot of seeds.”

The plant turns to straw in mid-summer. Areas that could have avoided fires in the past now have piles of flammable materials scattered across the landscape. And climate change is contributing to its growth. Cheatgrass establishes faster after fires move through an area. Warmer temperatures and changing rainfall help it move to higher elevations, although these changes also make it more difficult for it to grow in other areas. Researchers estimate that annual grasses like cheater have spread to eight times as much land in the Great Basin since 1990.

And when cheatgrass has taken over an area, it can trigger relatively easily, even when the hot, dry and windy “fire weather” is relatively mild, Chambers said. This has pushed parts of the Great Basin into a fire cycle that spins much faster than in the past. The “wildfire crisis” has fostered greater collaboration between federal and state agencies to deal with the problem, Chambers said, leading to projects like the one involving Perryman and the USDA.

Putting cattle and other types of livestock on land rich in cheatergrass is a win-win situation, said Mark Lacey, a rancher who owns Lacey Livestock and grazes cattle in parts of California that straddle the Greater Bowl. Ranchers need pasture, and grass-chewing cows are a cheap tool for resource-strapped state and local governments to fight fires. The practice also supports pastoralists, who help boost the economy, produce food and create jobs in many rural areas, he said.

“The advantage of using grazing, at least from a livestock perspective, is that most herders are happy to go out to graze and we are happy to do so for free. So there’s very little or no cost to the state of California and the taxpayers,” said Lacey, who previously served as president of the California Cattlemen’s Association. “We can do what we naturally have to do and the state gets that service.”

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Lacey said his area of ​​California hasn’t seen the same kind of massive grassland burns as other parts of the Great Basin, which means cheat grass doesn’t have as strong a hold. But the grass thrives on disturbance, so as the fires grow more severe due to climate change, it will continue to encroach on new areas.

“It’s a prolific invasive – it spreads easily,” Lacey said. “If we start burning a lot of these sagebrush uplands, … there’s no doubt that the cheat weed will come.”

Leaving the land to total cheatgrass dominance is not an option. Partly because of the fires, but also because many species depend 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 can put new protections on the land, including restrictions on where and when it can graze its livestock.

Ecologists’ understanding of the environmental interactions that control cheat grass is growing in real time. Chambers, who was not involved in the study, would like to see off-season grazing experimented with in more places, in more plant communities and under more environmental conditions to understand its varied effects.

“It’s not one size fits all,” she said. “We have to be able to adapt it to the specific conditions we have in a given place.”

Jutta Burger, science program director at the California Invasive Plant Council, said grazing must be calibrated to the environment to ensure it has the intended effect. Livestock nibbling can reduce fine fuels and fire risk, she said, but must be accompanied by other management like seeding to restore native vegetation.

“Just because something reduces fuels doesn’t necessarily mean it’s going to improve native perennial grassland habitat,” she said. “There is definitely a role [for grazing]…it’s just that there is no silver bullet.

Dealing with cheatgrass as well as other invasive weeds will require critical thinking about the timing, duration and intensity of practice, Perryman said, but it will also require more flexibility for grazing. Permits issued by federal agencies to grazers, for example, are organized in part to maintain the health of perennial grasses and ensure that livestock do not eat too many of them. But cheatgrass has altered those environments, and Perryman said how invasive grass is managed should be at least as important as concern for native perennials.

“It’s the same package,” Perryman said. “You can’t take care of one without taking care of the other.”


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