🎵 O beautiful, for spacious skies, for amber waves of grain 🎵
Not so fast!
This might be Idaho, one the nation’s top producers of hay, wheat, and barley, but those are not shining seas of beautiful grains. This is cheatgrass.
What is cheatgrass?
Cheatgrass (Bromus tectorum), also known as downy brome, is a fast growing, highly invasive grass species introduced to the United States in the mid 1800s. Originally from Eurasia and the Mediterranean, cheatgrass has spread across the globe, with a particularly high concentration in the Western United States. Cheatgrass thrives in ecosystems with wet winters and dry summers, like the arid Great Basin region spanning portions of Nevada, Utah, Idaho, Wyoming, Oregon and California. It is an annual plant (regrows every year from seeds), and has come to dominate landscapes that traditionally housed a preponderance of perennials (same plant survives for multiple years).
How does cheatgrass spread?
In early spring the green grass is soft to the touch, with delicate clumps of seeds coated in silky threads, dangling from a folded stem. As the season progresses, the plant dries out, shifting to a purple then amber hue. The supple stems transform to wield rigid seeds armed with barb-like awns. The prickly seeds embed themselves in any mode of transportation they can find, easily traveling vast distances by attaching to an animal’s fur or a hiker’s boots.
A single plant can produce thousands of seeds, which remain viable for several years. Seeds also survive passing through the digestive tract, so cattle, deer, and elk that munch on the plants are able to distribute the seeds across active animal habitats. By brute force cheatgrass can outcompete native plants and come to dominate entire landscapes.
Cheatgrass spreads quickly, particularly in areas that have recently been disturbed by wildfire, overgrazing, or perpetual urban construction. A well-documented cycle of overgrazing-cheatgrass-wildfire has led to an explosion of cheatgrass across the Western US. When livestock are permitted to overgraze native vegetation, the exposed soil allows invasive annual grasses to establish a hold. Dried cheatgrass is fantastic kindling, facilitating the spread of wildfires. Once the land is disrupted by wildfire, there is even more open space for cheatgrass to invade and continue the fire cycle. Cheatgrass is currently estimated to cover over 77,000 km2 (~one-fifth) of the Great Basin rangelands and is spreading at 2,300 km2 per year (Smith et al., 2021).
Why is cheatgrass bad?
Reduces biodiversity
Don’t be fooled by those delicate golden stems glistening in the desert sun – this plant is strangling the local native plant competition.
Cheatgrass is so named because it begins growing early in the season and establishes a wide, shallow root system that “cheats” other slower growing plants out of limited water resources. Over several seasons, the cheatgrass entirely outcompetes native plants, establishing a perpetual monoculture.
Much of the Great Basin region, including this area near Boise, Idaho, had historically been a sagebrush steppe. In a land dominated by small bushes and bunch grasses, hundreds of vertebrate species thrived. Now, sagebrush bushes are literal needles in the cheatgrass haystack.
Threatens wildlife habitats
Massive fields singularly of cheatgrass further reduce diversity in the species that depend on the landscape for their home, starting from the ground up. Soil chemistry, structure, and microbiota are altered as lands transition from sagebrush steppe to cheatgrass fields. These changes kickoff a positive feedback loop that makes the habitat increasingly appealing to cheatgrass, and increasingly inhospitable to native plants. Even if cheatgrass is removed, the changes in soil composition make it more difficult for native plants to re-establish themselves.
Insects, birds, and even large mammal populations are also negatively impacted by the spread of cheatgrass. Cheatgrass is pollinated by wind rather than insects. Without tasty flowers, fields of cheatgrass become food deserts for pollinator species. Many birds and small mammals, particularly the greater sage-grouse, depend on sage bush steppes for food, shelter, and breeding. Declines in sage brush steppe habitat due to the wildfire-cheatgrass invasion cycle contribute to declining greater sage-grouse populations. If current trends continue, less than half of the current greater sage-grouse population will remain in 30 years (Coates et al., 2016).
When cheatgrass is still green it can serve as a food source to deer and elk as a spring treat, but upon senescence the grass becomes broadly unpalatable. Because it has already prevented the springtime growth of other native plants, the wasteland of dried cheatgrass leaves only low-quality of forage available for wildlife.
Increases frequency and intensity of wildfires
Cheatgrass dies in early/mid June, creating large networks of densely packed tinder during the driest months of the year in the Great Basin. In undisturbed sagebrush steppes, perennial bunch grasses stay green longer into summer and there are more open spaces between plants to prevent or slow the spread of fire across the landscape. Now, enormous mats of dried cheatgrass quickly wick flames across devastatingly large swathes of land.
Historically, wildfires swept through regions of the West in cycles of roughly every 60-80 years. With the rampant cheatgrass kindling, wildfires ravage the lands roughly every 10 years. With each successive fire, the loss of native species makes way for opportunistic cheatgrass to spread, decreasing the fire-free interval and altering the normal patterns of post-fire plant succession.
How can we prevent the spread of cheatgrass?
Cheatgrass is can be difficult to remove once it is broadly established.
As an annual that grows from seeds each year, the fastest way to eliminate cheatgrass is to remove its ability to create seeds. This can be done by the same techniques that got us into this cheatgrass mess – wildfire and overgrazing. These approaches require careful monitoring and experienced management to ensure the land is repopulated with appropriate local vegetation, without becoming reinfested with cheatgrass or other undesirable invasive plant species.
Selective herbicides, or herbicides applied when cheatgrass sprouts but other native grasses are dormant, is another options to prevent the growth of cheatgrass. Eliminating even a single season of cheatgrass gives native species a chance to re-establish themselves and suppress further cheatgrass expansion. Unfortunately, herbicide resistant cheatgrass strains are emerging, which may limit the effectiveness of this approach in the future (Geddes and Pittman, 2022).
Mechanical/manual intervention to pull out or cut down plants can also tackle cheatgrass invasion. Many parks and preserves have established programs to reclaim lands from cheatgrass by helping establish populations of native plants to compete. While these program may be effective in localized regions they are generally too resource intensive to scale across large geographies.
It’s important to note not all cheatgrass habitats are the same, This is a very versatile species that has adapted to thrive in numerous environments. Cheatgrass is also prominent in hot spots east of the continental divide, such as Colorado. The Front Range of the Rocky Mountains tends to have opposite precipitation patterns of the Great Basin, with drier winters and wetter summers. Technique successful in one region may not be successful in others, so management strategies need to be adapted to each particular region to have the best chances of success.
Regardless where you may encounter cheatgrass, hikers can do their part to help prevent its spread. Check your shoes, socks, and other clothing for embedded cheatgrass seeds before leaving the trail. Remove any cheatgrass seeds and leave them in place to prevent further spread of the invasive grass.
Learn more
Learn more about the difference in cheatgrass management across different ecosystems in this video.
For an in depth review of the history and impact of cheatgrass in the Western US, check out this article.
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Very informative.