Invasive annual grasses are a losing proposition for ranchers. Weeds like cheatgrass, medusahead and ventenata diminish the value of grazing land by replacing nutritious native plants with subpar forage. They also double the risk of wildfire.
“Five years ago, dry cheatgrass fueled the intensity of a fire that devastated our range. It took grazing out of the equation on public allotments for over two years,” says Brenda Richards, who runs cattle in the Owyhee region of southwestern Idaho with her husband and three grown sons.
The Soda Fire near her ranch scorched 280,000 acres of rangeland in Idaho and Oregon. Richards and dozens of her neighbors lost livestock as well as forage, taking a big financial hit.
Cheatgrass is one of the biggest invasive species problems in the Western U.S. It was brought to North America by European settlers in the mid-1800s. Cheatgrass is now found in all 50 states, but it’s spreading most rapidly in the West, where summers are hot and dry. More than 50 million acres of grazing lands are estimated to have more than 15% cover of cheatgrass.
Biology of cheatgrass
This invasive annual grows in the spring and then dies between late April and June. That’s why it’s called cheatgrass; it turns brown when livestock need green grass, cheating ranchers of nutritious forage in the summer and fall.
In addition, cheatgrass crowds out native perennial grasses that better sustain livestock year-round. Because it has shallow roots, cheatgrass absorbs more of the water and nutrients during the spring, outcompeting native plants for limited resources.
Cheatgrass also disrupts important ecological cycles. The roots of native bunchgrasses and shrubs grow up to 8 feet deep, helping to cycle nutrients, retain water and reduce erosion. Soil health suffers when deep-rooted natives are replaced by shallow-rooted invasive grasses.
Even more worrisome, invasive annual grasses cause more frequent fires. In places where cheatgrass has taken over, fires occur every three to five years, as opposed to the historic average of 50 to 100 years. Since cheatgrass dries out earlier than native vegetation, the fire season is also longer than it used to be.
Plus, these weeds are generating larger, more intense wildfires. Cheatgrass has very fine leaves and stems, and it ignites as easily as tissue paper. The plants also grow close together, forming a continuous fuel base that causes fire to spread rapidly.
After a fire, cheatgrass becomes even more dominant. Unlike native plants, cheatgrass is able to use the increased nitrogen in the soil after a fire efficiently, and it quickly invades the empty spaces created by a burn. This creates a vicious cycle.
While the scale of the problem can seem overwhelming, proactive efforts are underway to protect rangelands from the spread of invasive annual grasses. For instance, rancher Brenda Richards — who is also the coordinator for the Idaho Rangeland Conservation Partnership — volunteered to help develop Idaho’s new “Cheatgrass Challenge." This collaborative approach provides cost-share funds for ranchers through the USDA Natural Resources Conservation Service Environmental Quality Incentives Program to treat weeds across land ownership boundaries, where infestations are still low.
One treatment option is to apply herbicide and then promptly reseed with native perennial plants. Another is to target livestock grazing in cheatgrass-dominated areas in the spring to reduce available fuels before the start of the fire season. Fostering diverse, healthy native plant communities is the most effective prevention strategy, and it saves ranchers money in the long term.
Taking a cue from Idaho’s model, the Western Governors’ Association recently released a “Cheatgrass Toolkit” to help landowners combat this threat to grazing lands. The toolkit provides a flexible road map and science-based tools for producers and partners to manage invasive annual grasses voluntarily. It includes an up-to-date, free online map that uses remote imagery to show where invasive grasses are located, and where they are increasing.
Visit rangelands.app/cheatgrass to see how your region or ranch is faring.
Randall writes from Missoula, Mont.