Invasive annual grasses (iags)
Cheatgrass, ventenata, and medusahead rye are invasive annual grasses (IAGs) present in Wyoming. These non-native grasses vary in their distribution across the state. Medusahead is rare, ventenata is mostly isolated to northeastern Wyoming, and cheatgrass is widespread, occurring in every Wyoming county.
What’s at Stake & What Do We Stand to Lose?
If we fail to act—or if funding is not sustained—the consequences are significant. An estimated 49.4 million acres of Wyoming are suitable habitat for invasive annual grasses.
A recent economic study by the University of Wyoming found:
$33
Million
In current annual economic losses from reduced grazing due to IAGs
Up to
43%
Of the value of Wyoming’s agricultural lands at risk if no action is taken
$139
Million
In potential losses across suitable habitat
Choke out cheatgrass before it chokes out Wyoming.
Invasive species spread when funding stops.
Cheatgrass currently impacts an estimated 5.3 million acres in Wyoming, and that number continues to grow. An additional 10 million acres are estimated to have cheatgrass present at low levels. Today, 21 of 23 counties list cheatgrass as a county-declared noxious weed. Although cheatgrass is not included on the state-designated noxious weed list, there is broad agreement that it poses a severe and growing threat to Wyoming’s landscapes.
Why Invasive Annual Grasses Matter
Wyoming must actively fight invasive annual grasses. The Wyoming Weed and Pest Council, with support from partners across the state, is leading this effort. Proactive management is essential to limit the spread and protect Wyoming’s lands.
As invasive annual grasses establish, they displace desirable native vegetation, reducing forage for livestock and wildlife. When these grasses dry out, they become fine fuels dramatically increasing wildfire frequency, intensity, and spread. By preventing invasion and reducing wildfire risk, we can protect core sagebrush rangelands that support agriculture, wildlife habitat (including mule deer, pronghorn antelope, and sage grouse), recreation, and the long-term health of Wyoming’s ecosystems and economy.
Rehabilitation saves Wyoming Landscapes
Before
After
Credit Fremont County, Wyoming
Investing in Solutions
Following the record-breaking 2024 wildfire season, Wyoming’s governor and legislature recognized the urgent need for funding to support invasive grass management related to wildfire impacts. These funds have supported treatment, prevention, and restoration projects focused on invasive annual grasses and sagebrush rangelands.
The Wyoming Wildlife and Natural Resource Trust Fund has distributed millions of dollars to advance these efforts statewide. Projects like these are critical to protecting Wyoming’s landscapes for future generations. However, additional funding and landowner participation remain essential to proactively control invasive grasses, maintain rangeland productivity, protect wildlife habitat, and reduce hazardous fuels that intensify wildfires.
Learn More
- NE Wyoming’s House Draw Fire Overview of post-fire response and invasive grass management efforts following the House Draw Fire.
- Wyoming Wildlife & Natural Resource Trust Fund Projects Interactive map showcasing WWNRT-funded projects, including invasive annual grass and wildfire-related efforts.
- Defend Your Core: An Invasive Annual Grasses Story A video from the University of Wyoming’s IMAGINE program highlighting western efforts to protect sagebrush core areas.
- Sublette County Cheatgrass Program Video highlighting Sublette County Weed and Pest’s approach to managing cheatgrass.
- NRCS: Sublette County Invasive Grass Project Article describing collaborative conservation efforts in Sublette County.
- Wyoming’s Fight Against Cheatgrass An in-depth look at Wyoming’s response to cheatgrass as a major threat to western ecosystems.
- UW IMAGINE Program Research, tools, and outreach focused on invasive annual grasses in natural ecosystems.
- Invasive Annual Grass Management Toolkit A practical guide for managing invasive annual grasses across the western United States.