In science fiction, the silent-invasion plot is well worn.
An alien species slowly takes over its target land, stealthily replacing the native population until the invasion is complete. In the movies, a plucky band of scientists and citizens grow wise to the threat and fight back, but it’s often too late.
It’s not science fiction when it’s actually happening, as it is in the Western United States. The invaders there are invasive annual grasses like cheatgrass, medusahead and ventenata.
These non-native plants (which might be better called insidious annual grasses) have silently spread throughout the West and now cover millions of acres. They crowd out native perennial grasses and other native vegetation, increase wildfire intensity and risk and reduce rangeland’s productivity and value because they are unpalatable to cattle.
But, like in the movies, there are plucky scientists and citizens fighting back, perhaps nowhere more so than Wyoming, which has made invasive grass management a priority.
“Wyoming formed a cheatgrass task force in 2005, and in 2016 found ventenata and medusahead in Sheridan County,” said Jaycie Arndt, an assistant research scientist for the University of Wyoming. “It was the first medusahead detection in Wyoming and the Great Plains Eco Region. Ventenata has been found in six of Wyoming’s 23 counties, but is so far contained in the northeast corner of the state.”
The state responded to those detections with a work group of some 30 different state, federal and local agencies, private citizens and non-governmental organizations.
“Everyone got involved in a collective management effort and we started meeting annually in 2017,” Arndt said. “Our goal was landscape-scale treatment. It was a large effort and we were learning as we went. It was like flying a plane as we were still building it.”
The metaphor proved pretty apt. Early large-scale treatments of aerially applied herbicide were conducted by airplanes but the team learned those application was too imprecise. They now uses helicopters for aerial spraying.
In 2020, the state provided new funding to establish the Institute for Managing Annual Grasses Invading Natural Ecosystems, or IMAGINE, within the university. Arndt is its coordinator.
“Our goal is to improve annual grass management throughout the state through research, monitoring and treatment, and to assist the West regionally through a tech-transfer program of what we learn here,” she explained.
The monitoring network has active partners in 18 of Wyoming’s 23 counties, and employes 13 student interns who conduct monitoring all summer.
“We’ll have collected more than 18,000 data points just this summer,” Arndt said.
That monitoring has enabled the program to develop detailed maps of invaded areas to develop priority treatment and restoration targets. After a recent wildfire in Johnson County, for instance, officials want to reseed native sagebrush in burned areas. The institute was able to identify areas within the burn scar that had high sagebrush presence pre-fire, that also had low annual grass cover, a northeastern aspect and less than 5 percent slope.
Four areas that met those criteria were aerially seeded for sagebrush, a first for Wyoming, and sage did establish in one of the seeded areas.
Most of the project’s annual grass treatments are herbicides, and the group conducts ongoing research to maximize their efficacy and minimize off-target impacts. The research includes trials of different herbicides (and different combinations and concentrations of those herbicides), as well as grazing and other pre-treatment research.
“One thing that is clear is that annual grasses are a lot cheaper to control at low invasion levels,” Arndt said. “At high levels of degradation, the restoration required is much more expensive and difficult.”
So the work will continue, trying to contain ventenata to the six-county corner of the state, and to eradicate medusahead if possible (or at least keep it contained at low levels in Sheridan County.)
“Wyoming is leading in these efforts,” Arndt said. “The state has committed more resources than anyone in the West, and treated more acres, to keep these invasive annual grasses from taking over our lands.”