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As temperatures grow hotter, cheatgrass, invasive species thrive in Montana, the West – Daily Montanan [1]

['Sage Sutcliffe', 'More From Author', '- Sunday July']

Date: 2023-07-30  

Cheatgrass (Photo by Justin Fritscher | NRCS).

The West’s sagebrush and native shrub rangelands are dwindling faster than the Amazon rainforest.

Invasive annual grasses like cheatgrass are the culprit, according to a team of researchers from the University of Montana and United States Department of Agriculture researchers in Oregon.

Published in October 2021 in the “Diversity and Distributions“ journal, the research indicates that in a warming climate, the grasses are becoming better suited to thrive in higher elevations and on north-facing slopes where they were previously scarce.

Cheatgrass may be the most villainized of the grasses, but red brome, medusahead and ventenata are just as bad. Together, the annual grasses dominate many Great Basin ecosystems and cover more land than native, perennial species like sagebrush.

This phenomenon poses risks to people, wildlife and native rangelands. The annual grasses included in the study are a fine fuel, increasing the frequency and intensity of wildfire cycles. The grasses also reduce biodiversity and threaten native species like sage grouse, which depend on intact sagebrush habitat to thrive.

While mapping annual grass trends in Google Earth Engine, Joe Smith, a rangeland ecologist in UM’s Working Lands for Wildlife lab, noticed an expansion of grasses spreading into areas they had not been.

Using the Great Basin region as their study scope, Smith and his research team utilized a satellite imagery tool, Rangeland Analysis Platform, to calculate the spatial change in land cover types during a 30-year period. Paired with field data gathered from the U.S. Bureau of Land Management that differentiates between the native shrubs and invasive grasses, the researchers determined an 800% increase in area dominated by grasses from 1990 to 2020.

The use of the RAP data—generated from satellite imagery—alongside data gathered from fieldwork is a relatively new research method that emerged in 2016. It is also an important advancement, according to Madelon Case, Supervisory Rangeland Research Ecologist with the U.S. Geological Survey in Corvallis, Oregon, who was not involved with the research completed by Smith.

“It’s an example of technological advancements in rangeland monitoring,” Case said. “These datasets that are based on combining satellite imagery and validation data from thousands of field plots give researchers new abilities to document change at broad scales.”

The high rate of change in rangeland ecosystems worries Smith. An Oregon native, he grew up just outside of the Great Basin region and knew cheatgrass, in particular, was a problem long before he began studying wildlife biology and annual grasses. His findings sounded yet another alarm that cheatgrass is a rising threat. It also spurred innovation that offers solutions.

After viewing Smith’s cheatgrass maps, Jeremy Maestas—a WLFW team member and National Sagebrush Ecosystem Specialist with the Natural Resources Conservation Service in Bend, Oregon—and his colleagues devised a new strategy called “Defend the Core “to proactively combat cheatgrass. Officially launched in 2022, the approach uses remotely sensed vegetation data to map intact, healthy shrubland “cores.” Once identified, proactive pulling and spraying practices are employed to ensure those cores are defended from threat of invasive grasses. Cores can be expanded with additional conservation measures to push back against the invasion, ultimately resulting in larger, healthier core areas over time.

Ecologists like Smith, Case and Maestas are keenly aware of the problems annual grasses pose to the West’s expansive rangelands. Case said the ecological community is keeping a close watch through RAP’s “bigger picture” lens as the grasses continue to encroach into new areas of rangelands as the climate warms.

“The invasion of these annual grasses is an ongoing phenomenon,” Smith said. “It’s not over.”

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[1] Url: https://dailymontanan.com/2023/07/30/as-temperatures-grow-hotter-cheatgrass-invasive-species-thrive-in-montana-the-west/

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