The Problem: Annual Grasses

Across the Great Basin, invasion of annual grasses, especially cheatgrass (Bromus tectorum), is altering natural fire regimes and converting large expanses of the sagebrush sea to an ocean of non-native annual grass. The combination of large scale wildfire and exotic annual grasses poses a formidable threat to sage-grouse and their habitats. This topic guides you through understanding the problem and science behind invasive grasses as well as management tools you can use to help fight this invasion.

Watch the video below for an introduction to the problem casued by the non-native, invasive cheat grass by Dr. Brian Mealor from the University of Wyoming.

Wildfire and the associated conversion of low- to mid-elevation sagebrush habitats to invasive annual grass-dominated vegetation communities are the two primary threats to the sustainability of sage-grouse as mentioned by the U.S. Fish and Wildlife Service in its Conservation Objectives Team report and the Western Association of Fish and Wildlife Agencies in its invasive species report.

This topic discusses fuels and vegetation management practices in areas dominated by or at risk from annual invasive grasses, including linear fuels treatments and targeted grazing treatments. It addresses primarily the western (Great Basin) range, where the invasive grass/fire cycle is a critical threat. Annual grass invasion is an emerging threat in the eastern (Rocky Mountains) range, though issues specific to that region are discussed more in the lesson on the Eastern Range.

The topic also introduces the Resistance and Resilience concept, which helps to define resistance to annual grass invasion and other considerations influencing treatment type and options; more detail is provided in the lesson on Resistance and Resilience.

 


How large is the invasion of annual grasses?

General estimate

By some estimates (e.g., Davies et al. 2011), it is thought that 5.7 million ha (14.1 million ac) of publicly-owned lands in the Intermountain West are infested with exotic annual grasses (medusahead, Taeniatherum caput-medusae; cheatgrass; North Africa grass, Ventenata dubia; or combinations of the three).

However, this same study concludes that the area at risk of invasion by these grasses is at least 25 million ha (61.8 million ac), or an area over 4 times greater.

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Cheatgrass estimates in the Intermountain West

A map characterizing risk of cheatgrass invasion (Meinke et al. 2009) estimated a moderate to high probability of cheatgrass dominance on 28 million ha (69.2 million ac) in the Intermountain West in Idaho, Oregon, Nevada, Utah, and Washington alone.

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Cheatgrass estimates in the northern Great Basin

Examine the updated (2016) map of predicted cheatgrass cover in the northern Great Basin. This map is the result of using the Boyte et al. (2015) methodology of cheatgrass cover prediction, which used multiple ecological models integrating remote sensing data from the enhanced Moderate Resolution Imaging Spectroradiometer (eMODIS) Normalized Difference Vegetation Index at 250m spatial resolution with geophysical and biophysical data.

The map can be interpreted as showing the current cover of cheatgrass in the Northern Great Basin and can be used to characterize the relative dominance of cheatgrass over broad landscapes

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This topic will guide you through the science behind invasive annual grass and wildfire relationships and will present you with land management tools you can use to address this issue. To get started, select a section in the navigation above. You may complete the sections in order, or you may visit each in any order you choose.

Select Science to continue.


Interesting Facts

30

The number of species
of plants that are
considered invasive
in sagebrush ecosystems.

69,200,000

The number of acres
at risk of invasion
by exotic annual grasses
in the Great Basin.

557,648

The number of acres
burned in the Long Draw Fire
in southeastern Oregon
in 2012.