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Submodule 3: Economic and Ecological Impacts

Cheatgrass

Cheatgrass (Bromus tectorum) is also commonly known as downy brome and early cress. It is a winter annual that produces vast quantities of seed, its primary mode of reproduction. Like most grasses, it has fibrous roots that can provide support for holding soil and decreasing erosion. Cheatgrass is native to parts of Europe, Africa, the Middle East, and Asia. As with most invasive plants, cheatgrass primarily invades habitats that are similar to its native habitat. Genetic studies have revealed that the weed was introduced into the U.S. numerous times from many different locations. The grass found in the western U.S. originated primarily from Europe, the origin of most settlers in this region. In 1994, it was reported that cheatgrass infested almost 17 million acres of BLM (Bureau of Land Management) land in Nevada, Oregon, Washington, Utah, and Idaho. This grass can exist as a complete ground cover or as understory accompanying native plant communities. In 2003, estimates of infestations totaling 56 million acres were reported. Cheatgrass can grow in a wide range of habitats and environmental conditions, which enhances its ability to spread over large areas. Infested areas are particularly prone to altered fire patterns due to increased fuel from dry cheatgrass. Being a winter annual, this weed germinates in the fall, continues growth in the spring, and by summertime has already produced seeds and begun senescence. This growth behavior leads to a large amount of fuel for late summer and fall fires and has changed fire patterns for much of the land infested by cheatgrass.

 

In spite of its invasive nature, cheatgrass is a valuable forage grass in some areas. Cattle, horses and sheep graze on the grass, especially in the early spring. Since it is a winter annual, it produces seed and dries early in the season so its value is of limited duration. Also, the amount of cheatgrass biomass produced on a year-to-year basis changes drastically, depending primarily on available precipitation.

 

Economic Impacts of Cheatgrass

• Cheatgrass invades rangeland as well as valuable agricultural lands, decreasing the property values of both. It is especially a problem in alfalfa and winter wheat fields where it can drastically decrease the biomass of these crops. It has been estimated that cheatgrass infests up to 46 million acres of winter wheat costing growers about $300 million annually in lost crop yield. These growers spend an additional $70 million in herbicides to control the weed.
• Researchers have found that cheatgrass decreases the production of desired crops both in cultivation and on rangelands, with seed yield for some grasses reduced by up to 68% on infested lands.
• Areas infested by cheatgrass often have increased fire frequency. Associated costs for fighting these fires and rehabilitation in their aftermath have been estimated at about $15 million yearly in southern Idaho alone.

Ecological Impacts of Cheatgrass

• Ecological costs of altered fire patterns can decrease the ability of native annuals and especially perennials to re-establish after a fire event, while cheatgrass is able to thrive in such conditions.
• Alterations in native plant communities often lead to negative impacts on native animals, for example, habitats and food sources for small mammals can be destroyed by cheatgrass infestations, which in turn causes a decrease in food for predators.
• Cheatgrass is able to grow at wider temperature ranges than many native grasses, which improves their ability to overtake native plant communities.
• Cheatgrass depletes soil moisture faster than native plants, which can increase its adaptive advantage.
• It is known to decrease soil nutrients faster than native plant species.
• Several wild animals will eat cheatgrass, especially when natives and other more palatable forage has been destroyed by fire or by encroachment of other invasive plants. However, research has shown that areas of native vegetation are able to support much larger populations of wildlife than those dominated by cheatgrass.
• Cheatgrass has a major negative impact on rare and threatened plant species. A decline in the population size of several native species has been directly attributed to invasions of cheatgrass.
• This grass is able to invade relatively healthy rangeland communities of many different types in addition to disturbed areas.
• Some ecologists have even predicted that native ecosystems will permanently disappear as a result of cheatgrass dominance; this has begun to happen in the Great Basin of Nevada and in the Mohave Desert of southern California.

 

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