Cheatgrass (Bromus tectorum) was introduced into the western United States as a food for livestock foraging on arid lands, such as the Great Basin Desert. It quickly proved to be a huge mistake, not only because the time frame for eating by cattle and sheep herds was so limited (after a short stretch in early spring, the grass becomes inedible), but also because the grass quickly invaded both the old growth Pinon Pine / Juniper forest and Big Sage desert ecosystems with exceptionally disastrous effects.

According to Peter Weisberg of the Online Nevada Encyclopedia, once introduced, the big problem with cheatgrass is this:

Cheatgrass is able to alter natural fire conditions through its particular life history characteristics. Cheatgrass has a winter annual life cycle that differs from that of most native grasses. Seeds germinate in fall or early winter so that established plants grow rapidly in early spring as a result of their head start. Abundant seeds are produced and the plant's life cycle is completed in early summer, while native bunchgrasses are still green and not yet reproductively mature. Dry, dead cheatgrass burns readily and produces a continuous layer of fuel to carry range fires. The resulting fires put native vegetation at a disadvantage because many species have not yet set seed. A positive feedback loop is created; with each successive fire, cheatgrass becomes more dominant.