Cheatgrass invasion and woody species encroachment in the Great Basin: Benefits of conservation

Abstract

The Great Basin is the largest North American desert, covering more than 49.6 million ha (122.5 million ac), and includes most of Nevada, a large part of Utah, and smaller sections of Oregon, Idaho, and California. Two of the biggest threats to ecosystem stability and integrity in the Great Basin are invasive annual grasses, particularly cheatgrass (Bromus tectorum L.), and expansion of native woody plants, particularly juniper (Juniperus spp.) species and pinyon pines (Pinus monophylla Torr. and Frém. and Pinus edulis Engelm.). An estimated 72% (36 million ha [88 million ac]) of the Great Basin is currently impacted by cheatgrass (Pellant et al. 2004). Pinyon and juniper woodlands currently occupy approximately 22.5 million ha (55.6 million ac) throughout the western United States (Miller et al. 2011). In the Great Basin alone, the occupied area is nearly 7.1 million ha (17.5 million ac), the result of a 125% to 625% increase in tree distribution, much of which occurred in areas where these species were not inherent components of the plant community (Miller et al. 2008).