Pinyon-juniper (Pinus spp.-Juniperus spp.) woodlands are estimated to cover 24 to 40 million hectares (ha; 59 to 99 million acres) in the Intermountain West and are distributed extensively across the Colorado Plateau (Samuels and Betancourt, 1982). The distribution of these woodlands has expanded and contracted throughout history (Tausch, 1999), and expansion is presently occurring at a high rate (Miller and Wigand, 1994). Possible catalysts to this rapid expansion include historical fire suppression and livestock grazing (Harris and others, 2003; Johnsen, 1962; Miller and Rose, 1999; West, 1984), coupled with climate change (Bradshaw and Reveal, 1943; Gray and others, 2006). Recently, drought associated with climate change, coupled with bark-beetle infestations, have resulted in large areas of pinyon mortality (Breshears and others, 2005).