Global Short Term Trend: Relatively stable to increase of 25%
Comments: Flora of North America includes Mojave Desert, Owens Valley, and Colorado Plateau populations within subspecies parishii. Beetle (1960) estimated that the most widespread subspecies (vaseyana) dominates an area of approximately 260,000 square kilometers. That estimate remains reasonably accurate today even though sagebrush is often cleared (by burning, herbicide spray, or the practice of 'chaining') and replaced by grasses (especially crested wheatgrass) suitable for livestock grazing. The acreage in which sagebrush has been removed appears to be more than compensated by acreage where it has increased in abundance because of overgrazing. On drier sites and on high plateaus, subspecies tridentata is replaced by subsp. wyomingensis, a taxon that appears to be increasing with prolonged droughts and disturbance from grazing. Subspecies wyomingensis may be increasing in abundance in response to increased grazing pressure and drought in the high valleys of the Great Basin.
Global Long Term Trend: Increase of 10-25% to decline of 30%
Comments: Western juniper (Juniperus occidentalis) is intolerant of fire and historically was kept in restricted sites by natural fires. Since the advent of effective fire control and intensive livestock grazing (reducing ground fuel and understory competition), regeneration and establishment of western juniper have expanded into suitable sites previously dominated by mountain big sagebrush (Artemisia tridentata spp. vaseyana). This expansion of young stands is common in Oregon, Idaho, and northeastern California (Burns and Honkala, 1990).