Potential Climate Change Impacts on Four Biophysical Indicators of Cattle Production from Western US Rangelands

Abstract

We examined multiple environmental factors related to climate change that affect cattle production on rangelands to identify sources of vulnerability among seven regions of the western United States. Climate change effects were projected to 2100 using published spatially explicit model output for four indicators of vulnerability: forage quantity, vegetation type trajectory, heat stress, and interannual forage variability. Departure of projections from the baseline (2001–2010) was used to estimate vulnerability of present-day cattle operations. The analysis indicated 1) an increase in forage quantity in northern regions; 2) a move from woody dominance toward grassier vegetation types overall but with considerable spatial heterogeneity; 3) a substantial increase in the number of heat-stress days across all regions beginning as early as 2020–2030; and 4) higher interannual variability of forage quantity for most regions. All four factors evaluated in tandem suggest declining production in southern and western regions. In northern and interior regions, the benefits of increased net primary productivity or increasing abundance of herbaceous vegetation are mostly tempered by increases in heat stress and forage variability. Multiple indicators point toward increasing vulnerability of cattle production in southwestern regions providing strong support for the need for adaptation measures and suggest significant change to the industry. Opposing indicators in northern regions point toward the need for cattle operations to increase flexibility to take advantage of periods of favorable production while preparing for uncertainty, variability, and increasing stress from individual factors.