Quantifying spatiotemporal changes in a sagebrush ecosystem in relation to energy development

Energy development has been occurring in the intermountain western United States for over a century, yet few studies have attempted to spatially quantify the impacts of this disturbance on native ecosystems. We used temporal remotely sensed data for the Pinedale Anticline Project Area (PAPA) in western Wyoming, a region that has experienced increased natural gas development within the past 10 yr, to quantify the spatiotemporal distribution of Wyoming big sagebrush Artemisia tridentata, natural gas development, and other landcover types. Our analyses included 5 Landsat Thematic Mapper (TM) images of the PAPA over a 22-yr period (1985-2006). We determined whether Wyoming big sagebrush spatiotemporal patterns were associated with natural gas development or other landcover types. We also developed a footprint model to determine the direct and indirect impacts of natural gas development on the distribution of Wyoming big sagebrush habitats. Over the 22-yr period, we observed an inverse relationship between the amount of Wyoming big sagebrush habitat and natural gas development. During this time, Wyoming big sagebrush habitat declined linearly at a rate of 0.2% yr-1 (4.5% total net loss), whereas natural gas development increased exponentially at a rate of 20% yr-1 (4800% total net increase). Our evaluation indicated that, by 2006, natural gas development directly impacted 2.7% (1750 ha) of original Wyoming big sagebrush habitat. Indirect impacts, quantified to account for degraded habitat quality, affected as much as 58.5% (assuming 1000-m buffers) of the original Wyoming big sagebrush habitat. Integrating assessments of the direct and indirect impacts will yield a better elucidation of the overall effects of disturbances on ecosystem function and quality.