Assessing Resilience of Western Rangelands to Transportation-Related Land-Use Change

The amount and extent of transportation related activity in western rangelands has rapidly increased in recent decades. This increase is due to a variety of factors including oil and gas development, recreational activities, and ex-urban development. In addition to areas directly impacted by infrastructure installation, the presence and use of these travelways has potentially altered the resilience of adjoining areas through indirect effects such as altered site hydrologic and eolian processes, invasive seed dispersal, and sediment transport. Direct and indirect impacts of these networks are of particular concern in ecosystems with inherently low resilience, such as those with aridic soils. There is little guidance, however, on appropriate methods for assessing and monitoring the impacts of transportation related land-use activities on soils and vegetation. We tested the sensitivity of a qualitative assessment technique (Interpreting Indicators of Rangeland Health) and quantitative measures to roads, trails, and pipelines. The protocols used have a demonstrated connection to soil nutrient and moisture-related processes in a wide range of ecosystems. We conducted surveys at plots near, far and very far from travelways at 16 sites selected using a stratified random sampling design in 3 ecosystems for a total of 208 plots evaluated. Results indicate that qualitative techniques are sensitive to direct and indirect impacts of transportation activities. Additionally, differences detected with qualitative techniques between areas near, far and very far from disturbances followed the same trends and were highly correlated with quantitative measures. The qualitative and quantitative assessment techniques employed in this study can be used to assess impacts of individual transportation features or to assess cumulative impacts of a transportation network. Assessing how transportation related activities on western rangelands affects ecosystem resilience is crucial for understanding how these systems will respond to the warmer and drier conditions predicted as a result of global climate change.