Invasion Severity Index

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Invasive annual grasses (IAG) pose one of the most significant and rapidly expanding threats to rangeland health across the western United States. These exotic grasses include cheatgrass, medusahead, and ventenata, and when they overtake rangelands, they alter fire regimes, reduce habitat quality, and diminish long-term productivity. Developing effective management strategies and treatment prescriptions requires an understanding of the degree of invasion in an ecological context, including site potential, competitive balance with perennial grasses and forbs, and overall productivity. The Invasion Severity Index (ISI) maps and web app provide a simple, interactive platform to help conservation planners and land managers prioritize and plan invasive annual grass treatments across the sagebrush biome. Using cutting-edge Rangeland Analysis Platform (RAP) 10-meter resolution data, ISI maps depict five invasion levels linked to specific management strategies and actions. The ISI assesses the severity of annual grass invasion relative to perennial forb and grass cover and bare ground, providing an ecologically grounded framework for prioritizing management and aligning treatment techniques with site resilience and recovery potential. Other reference layers and features allow users to understand landscape context, consider trends through time, visualize specific vegetative thresholds, and generate time series charts.