This indicator is envisioned as a way to address a problem inherent in simple measures of recreation use: rangeland sustainability is influenced by the ecological and social impacts of recreation use, and these impacts are not necessarily correlated with user density. Biophysical impacts of recreation typically follow a curvilinear pattern where marginal changes in impacts (e.g., soil compaction, change in plant species composition) become smaller as use levels increase. As a result, changes in visitor numbers may or may not indicate loss of additional value at the site level, depending on whether use is already low, moderate, or high. Social impacts of recreation – crowding, conflict between user groups, and depreciative behaviors (vandalism, littering, rule violation, etc.) – are more dependent on characteristics of the use and users than on simple numbers of users.