Although conservation and management of tropical ecosystems requires that we understand the threats to these areas, there are no standardized methods to quantify threats to ecosystems.We used a geographic information system-based protocol with several physical and socioeconomic attributes to assess the threats to a protected area, a wildlife sanctuary in southern India. Physical attributes included threats from major and minor roads and the accessibility of an area (given as inverse of the slope of the area), and socioeconomic attributes included the number of human settlements and human, cattle, and sheep populations.We divided the sanctuary into 30-ha grids, and for each grid we computed three threat categories: (1) settlement-associated threat from humans, cattle, and sheep; (2) development-associated threat resulting from major and minor roads; and (3) accessibility-related threat caused by the steepness of the terrain. Combining all three threats, we derived a composite threat index for each grid and mapped five levels of threats in the sanctuary.We collected data on human activities, tree species richness, and diversity in the transects laid in areas corresponding to these five threat levels. Although the threat levels of the transects were strongly correlated with the humanrelated disturbance activities, the composite threat indices of the transects were negatively correlated with tree species richness, indicating that the threat values we derived served as a good surrogate of the actual threat experienced by the sanctuary. With appropriate modifications, the protocol developed here can be applied to other ecosystems as well.