Diversity of species and functional groups and richness (number) of species are useful information fro understanding ecosystem stability. Narrower measures of diversity, for example within one zone or ecosystem type or for one taxonomic group (e.g., birds) could provide more interpretable information than measuring the entire diversity of an area. Rocky intertidal areas are probably the most feasible place to collect data for this indicator, though this system type is also subject to dramatic natural and artificial disturbances.