Biological models for monitoring species decline: the construction and use of data bases

Abstract We describe procedures for designing ecological surveys and analysing survey data which more accurately estimate the spatial distribution patterns of species than the opportunistic or ad hoc biological field collections generally available. Surveys should be based on an environmental stratification, and the data collected should be sufficient to enable statistical estimates of wider spatial distribution patterns to be made from the point sample sites of the survey itself. Without such ecological data bases of high quality, accurate estimates of extinction rates will remain problematical, that is, confined to single populations and geographically restricted