IDENTIFYING GAPS IN CONSERVATION NETWORKS - OF INDICATORS AND UNCERTAINTY IN GEOGRAPHIC-BASED ANALYSES

Mapping of biodiversity elements to expose gaps in conservation networ ks has become a common strategy in nature-reserve design. We review a set of critical assumptions and issues that influence the interpretati on and implementation of gap analysis, including: (1) the assumption t hat a subset of taxa can be used to indicate overall diversity pattern s, and (2) the impact of uncertainty and error propagation in reserve design. We focus our review on species diversity patterns and use data from peer-reviewed literature or extant state-level databases to test specific predictions implied by these assumptions. Support for the bi odiversity indicator assumption was varied. Patterns of diversity as r eflected in species counts, coincidence of hot spots, and representati veness were not generally concordant among different taxa, with the de gree of concordance depending on the measure of diversity used, the ta xa examined, and the scale of analysis. Simulated errors in predicting the occurrence of individual species indicated that substantial diffe rences in reserve-boundary recommendations could occur when uncertaint y is incorporated into the analysis. Furthermore, focusing exclusively on vegetation and species distribution patterns in conservation plann ing will contribute to reserve-design uncertainty unless the processes behind the patterns are understood. To deal with these issues, reserv e planners should base reserve design on the best available, albeit in complete, data; should attempt to define those ecological circumstance s when the indicator assumption is defensible; should incorporate unce rtainty explicitly in mapped displays of biodiversity elements; and sh ould simultaneously consider pattern and process in reserve-design pro blems.