Level of Geographical Subdivision and Its Effects on Assessments of Reserve Coverage: A Review of Regional Studies

Land classes such as vegetation types, ecoregions, or environmental domains can be defined in many ways and at many scales. We set out to quantify the influence of the level of subdivision of land classes on the extent to which the classes are represented in reserves. We examined data on the occurrence of land classes at two or more levels of subdivision in many regional reserve systems. Reserve coverage (the percentage of land classes represented in reserve systems) usually changed as the classes were defined more finely. The extent and general direction of change depended on the reservation threshold or percentage area of land classes needed in the reserve system before they were called "reserved." The results indicate the need to qualify assessments of reserve coverage as dependent on the level of subdivision. They also raise the question of the most appropriate levels of subdivision for such assessments. A definitive answer requires more research on the informativeness of land classes about the biota.