Effectiveness of land classes as surrogates for species in conservation planning for the Cape Floristic Region

Land classes are often used in conservation planning as surrogates for species. The relationship between these surrogates and the distribution of species is usually assumed but rarely tested. Using broad habitat units (BHUs) to represent biodiversity pattern in the Cape Floristic Region, together with point locality data for species (proteas and selected vertebrates), we calculated the effectiveness of BHUs as surrogates for species. Our planning units were grid cells of about 40 km(2), together with boundaries of existing reserves. After assigning conservation targets to BHUs, we derived minimum sets of planning units to meet all targets and calculated irreplaceability values for all units (irreplaceability measures the likelihood of a unit being required to achieve targets). Results showed that BHUs were good surrogates for the majority of protea species, but were not good surrogates for vertebrate species or for a small subset of protea species. These species shared the following characteristics: rarity, limited ranges, Red Data Book status, specialised habitats not defined by BHUs, and distributions driven by historical rather than contemporary ecological factors. We show that targeting land classes and species simultaneously is a viable option and requires only 0.1-0.8% more land (depending on species targets) than targeting land classes alone. We conclude by recommending two different strategies for combining land class and species data in conservation planning, depending on data availability.. (C) 2003 Elsevier Science Ltd. All rights reserved.