Looking for important plant areas: selection based on criteria, complementarity, or both?

The goal of the Global strategy for plant conservation (GSPC) was to protect 50 % of the most important areas for plant diversity by 2010; such areas are defined as the most important places in the world for wild plant diversity, identified according to common criteria. Although the concept of complementarity is intrinsically included in the GSPC, it is not widely used in the IPA definition process. We compared the results of a criteria-based selection approach to the identification of the Important Plant Areas with those of a systematic conservation approach to assess the benefits of integrating these two methods. The criteria-based definition was composed of a ranking procedure that identified 351 top ranking cells containing high conservation value species/habitats and/or richness. The complementarity approach selected 265 cells. The results were compared in terms of beta-diversity and land cover. A weak, though significant association emerged between the results; moreover, the criteria-based approach unexpectedly proved to be more effective in selecting beta-diversity than the complementarity approach. In terms of land cover composition, the cells proposed by the two selection methods differed significantly, with the criteria-based approach selecting natural and seminatural areas and the complementarity approach selecting agricultural areas. The comparison of the two approaches that are used to define Important Plant Areas on a national scale demonstrated that the explicit inclusion of the systematic conservation approach in the IPA process may help to integrate the designation of IPAs, to locate critical areas and address the needed further investigations in selected zones.