Abstract
To be effective in biodiversity conservation, spatial conservation planning should consider the complementarity among planning units. Complementarity is one of the central concepts in spatial conservation prioritization, and complementarity analysis based on the concept is becoming a major method both in research and in practice dealing with spatial problems in conservation planning. Marxan is the most popular tool to implement the complementarity analysis that can give us the most efficient solutions, a set of prioritized areas, based on conservation features, their spatial distributions and conservation target set to each of them. Efficiency here is defined as a function of size, shape and arrangement of prioritized areas, and conservation cost of selected planning units, and degree to which each of conservation targets has been attained. Recently, complementarity analysis using Marxan was applied to a nation-wide biodiversity mapping project for the first time in Japan. Specifically, it was used to identify the set of candidate areas for the efficient conservation of endangered vascular plants in the county. The number of applications of complementarity analysis to conservation practices is expected to grow rapidly at every taxa and spatial scales from national to local. Practitioners, however, must always keep in mind that results and effectiveness of the analysis can be very sensitive to uncertainty in available information on spatial distribution of conservation features and to adequacy of conservation actions taken in the selected planning units.
