The aim of this study was to evaluate the comparative importance of habitat types for the conservation of biodiversity. We determined the number of endangered vascular plant species for each habitat type using the regional Red Data Book that contains information for five prefectures in the Chugoku region, western Japan, together with data on the area covered by each habitat type obtained from the fifth national vegetation survey. The habitat types were classified as "forest", "agricultural field," "wetland," "rocky ground," "grassland," or "seaside." Although many of the listed endangered species belonged to forest habitats, at the regional level, the species/area ratios were higher in the grassland, wetland, and seaside habitats than in the forest and agricultural field habitats. However, the conservation priorities for the endangered plant species in relation to habitat type showed only a slight variation among the prefectures examined.
Echinops setifer is an endangered perennial herb found in semi-natural grassland in the Tokai, Chugoku, and Kyushu regions of Japan. To elucidate the status of E. setifer populations on Aso Mountain and Chugoku Mountain regions, we conducted field surveys and genetic analysis using microsatellite markers for all known populations in these two regions. Field surveys revealed the existence of only several tens of mature individuals in each population and a decrease in the number of mature individuals in most populations. Analysis of genetic diversity showed that the diversity of the remnant population was relatively low on Aso Mountain. In nearly half of all cases, the vegetation in E. setifer habitats has dramatically changed due to a change in, or abandonment of, traditional grassland management systems in recent decades. The change in grassland vegetation threatens the continued existence of E. setifer individuals. Thus, maintenance and monitoring of vegetation in the habitats of this plant are essential for E. setifer conservation programs.
Recently, local governments in Japan have published Red Data Books as a baseline for regional biodiversity management. However, these books often lack explicit criteria for selecting endangered species and the detailed information required for implementation of effective conservation programs. Considering these problems, we compiled a Red Data Book of endangered vascular plant species for Ushiku City, Ibaraki Prefecture, based on an objective approach. We also tried to infer practical measures required for conservation of each species described in the new book.