Evaluation of beach vegetation for conservation/rehabilitation in Tottori Prefecture, Southwest Japan

摘要

We examined 17 beaches in Tottori Prefecture to evaluate the current status of beach vegetation for conservation/rehabilitation purposes. We conducted a floristic survey and a beach vegetation status survey, and analyzed the beach environment using aerial photographs and a geographic information system. The health of the beach vegetation was evaluated by principal component analysis (PCA) of beach vegetation and environmental variables. PCA of beach vegetation variables, where axis 1 represented the scale of beach vegetation and axis 2 represented the quality of beach vegetation, resulted in four categories. PCA of beach environment variables, with axis 1 representing the synthetic component of grain/area/extension and axis 2 representing beach widths, also resulted in four categories. A beach vegetation list was determined from a floristic survey, and three conclusions were made based on this list. We first determined the priority of the beach plant species with regard to conservation. Based on their occurrence, the beach plants were divided into four types that were ordered with regard to their priority for beach plant conservation. We next focused on the occurrence of beach plants listed in the Red data book for Tottori Prefecture and reexamined the validity of the extinction risk category. Our conclusion was that this category needs to be updated. Finally, we compared the number of beach plant species of the survey site beaches with that of the Tottori Sand Dunes, where more natural conditions prevail. We found that only seven beaches equaled or surpassed the Tottori Sand Dunes in terms of the number of plant species. Based on these findings, we concluded that beaches other than the Tottori Sand Dunes are in need of conservation/rehabilitation.