Development of mapping methods for macrophyte beds in Japan by using ALOS AVNIR-2

摘要

In coastal waters, macrophyte beds (seagrass and seaweed beds) are important habitats for many marine organisms. However, decrease in macrophyte beds has been reported in all over Japan. Seagrass and seaweed are considered to be affected by climate changes or human impacts. Mapping and monitoring of seagrass and seaweed distributions are necessary for revealing the mechanism of their decrease and making counter measures for those conservation and restoration. Satellite remote sensing is thought to be one of the most efficient methods for macrophyte beds mapping because a satellite image covers a large area at once and making mosaic is relatively easy compared with that of aerial photographs. So far, some researchers have studied on seagrass mapping and a few researchers also focused on seaweed beds. Most of studies on macrophyte bed mapping have limited in areas of test sites. Only a few studies focus on national scale mapping using a set of satellite images. This study was conducted as a part of JAXA projects aiming to develop methods for mapping seagrass and seaweed beds all over Japan. ALOS/AVNIR-2 images were selected for analysis because its spatial resolution (10m) is high enough to cover almost all Japanese coast with its archived images for mapping. Four geographically separated sites were selected as test sites focusing on differences in dominant species of four sites, Ecklonia cava, Eisenia.