Growth of mangrove forests and the influence on flood disaster at Amami Oshima Island, Japan

“Mangrove” is the generic name for plants growing on tropical and subtropical tidal flats. The mangrove is used for many things, including disaster protecting land from high waves and tides and tsunamis, cleaning rivers and drainage containing soil and sand, and providing a variety of organisms with living space. Climate change and rising sea levels are threatening the future of the mangrove. Developing effective ways to conserve mangroves is thus needed, but more must be known about how the mangrove’s ecology and how it develops. It has been pointed out, for example, that mangroves increased flooding by the Sumiyo River in Amami Oshima. We studied ways to develop the mangrove at the Sumiyo River mouth in Amami Oshima and its influence in local flooding, finding that the current mangrove forest had little influence on flooding and that sediment deposition accelerating in Sumiyo Bay due to a sea dike could enlarge the mangrove forest in future.