Typhoon-related tree damage and conservation implications for homestead windbreaks on the Ryukyu Archipelago: a case study of Yonaguni Island, Japan

Homestead windbreaks are used on the Ryukyu Islands to protect houses from the tidal water blowing from the sea, strong typhoons in the summer, and monsoonal winds in the winter. The homestead windbreak landscape is believed to have been established approximately 300 years ago in the Ryukyu Kingdom. Garcinia subelliptica (Fukugi in Japanese) was dominant in this windbreak landscape. These windbreaks vanished on several islands soon after World War II. Many trees were burned during the war and removed to extend village roads in rural and recent resort development projects. This study surveyed the present spatial distribution of the remaining homestead windbreaks and conducted a tree inventory survey. We recorded the location and characteristics of trees damaged by the powerful typhoon and tentatively explored the causes of tree and house damage through a case study of Yonaguni Island, where one of the world’s biggest typhoons occurred. Homestead windbreaks facing the wind direction, tree characters of cavities, unsound branching, and combined tree trunks were the significant factors contributing to tree damage. The remnant homestead windbreak belts in Yonaguni Island were fragmented and not continuous and may not offer consistent wind protection since there are open gaps between the sections. It suggests windbreaks should be replanted in the direction of the wind, and regular checks of tree health and tree structure are needed to reduce typhoon damage. The results are used to propose guidelines for windbreak management and conservation.