Son of a beach: Coastal development and the loss of natural beaches over time (1919 to 2018) on Okinawa Island, southern Japan.

The coastline of Okinawa Island, Japan, has been affected by human-made alterations for decades, often from land reclamation and coastal defense construction. Here, we use an Imperial Japanese Army map made between 1919 and 1921 to describe the composition of the Okinawan coastline approximately 100 years ago, and by overlapping this old map with a modern-day map of Okinawa (2018), we identified 131 sites where coastlines showed clear human-made alterations. For these sites, we examined what kinds of ecosystems were lost and what has replaced them. These data show losses of river mouths, tidal areas, rocky shores, natural sandy beaches, inner and outer reefs, and gains of industrial sites, ports, residential areas, agricultural areas, artificial beaches, military complexes, and vacant land. Considering the wide-scale alteration that has already occurred and the ecosystem services that coastal marine ecosystems provide, conservation of remaining natural coastlines of Okinawa Island should be given priority.