The site is situated in the southwest of Kochi Prefecture. Influenced by the Japan Current the climate of the islands is warm with a relatively high temperature and high humidity. Many plants with subtropical features grow. In the sea bottoms groups of reef forming beautiful hermatypics are in existence. Fish are also abundant and diversified. Okinoshima is consisted of granite and there are series of cliffs eroded by seawater and steep slopes. In Biroujima there are communities of herbaceous plants, and also communities of Machilus tunbergii are seen.
BirdLife International (2020) Important Bird Areas factsheet: Seinan islands. Downloaded from
http://www.birdlife.org on 25/09/2020.