The Nature of Ogasawara and its Conservation

抄録

　The Ogasawara (Bonin) Islands are oceanic islands in the northwest Pacific Ocean. Their origin goes back to the Tertiary, the present islands having emerged at least several million years ago. The climate is subtropical and typhoons pass by the islands every year. The islands were first inhabited in 1830, ruled by the U.S. for 23 years after World War II, and returned to Japan in 1968 after which they were treated administratively as a new village. As oceanic islands, they are poor in flora and fauna compared with continental or mainland areas, lacking big mammals, snakes, frogs and Fagaceous trees, while the endemic ratio is high in many groups. The islands are called “the Oriental Galapagos.” The vegetation is classified into seven types according to habitat, physiognomy and dominant species. A pine wood nematode invaded the islands killing many pine trees in the early 1980s. A large typhoon hit the islands and did much damage to the forests in 1983. After this disturbance, Bishofia javanica (introduced sp.) invaded the natural forests rapidly taking the place of native trees. A Bishofia eradication project started in 2002. Feral goats which destroyed the forests of the Mukojima group were completely removed recently to restore the vegetation. Some critically endangered species were bred artificially and transplanted to the original habitats, but regeneration by itself has not been successful. An airport construction plan which was proposed by the Tokyo Metropolitan Government in 1989 was finally withdrawn in 2001.