Nature of Ogasawara

The Ogasawara Islands are relatively warm throughout the year (average temperature of 23℃) and are under a subtropical climate zone. The annual temperature range is quite wide at about 10℃ compared to other subtropical islands such as the Mariana Islands and Hawaiian Islands. With annual precipitation at 1,280 mm, there is not much rainfall in general.

Within Japan, Yakushima, Amami Oshima, and Okinawa Islands are subtropical as well, but they are continental islands (being connected to the continent) while the Ogasawara Islands are oceanic islands (having never been connected to the continent), thus each ecosystem of the islands is quite different.
Animals and plants of the Ogasawara Islands have accidentally reached the islands by being carried by birds, attached to driftwood, flown in by the wind, or washed in by the current, and only those that are suited to the island’s environment have survived and evolved in a unique manner over time, eventually becoming endemic species.
Land snails and plants, especially, show ongoing evolutionary processes, and their processes of speciation are well preserved. Thus the Ogasawara Islands are said to be a “laboratory of evolution,” and this is the reason the islands were designated as a Natural World Heritage site in 2011.

Terrestrial Species

The Ogasawara Islands are habitats of many globally important endangered species such as the short-tailed albatross, and they are also essential for the conservation of biodiversity of the central marine region of the Pacific Ocean.

Marine Species

The surrounding deep-blue ocean of the Ogasawara Islands is called “Bonin Blue,” and various underwater landscapes such as coral reefs and various tropical fish spread out under the “Bonin Blue” ocean.

A variety of marine species can be seen around the Ogasawara Islands, including dolphins and whales, and the islands are the largest breeding ground for green sea turtles in Japan as well. Research on fishes found in Ogasawara is not advanced compared to that on terrestrial species, but freshwater fish Rhinogobius ogasawaraensis, banded parrotfish, spotted angelfish, and Ammodytoides kimurai of marine fish are thought to be endemic. In Ogasawara, there are also fishes showing geographical differences such as the Pacific drummer and Clark’s anemonefish.