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University of Tokyo Botanical Gardens reintroduces endangered species to the Bonin Islands

The Bonin or Ogasawara Islands are oceanic islands in the Pacific Ocean, ca. 1,000 km south of Tokyo. Chichijima and Hahajima are two of the major islands. There are little more than 400 vascular plant species native to the islands and around 150 of these are endemic. According to the Japanese Red List of Plants, two species are recorded as extinct, 45 are critically endangered and 32 are listed as endangered.

In 1983, the Botanical Gardens, University of Tokyo started a project of ex situ conservation of twelve endangered Bonin species, with the aim of reintroducing them to their native sites.

One example is Melastoma tetramerum, which was known only by a single native stock on the island of Chichijima at the start of the project. A few individuals were established in the Botanical Gardens by taking cuttings and by inbreeding seeds from the single native tree. As the native mother stock died out in 1995, further reproduction was made from the seeds collected from the reproduced plants. After a decade, reintroduction has been successful and some 300 individuals now survive on Chichijima.

Rhododendron boninense, endemic to Hahajima is another successful example. At present, as many as 90 species endemic to the Bonin Islands are conserved in the Botanical Gardens and many of them still need help in order to maintain native populations or at least individuals on the islands.

BGCI (2005) Cuttings, Vol.2(1) 8