The Forestry Agency said Wednesday the Ogasawara Islands' forest ecosystem reserve will be expanded, a move meant to have the island chain registered as a natural World Heritage site, officials said.

The forest ecosystem reserve currently covers 503 hectares in the Haha islands, a group in the chain about 1,000 km south of Tokyo. The designation carries stronger forest management and preservation measures than in other areas.

The agency plans to expand the reserve to other islands and set up a panel of experts next month to determine candidate areas by around August, the officials said.

The Ogasawara chain consists of some 30 islands with a total forest area of 7,000 hectares, of which 6,200 hectares are government-owned.

The subtropical chain features a broad variety of indigenous animals and plants. Some indigenous plants, however, are being eroded by alien species.

The Environment Ministry and Forestry Agency plan to recommend the chain as a candidate for a natural World Heritage site, aiming for 2009 U.N. registration.