The territory, known as Okino-Torishima, has been claimed by Japan since 1931 and represents the southernmost point of metropolitan Tokyo. It consists of a pear-shaped coral reef three miles long and a
mile wide which is almost completely covered at high tide. As an island it would bring with it rights to an Exclusive Economic Zone in a 200-mile radius, an area bigger than the landmass of Japan. But two years ago Chinese ships appeared in the area and said that Okino-Torishima was simply a rock and brought with it no rights.
According to the United Nations Convention on the Law of the Sea, only naturally occurring islands carry economic exploitation rights.
Warming seas and nibbling fish are eroding the remaining reef faster than ever. So Japanese scientists will begin by harvesting about 300,000 eggs of three varieties of coral from Okino-Torishima next month. They will be reared in warm, less turbulent seas off the southwestern island of Okinawa.
Next summer the coral fronds, by then 3cm (1.2in) long, will be planted back on to the reef in Okino-Torishima. It is hard to say that growing coral will directly result in our holding on to our
territory, Toru Noda, of the Ministry for Land, Infrastructure and Transport, said. But it should help to preserve the island. The Tokyo Government has already installed a large sign bearing the official address of the island.
Last year Shintaro Ishihara, the nationalist Governor of the city, was photographed kissing its dwindling earth. The problem is Article 121 of Part VIII of the UN Convention: Rocks which cannot sustain human habitation or economic life of their own shall have no exclusive economic zone or continental shelf. Even Mr Ishihara would balk at living on Okino-Torishima, although there is talk of setting up an electricity plant to establish economic life.
Japan has disputes over islands with each of its near neighbours. To the north it claims the Kurile Islands, seized by the Soviet Union after Japans surrender in 1945. To the west Japan and South Korea claim tiny islands known as Tokto and Takeshima. The most serious
disputes are with China, especially over five islets controlled by Japan as the Senkaku islands, but claimed by China and Taiwan as Diaoyutai. Their ownership is crucial to a dispute over rights to natural gas resources beneath the East China Sea