The turtles and exiles sharing an island hell

Ascension Island, in the middle of the Atlantic Ocean 800 miles distant from St Helena, is the subject of this book and the nesting place from January until June for thousands of green turtles ( Chelonia mydas ). It was, until recently, a "closed island": military flights are still the only way to get there, and tourism has been launched only recently.

Sergio Ghione, an Italian doctor and research scientist, visited Ascension Island in 1997 to research the turtles' "natal homing instinct". Struck by the lunar-like landscape, he eloquently describes the feeling of isolation peculiar to Ascension. And as early as the 17th-century, a shipwrecked sailor wrote: "Anybody would have believed that the Devil himself had moved his quarters and was coming to keep Hell in Ascension."

Ghione is an island enthusiast. He waxes lyrical about his boyhood fascination with these "magical places" and their utopian potential. He is at his best when describing the history and volcanic provenance of the world's islands: St Matthews, the phantom island; Graham's Bank, the island that almost was; and Lahtayikee, formed as recently as 1996.

Ascension, which erupted into existence about 600 years ago, was discovered by the Portuguese in 1501. But it was only when Napoleon was exiled to St Helena and the British claimed Ascension that the island gained strategic importance. It went on to become a crucial "node" in both world wars, the cold war and the Falklands war. The 1960s saw the building of a Nasa base, crucial to the Apollo missions but now defunct.

Ghione describes all this in a laconic and conversational style. He seamlessly weaves the historical with the geographical, and his descriptions are often pleasingly tangential, melding descriptions of the island's past and present inhabitants with observations on its ecological make-up (the green sand, the world's worst golf course). He has an eye for the curiosities of island life - the single grocery shop that sells Christmas goods year round, the ritual of throwing paint at a particular kerbstone - and the Britishness of this oddest of colonies. There is a rigid adherence to "elevenses" and the quintessentially British Exile's Club observes strict licensing laws.

And the turtles? We learn in detail about their nesting habits, the trials and tribulations of attaching transmitters to their shells, and in the final chapter Ghione relates the most likely hypothesis for their remarkable ability to navigate across the Atlantic to Brazil and back.

The human inhabitants are almost as extraordinary. There is no indigenous population. As Ghione puts it: "Everyone is just passing throughI There is no memory of history and there are no old people." An appropriate place, perhaps, for someone with a distaste for nostalgia.

Anna Thomson is on the staff of The THES .