9 - Biogeography and conservation of the flora of New Caledonia

Summary

Geography

Straddling the Tropic of Capricorn, New Caledonia is situated in the South Pacific Ocean between latitudes 18° 00′ and 23° 50′ S, and longitudes 154° 45′ and 176° 20′ E. It is an archipelago made up of the islands of Grande Terre, Iles Belep, d’Entrecasteaux Récifs, Île des Pins, the Loyalty Islands and several other small islands such as the Chesterfield Islands and Walpole Island (Fig. 9.1). New Caledonia is an isolated archipelago situated some 1500 km east of Australia with the nearest land further to the east at the New Hebrides Islands and Fiji. New Caledonia is one of the extant land masses of an ancient continent known as Zealandia and now almost completely submerged. The island was formerly part of Australasia but separated from it about 60–80 million years ago (Ma) and drifted to its present position by about 50 Ma. It is, therefore, one of the most important and isolated surviving fragments of Gondwanaland. In the process, much or all of the area of New Caledonia appears to have been submerged for up to 20 Ma. During this period, oceanic mantle was deposited over the original schistic rock, eventually forming a thick layer of ultrabasic substrates including peridotite, ferricrete, serpentinite and laterite. These were once widespread over the islands and still cover about 30% of the land surface.