The species of the archipelago of New Caledonia are relicts of a type of vegetation which earlier covered much of the tropics of the Earth, including much of the mainland of Australia, South America, Antarctica, South Africa, and North America. Although tropical cloud forests disappeared during the glaciations, they re-colonized large areas during successive geological eras when the weather was favorable again. At other times they were replaced by more cold-tolerant or drought-tolerant sclerophyll plant communities. Many of the then existing species became extinct because they could not cross the barriers posed by new oceans, mountains and deserts, but others found refuge as species relict in coastal areas and islands.