The varied relief has resulted in several distinct climatic regimes, with the prevailing south-east trade winds depositing moisture in the form of rainfall over the central and highest part of the island. A significant feature of Mauritian climatology, however, is the occurrence of tropical cyclones during the summer months. Almost 300 endemic species have been identified, of which the most famous was the Dodo, a large flightless bird now extinct. Permanent human settlement started in the fifteenth century and, ever since, the environment has come under severe threat as its few precious resources (such as ebony) have been exploited indiscriminately.