The vegetation of Aldabra, except for the area around the settlement and a number of Casuarina groves, is probably in approximately its original condition. It is mostly a varied evergreen or semi- deciduous scrub or scrub-forest, with open areas of grass or sedge meadow and ephemeral vegetation. Many local cover types can be distinguished according to the I.B.P.-Fosberg classification. The total flora will come to about 200 species, of which 47 are thought to be exotics. O f these, only Casuarina equisetifolia presents a serious threat to the native vegetation. In certain areas grazing by tortoises exerts a conspicuous influence on the physiognomy of the vegetation. Mangroves line the lagoon shores in many places. Meadows of 'sea-grasses’ cover much of the coral reef surrounding the atoll.