The world’s largest raised coral atoll, Aldabra Island is one of the UNESCO World Heritage Sites. The island is known to have a volcanic origin. Tourists can spot numerous bird and animal species on the island. These include tiger sharks, manta rays, white-throated Aldabra rail (the only flightless bird in the Indian Ocean), dimorphic egrets, Aldabra sacred ibis, Malagasy Kestrel, and giant land tortoises.
Historically, the name Aldabra was Al-Hadra or Al-Khadra (with several variants), given by Arab seafarers for "the atoll’s harsh, sun-baked environment"; this name was included in the Portuguese maps of the 16th century. They had named the Indian Ocean as Bahr-el Zanj. It was visited by Portuguese navigators in 1511. The islands were already known to the Persians and Arabs, from whom they got their name. In the middle of the 18th century, the atoll became a dependency of the French colony of Réunion, from where expeditions were made for the capture of the Aldabra giant tortoises. As there are no surface freshwater sources on Aldabra, the interests of the explorers (no proof of any explorer's visit prior to 1742) were only to exploit the species of tortoise, turtle, and fish, and not to inhabit the atoll.
Aldabra atoll is in the most southwesterly part of Seychelles and is closer to the coast of Africa 630 km (390 mi) than to Mahé. It is 407 km (253 mi) northwest of Madagascar and 440 km (270 mi) from Moroni on the Comoro Islands. The atoll is the largest raised coral reef in the world with an elevation of 8 meters (26 ft); and the second-largest atoll in the world after Kiritimati Atoll.
The Aldabras were once rich in guano (deposits formed from bird droppings), but it was almost all collected and sold for fertilizer in the early 1950s. South Island is famous for its giant tortoises, and a nature reserve established in 1976 completely protects them and other animals. The Aldabras were designated a World Heritage Site in 1982. The islands were uninhabited in the late 20th century.
The main ecological features of the atoll include its prolific unspoiled coral reefs, lagoon, sea-grass beds, and mangrove mudflats; and the scrubby dry vegetation characteristic of the islands. It is recognized by Birdlife International as an Important Bird Area and is home to the last of the western Indian Ocean flightless birds, the Aldabra rail (all the others have gone the way of the Dodo, driven to extinction).
