Aldabra Atoll : SEYCHELLES
Aldabra Atoll, 1,150 km southwest of Mahe, is the largest raised coral atoll in the world, encompassing more than a dozen islands bordering a vast lagoon.The atoll’s islands nurture an array of both unique flora and fauna, as well as the world’s largest population of 150,000 giant tortoises. Its lagoon boasts the most vibrant marine life of the entire archipelago. The atoll is comprised of four large coral islands which enclose a shallow lagoon; the group of islands is itself surrounded by a coral reef. Due to difficulties of access and the atoll's isolation, Aldabra has been protected from human influence and thus retains some 152,000 giant tortoises, the world's largest population of this reptile. Aldabra is a raised coral atoll in the Aldabra Group of islands in the Indian Ocean that form part of the Seychelles. The island is more than 700 miles from Mahé and is closer to the coast of Africa and Madagascar.[1] Virtually untouched by humans, with distinctive island fauna, including the Aldabra Giant Tortoise, the island is designated a World Heritage Site. The atoll is home to the world's largest population of giant tortoises, numbering some 100,000 individuals.[2] They are also known for their green turtles, hawksbill turtles, hammerhead sharks, mantarays, barracuda, and birds, including the Aldabra rail, the last surviving flightless bird of the Indian Ocean region. The Aldabra Group includes the island of Assumption and the atolls of Astove and Cosmoledo.
Aldabra was visited by Portuguese navigators in 1511. The islands were already known to the Arabs, from whom they get their name. In the middle of the 18th century, they became dependencies of the French colony of Réunion, from where expeditions were made for the capture of the giant tortoises. In 1810 with Mauritius, Réunion, the Seychelles and other islands, Aldabra passed into the possession of Great Britain. Réunion was returned to France, and Mauritius gained possession of Aldabra as well as the rest of the Seychelles. The previous inhabitants were emigrants from the Seychelles. Sailors landed on the atoll in the 19th century and attempted to raid the island for tortoises as food; in 1842, two ships were reported to have taken 1200 of them. By 1900, the tortoises were nearly extinct and a crew would often have to hunt for three days to find one. Aladabra was designated a World Heritage Site on November 19, 1982, and is administered by the Seychelles Island Foundation based on Mahé. An environmental disaster for the island was averted[citation needed] in the 1960s when the British nearly entered into negotiations with the United States to turn the island into a military air base. The proposal created an international protest by ecologists and their lobbying resulted in military plans abandoned and the wildlife habitat receiving full protection. The abandoned settlement Picard on the southwestern tip of West Island is now home to the Research Officer, Island Manager and their rangers and staff. There is no other permanent population. The islands are managed by the Seychelles Island Foundation.
Aldabra Atoll (924' S, 4620' E) is a large (34 km long, maximum 14.5 km wide , area 155 km2) raised atoll located in the Western Indian Ocean. It is situated 1150 km southwest of Victoria (the capital of the Seychelles on the island of Mahe) and 420 km north of Madagascar. Aldabra has been described as "one of the wonders of the world" by Sir David Attenborough as its isolation in a remote area of the Indian Ocean, combined with an inhospitable terrestrial environment, has helped preserve it in a relatively natural state. Increasing levels of stress from human activities are contributing to the decline of the worlds coral reefs, Aldabra has so far escaped the worst of these stresses and provides an ideal natural laboratory for studying tropical marine ecosystems and related environments (such as seagrass and mangroves). Aldabra is formed from late Quaternary raised reef limestones, averaging 2km in width and up to 8m above sea level, and rimming a shallow central lagoon. The limestone has been eroded over the years to form an dangerous terrain of sharp spiky rocks and numerous pits, making walking off established tracks unadvisable. Many of the pits contain fresh or brackish water that sits on top of surrounding seawater as a lens and rises and falls with the tides. Aldabra has monthly mean maximum (December) and minmum (August) temperatures of 31ºC and 22ºC respectively. Average rainfall, with Aldabra located in the relatively dry zone of the southwest Indian Ocean, is 1100mm per year. Climate is heavily influenced by the NW monsoon winds from November to March bringing the heaviest rainfall, with SE trades blowing throughout the remainder of the year. The lagoon at Aldabra is linked to the ocean by two major and one smaller channels and by several smaller reef passages. Tidal range is 2 to 3 m and results in large exchanges of water between the lagoon and open ocean through the channels. The main channel alone drains approximately 60% of the lagoon. The scientific history of Aldabra encompasses almost 100 years of both terrestrial and marine based investigations. Early contributions regarding the flora and fauna, and indeed geomorphological structure, of Aldabra made it in 1910 one of the better known Indian Ocean reef islands. In the mid 1960s Aldabra was thrust into the international spotlight, being considered by the British Government as a possible air-staging outpost, with the threat of the construction of an airstrip and support facility.
