Aldabra, the world's second-largest coral atoll (the largest is Kiritimati), is located east of the continent of Africa. It is part of the Aldabra Group of islands in the Indian Ocean that are part of the Outer Islands of the Seychelles, with a distance of 1,120 km (700 mi) southwest of the capital, Victoria on Mahé Island.
History
The name Aldabra, originally Al-Hadra or Al-Khadra (with several variants), was given by Arab seafarers for "the atoll's harsh, sun-baked environment"; this name was included in the Portuguese maps of the 16th century. The islands were already known to the Persians and Arabs, from whom they got their name. They had named the Indian Ocean as Bahr-el zanj. It was visited by Portuguese navigators in 1511. 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 European explorer's visit prior to 1742) was only to exploit the species of tortoise, turtle and fish, and not to inhabit the atoll. In 1810, with Mauritius, Réunion, the Seychelles and other islands, Aldabra passed into the possession of Great Britain. Réunion was later 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.
Admiral W. J. L. Wharton of the British Navy landed in Aldabra in 1878 to conduct hydrographic surveys of the islands.Aldabra from Ministry of environment website In 1888, the first settlement was established after the Concession was granted by the Seychelles authorities. The intention was to exploit and export the natural resources of the islands. The villagers built a chapel, in the middle of the badamier trees, using timber and steel; the chapel was considered an essential addition to the plantation houses and office buildings. As Aldabra had no freshwater resources, large rectangular-shaped water storage structures were built adjoining each building. A two-roomed jail was also built in the village, a remnant of which is extant.
The exploitation of tortoises for commercial purposes at that time is illustrated by the remnants of a crushing mill at Picard Island, which was used to crush bones of tortoises, which were also brought in from other islands in the atoll. Efforts made to grow plantation crops of coconuts, cotton, and sisal failed due to inadequate water sources on the atoll; relics of these plantations are still found on some of the islands. In the late 19th century, goats were introduced as a food source for the villagers (about 200) living there. Ship rats were inadvertently introduced and recorded before 1870, and house geckos were noted from the 1970s. Sailors landed on the atoll in the 19th century and captured 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.Carpin, Sarah,(1998) Seychelles, Odyssey Guides, p.162, The Guidebook Company Ltd., Accessed 22 June 2008
In the early 1800s, concessions given to individuals almost destroyed the forests and tortoise habitats in many islands in Seychelles; on Aldabra Atoll, in view of its remoteness and rugged topography, only small areas of forests were cleared for agricultural operations (mostly coconut plantations) but the tortoises were intensely captured for meat and trade. However, James Spurs, who had the concession of the atoll, was responsible initially for saving the tortoises on the atoll when he banned killing them in 1891.
Following World War II, exploitation of Aldabra for commercial use came to an end and restrictions were imposed on the number of people who could stay on the islands; this number was fixed at 200 at a time. Introduction of invasive species was banned, faunal species were protected under law, and active research on the ecology and biodiversity of the atoll was undertaken by the Royal Society of London from the mid-1970s.
Aldabra, along with Desroches and Farquhar, was part of the British Indian Ocean Territory from 1965 until Seychelles' independence in 1976. In the 1960s, as a part of their "Ocean Island Policy", and to support East of Suez commitments, the British government considered establishing an RAF base on the island and invited the United States to help fund the project in return for shared use of the facility and a settlement of 11 million dollars. Simultaneously (mid-1960s), the British Broadcasting Corporation became interested in Aldabra as a possible transmitter site, to broadcast the BBC Overseas Service (BBC) into the African mainland. The BBC mounted a fact-finding expedition (Expedition Turtle) to assess its suitability for this purpose. The BBC relied on the RAF for developing the atoll as without this their project would not have been feasible.
After an international protest by scientists, known as the "Aldabra Affair", however, the military plans were abandoned and the atoll instead received full protection. The "Environmental lobbyists" under the leadership of Julian Huxley, with the support of MPs Tam Dalyell and Robin Cook, got the British venture torpedoed. In 1966, British Defence Minister Denis Healey had observed: "As I understand it, the island of Aldabra is inhabited – like Her Majesty's Opposition Front bench – by giant turtles, frigate birds and boobies."
Subsequent to the thwarting of plans to establish a military station at Aldabra (which instead focused on Diego Garcia in the Chagos Islands), the Royal Society of London resumed their scientific study of the flora and fauna of the atoll with Professor David Stoddart as the leader. The Royal Society bought the lease of the atoll in 1970 and their research station became functional from 1970. After completion of their assigned work, the Royal Society left and the Seychelles Islands Foundation (SIF), a public trust of Seychelles, assumed management and protection of the atoll in 1979. SIF functions under the patronage of the President of Seychelles and Aldabra was declared a Special Nature Reserve in 1981; it became a UNESCO World Heritage Site on 19 November 1982. A brass plaque inscribed with the citation "Aldabra, wonder of nature given to humanity by the people of the Republic of Seychelles" was erected on the atoll. This appreciation befits the atoll which is truly one of the greatest ecologically undisturbed raised coral atolls in the world.
Geography Aldabra atoll is in the most southwesterly part of the Seychelles, and is closer to the coast of Africa than to Mahé. It is northwest of Madagascar and from Moroni on the Comoro Islands. The atoll is the largest raised coral reef in the world with an elevation of ; and the second-largest atoll in the world after Kiritimati Atoll. It lies at and belongs to the Aldabra Group, one of the island groups of the Outer Islands of the Seychelles, which includes the island of Assumption and the atolls of Astove and Cosmoledo.Carpin, Sarah,(1998) Seychelles, Odyssey Guides, p. 161, The Guidebook Company Limited, Accessed 22 June 2008 Aldabra atoll is long (in east–west direction) and wide. It has a large shallow lagoon, in area, which is about two-thirds dry during low tide. The lagoon is encircled by fringing coral reef.
Around the rim of the lagoon are the larger islands of the atoll. The total land area of the atoll is . The size including the lagoon is . The outside rim of the atoll has three passages which connect to the lagoon, which is in width where it opens to the sea. The water depth in the lagoon averages about ; however, the passages that open to the sea are up to deep and strongly affected by tidal currents.
List of islands Aldabra atoll has, besides the four larger islands, some 40 smaller islands and rocks,List from constitution all inside the lagoon, as well as a few very small islets at the West Channels between Grand Terre Island and Picard Islands, the largest of those being Îlot Magnan. Îlot Magnan .
IslandSobriquettypeLocationArea(hectares)Coastline (km)Length (km)Width (km)Elevation (m)1PicardWestisland928.7025.803.203.900.002Polymnieisland193.6010.401.013.420.003North Niçois Îlot Niçois Nordisland2.800.940.380.090.004South Niçois Îlot Niçois Sudisland0.730.350.130.060.005GrosGros ÎIot Gionnetisland4.001.080.400.120.006PetitePetite ÎIot Gionnetisland0.480.290.100.050.007MalabarMalabar the only island that has buildings other than PicardMiddleisland2650.5052.52.0017.700.008VerteÎle Verteisland4.151.500.430.120.009MarquoixÎlot Marquoixisland1.620.880.250.110.0010North Coconutisland52.304.400.90.70.0011South Coconutisland58.104.261.10.60.0012MichaelÎle Michelisland37.005.571.450.440.0013Petit MentorPetit Mentor Endansisland0.100.100.030.030.0014GrosGros ÎIot Sésameisland2.350.930.360.070.0015PetitPetit ÎIot Sésameisland0.200.200.060.040.0016Grand TerreSouthisland11400106.6534.108.500.0017MoustiquesÎle Moustiquesisland29.303.100.90.40.0018EuphratesInfo on the islands Île Espritisland36.102.771.050.50.0019Sylvestre Westisland0.400.300.050.10.0020Sylvestre Eastisland0.200.200.050.040.0021Chalenisland0.350.500.180.10.0022Grabeauisland1.240.000.000.000.0022Grande MagnanÎlot Grande Magnanisland5.150.000.000.000.0022Petite MagnanÎlot Petite Magnanisland2.360.000.000.000.0022Lanierisland1.030.000.000.000.0022Duboisisland2.730.000.000.000.0022Yangueisland1.650.000.000.000.0022Emileisland5.050.000.000.000.00 Aldabra AtollAtoll15520.00 16 More Islands (unspecified location, but sizes are included under "Other Islands":
Île aux Cendres Îlot Parc Champignon des Os Grand Mentor Grand ÎIot Heron Rock Hide Island Île aux Aigrettes Île aux Cèdres Îles Chalands Île Fangame Île Héron Île Suacco Îlot Déder Îlot du Sud Îlot du Milieu Îlot du Nord Îlot Macoa Îlot Salade Middle Row Island Nobby Rock North Row Island Petit Mentor Petits ÎIots Pink Rock South Row Island Table Ronde
Geology The atoll reflects both fossil and geomorphological features, the former is the source of the biodiversity seen today. The atoll consists of reef limestone of Pleistocene age (with irregular coral formations called "champignon", made up of two layers of varying stages of crystallization) and this extends over an average width of rising to a height of above sea level, and forming the rim line (low cliffs with "deep notches, preceded by jagged pinnacles") of the shallow central lagoon. Geologically the limestone beds have been subjected to striation, sink holes and pits with prominent and continuous limestone bed on the eastern side above the sediment deposits.
The coastline has undercut limestone cliffs above a perched beach; it is in two clear terraces of and height above sea level. While the terrestrial topography (spread over an elevation range of ) is rugged and dictated by the geomorphic conditions, the land surface comprises limestone of about 125,000 years age, which has uplifted many times above the sea level. The surface conditions are criss-crossed and riddled with pot holes and pits. In the eastern zone of the lagoon, though the surface is continuous, sediment beds are also seen. The windward southern coast is made up of sand dunes.
Climate and tides Aldabra is situated in the dry zone of the south-west Indian Ocean. The northwest monsoon season is from November to March and brings the heaviest rainfall. In the remaining months, the south-easterly trade winds are dominant. Aldabra receives an annual average rainfall of . Cyclones are rare in the Seychelles due to its nearness to the Equator. The reported monthly mean maximum air temperature recorded in December is . The mean minimum temperature recorded in August is .