Үнді мұхитындағы Алдабра атоллының тарихы

Coral atoll in the Indian Ocean

Aldabra is the world's second largest coral atoll, 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. In 1888, the first settlement was established after the Concession was granted by the Seychelles authorities. 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 even 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. 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." 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. 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 Gionnetisland0.480.290.100.050.007MalabarMiddleisland2650.5052.52.0017.700.008VerteÎle 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 Moustiquesisland29.303.100.90.40.0018EuphratesÎle 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

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",

Aldabra sits in the path of the Indian Ocean's westward flowing South Equatorial Current. Eddies are generated in the wake of Aldabra as the South Equatorial Current passes it, driving upwelling of deep waters that bring nutrients to the surface, and drive phytoplankton growth.

The earliest study of the flora and fauna, and also the geomorphological structure was in 1910. There are 307 species of animals and plants on Aldabra. Reptiles are the prominent terrestrial fauna. Tortoise size varies substantially across the atoll, but adult tortoises typically have a carapace length of and can weigh up to They are herbivores and feed on plants, trees and algae that grows in the freshwater pools. The tortoises mate between February and May, the females then lay their eggs from June to September in areas with suitable soil layers. They lay eggs the size of golf balls in a clutch of three to five eggs every few years in high density areas and 14 16 eggs in low density areas. The females can lay several clutches in a year and the incubation period is 73–160 days. The small vulnerable juveniles are prey to coconut crabs, land crabs, rats and birds. In the past giant tortoises have been relocated to other islands in Seychelles and also to Victoria Botanical Gardens in Mahé. One of the longest lived Aldabra giant tortoises was Adwaita, a male who died at the age of about 250 years at Kolkata's Alipore Zoological Gardens on 24 March 2006. Aldabra is a breeding ground for the hawksbill sea turtle (Eretmochelys imbricata) and green sea turtle (Chelonia mydas). Aldabra has one of the largest populations of nesting green turtles in the Western Indian Ocean. Aldabra has a large population of the world's largest terrestrial arthropod, the coconut crab (Birgus latro); and hosts the white throated rail, the only surviving flightless rail species in the Indian Ocean. Sharks, manta rays, and barracuda populate the seas surrounding the island. During the Pleistocene the dominant land predator was the crocodilian Aldabrachampsus which is now extinct. Three extant species of lizards occur, the skink Cryptoblepharus boutonii and the geckos Phelsuma abbotti and Hemidactylus mercatorius. Pleistocene fossils also indicate the former presence of an Oplurus iguana and other skink and gecko species. There are three endemic species of bat from Aldabra: Paratriaenops pauliani, Chaerephon pusilla and the Aldabra flying fox (Pteropus aldabrensis), as well as the more widely distributed Mauritian tomb bat (Taphozous mauritianus). There are 1,000 species of insects, many of them endemic. At least 13 species of cetaceans, including dolphins, orcas, and especially humpback whales, have been identified in the waters. Dugongs, thought to be regionally extinct in the 18th century, have been confirmed multiple times in recent years.

Conservationists feared a major threat to the atoll's biodiversity in the 1960s when, as part of the British Indian Ocean Territory, the British made plans to set up a military establishment on the atoll. Due to national and international opposition this plan was cancelled in 1967. This incident became known as the 'Aldabra Affair' in England. Invasive alien species such as rats, cats and goats that were introduced in the past threaten the native biodiversity of the atoll. Goats were eradicated from the atoll in 2012 after a long term eradication program. Cats have been removed from all of the islands except Grande Terre Island, which allowed for the reintroduction of the Aldabra rail to Picard Island. Research into a feasibility study to eradicate rats from the atoll has been undertaken. Aldabra was until recently free of introduced birds, but the introduced Foudia madagascariensis that was introduced to Assumption Island now occurs on Aldabra. An eradication program for this bird on both Assumption and Aldabra is almost complete. Due to the limited space of its habitat, extreme weather conditions, epidemic and limited range could also pose serious threats to the entire ecology of the atoll. Most of this pollution originates from the regional fishing industry, although a significant proportion is also transported from southeast Asia through ocean currents. The coral reefs at Aldabra were severely affected by the 2016 El Niño event. Although thermal stress was not exceptionally high (less than 4 Degree Heating Weeks), hard coral cover on Aldabra's seaward facing reefs was reduced by over 50% (35% in the lagoon), and soft coral cover fell by over 90%. Fortunately, there are some signs of recovery, as the abundance of juvenile corals has since increased significantly, particularly within the lagoon, although Aldabra's reefs of course remain critically threatened by climate change.

Aldabra atoll was designated a UNESCO World Heritage Site on 19 November 1982. It is one of the two UNESCO World Heritage Sites in the Seychelles;, and is managed by the Seychelles Islands Foundation (SIF). The marine protected area extends into the sea to ensure preservation of its marine fauna. BirdLife International declared Aldabra as an Important Endemic Bird Area (IBA) in 2001 due to its large seabird colonies under categories A1, A2, A4i, A4ii and A4iii, covering an area of overlapping with the special reserve area of of Aldabra Atoll. Aldabra became a Ramsar Wetland Site of International Importance in 2010. Covering 25,100 ha (over half the area of the whole atoll) the wetland ecosystem of Aldabra includes the extensive shallow lagoon inside the atoll, which is carpeted with lush seagrass beds and patchy coral reefs, the intertidal mud flats, the coral reefs outside the lagoon, freshwater pools, beaches, and 2000 ha of mangrove stands. These wetlands support several endangered species including the increasing number of turtles at the atoll, dugongs and many other bird, fish and invertebrate species. Aldabra was designated as a site under the Indian Ocean South East Asia (IOSEA) turtle network, in their 2014 convention.

A small scientific research station of the SIF is based in La Gigi village on Picard Island. The permanent staff (currently 12) conduct research to study Aldabra's biodiversity.

Aldabra is not easily accessed. No airstrips, helipads or landing jetties have been permitted on the atoll. The nearest airfield is on Assumption is south east of Picard Island. Bi monthly supply ships operating from Mahé provide essentials to the research station.

Cruises are operated by several companies along with dive boats which may visit the atoll on expedition tours. Visits to the island by people other than the scientists and staff of the SIF are strictly controlled and only guided tours are provided with prior permission. as of 2012, a yearly average of 900 tourists visit the atoll. Within the atoll, paved walking paths exist from the village of La Gigi, which leads to a promontory from where scenic views of the large lagoon (during low tides) and the mangrove species are seen.