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1 . Chagos Archipelago (UK)     Chagos Archipelago (UK)
The British Indian Ocean Territory (BIOT) covers a very large area of reefs and islands, also known as the Chagos Archipelago. There are some 50 islands and islets and, although the total land area is only 60 square kilometers, there is a vast area of reefs. These include four true atolls (Diego Garcia, Egmont, Peros Banhos and Salomon), a mostly submerged atoll (Great Chagos Bank, the largest atoll structure in the world at some 13 000 square kilometers), and a number of submerged banks (including Speakers Bank, Blenheim Reef, Pitt Bank and Centurion Bank). The southernmost atoll, Diego Garcia, is unusual in having a narrow but continuous land rim extending around 90 percent of the atoll’s circumference. The northerly atolls, by contrast, have only small islands scattered around them. As with the Maldives, the Chagos Archipelago has grown up over the volcanic trace of the Réunion hotspot, and forms the newest and southernmost extension of the Chagos- Laccadive Ridge. The reefs and islands are highly isolated – the nearest reef structures are those of the Maldives, some 500 kilometers to the north, while the nearest continental land mass is that of Sri Lanka, more than 1 500 kilometers away.

A number of the islands in the Chagos Archipelago, inhabited from the late 18th century, were transformed by the development of coconut plantations and the introduction of rats and other animals. However, it is unlikely that this had a major influence on the marine environment as there was no major export fishery. There was a forced evacuation of the islands in the early 1970s when the military base on the southernmost island of Diego Garcia was established. This has some 3 000 personnel and large vessels permanently at anchor in the lagoon. The impacts of this base have included dredging in the lagoon and some mining of the reef flat, as well as a substantial recreational fishery. There are, however, strict environmental controls on many activities. Personnel are not permitted to dive, and snorkelling is also forbidden on the outer reef slopes. The remaining islands are now uninhabited, although there are a number of visiting yachts and other vessels (commercial tourist-carrying vessels are not permitted). These may be causing localized impacts through anchor damage and sewage pollution, notably in the enclosed lagoon of Salomon Atoll.

There is a large offshore tuna fishery as well as a small licensed inshore fishery operated by Mauritian fishermen who visit the reefs for a few months each year. There have also been reports of illegal fishing, notably for sharks and sea cucumbers, although the BIOT Administration has run a fisheries protection vessel for part or all of the year over recent years. A number of the islands and their associated reefs have been declared protected areas. These cover substantial areas of reef, but there is no active management of these sites and the licensed fishing vessels are allowed to operate within them. Overall, partly as a result of their history and continuing isolation, but further supported by current management measures, the reefs of the Chagos probably represent some of the most pristine and best protected in the Indian Ocean.
Source: Spalding, M.D., C. Ravilious and E.P. Green , 2001 , World Atlas of Coral Reefs . Prepared at the UNEP World Conservation Monitoring Centre. University of California Press,Berkeley,USA.421p. (See Document)

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