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British Indian Ocean Territory
(Chagos Archipelago)

The Chagos Archipelago, which is claimed by the United Kingdom as the British Indian Ocean Territory (BIOT) lies about 1,770km east of Mahé (the main island of the Seychelles). It consists of about 60 low-lying coral islands, and covers some 640,000 sq km of ocean. The total land area is only about 60 sq km. Diego Garcia, the largest and most southerly island, is 44 sq km in land area. It houses a joint UK/US Military base.

Mauritius is not opposed to the base remaining on Diego Garcia and the US does not object to Chagossian resettlement. Mauritius has said that it is content to allow the US military base to remain on Diego Garcia as and when it achieves sovereignty over the Chagos Archipelago.

The Archipelago had been part of Mauritius’ territory since at least the eighteenth century, when France governed it. The entire territory had been ceded to the United Kingdom in 1810 and kept intact until what the Archipelago’s excision on 8 November 1965. For the last 40 years the islands have been uninhabited except for the southernmost atoll of Diego Garcia, the western arm of which contains the military facility and at least 1000 Asian contractors and others. That facility does not depend on local food resources but is provisioned and supported entirely from outside the archipelago.

The archipelago forms the British Indian Ocean Territory (BIOT), created in 1965 for UK and USA defence purposes. It is a large group of atolls and submerged banks in the central Indian Ocean, lying at the southernmost end of the Lakshadweep–Maldives–Chagos ridge. Its central 200 × 300 km area contains five atolls with islands, one atoll which is awash at high tide, and a dozen more which are submerged to depths of 6–25 m. The Great Chagos Bank is the world’s largest atoll in area, although it contains only eight islands on its western and northern rim. The area within the total BIOT 200 nm zone is about 550 000 km2.

Diego Garcia contains half the total land area, the rest being split among over 50 small islands, the number varying to some degree with tidal height and shifts of sand banks. All islands are very low lying, and are typical coral cays constructed of limestone. Beneath these lie freshwater lenses sustained by high rainfall.

BIOT is a UK Overseas Territory and as such has its own government, which in this case is the office of the BIOT Administration located in the UK Foreign and Commonwealth Office in London. The senior UK military officer in the archipelago is the British Representative of the Commissioner.

Severe warming in 1998 then caused severe mortality on all Chagos reefs as it did throughout the Indian Ocean. Coral and soft coral mortality was almost total on several Chagos ocean-facing reefs to clearly defined depths, below which corals provided much higher cover. This killed zone extended deeper in southern atolls, and in Diego Garcia for example was greater than 40 m depth, while in more northern atolls it extended to only about 10–15 m depth. Such variability was mirrored in the Indian Ocean as a whole. Increase in coral cover became evident by 2006, especially in shallow water where restoration to pre-1998 levels occurred by 2010. Deeper recovery has been slower.

The outstanding ecological values of the Chagos Archipelago led in 2010 to the creation of the world’s largest marine protected area (MPA), and which became fully a no-take MPA later the same year. Over the period of BIOT’s existence, there have been a dozen scientific visits, involving more than 50 visiting scientists. It has become clear during this period when coral reefs in most of the Indian Ocean have become seriously degraded that those of Chagos persist in an exceptionally good state. This led increasingly to calls to extend its conservation, and data to support the concept came from over 200 papers arising from both those scientific expeditions and, to a lesser extent, from unpublished information, from regional data and from modelling.

A Marine Protected Area (MPA) introduced by the British Government around the Chagos Archipelago (apart from Diego Garcia, where there is a US military base) in 2010 was ruled unlawful in 2015 by a Tribunal under the UN Convention on the Law of the Sea. Many people have suggested, incorrectly, that the Chagos marine preserve zone, which was initiated in 2010, was deliberately put in place to prevent the Chagossians returning to the British Indian Ocean Territory. The Mauritian Government was unwilling to address the issue of the MPA in isolation from that of the sovereignty of the BIOT.

The United Kingdom had held three substantive rounds of talks with Mauritius since September 2016, but had not been able to bridge their differences. During those talks, the United Kingdom’s offers had clearly signalled acknowledgement of Mauritius’ long-term interest in the Archipelago, offering a framework for the joint management of all the Territory’s islands except Diego Garcia. Strategic and tactical forms of bilateral security cooperation had also been offered.

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Page last modified: 31-07-2017 18:35:09 ZULU