It was established by the British government on 1 April 2010 as a massive, contiguous, marine reserve, it encompasses 640,000 square kilometres (250,000 sq mi) of ocean waters, including roughly 70 small islands and seven atolls of the Chagos Archipelago.
The establishment of the protected area was immediately controversial, as the Chagossian people were forcibly expelled from the archipelago, including the outlying islands, because the United States wanted a military base on Diego Garcia; their expulsion has been described as ethnic cleansing.
[19] From 10 November 2009 to 5 March 2010, a public consultation was carried out by the UK government to take views on whether or not a marine protected area (MPA) should be established in the archipelago.
In the final months leading up to the designation, the Bertarelli Foundation offered to fill the funding gap left by the absence of fisheries income and thereby contribute to the costs of an enforcement boat for a period of five years.
[27] One of the most unusual aspects of the Chagos marine environment is its extremely healthy and diverse coral cover, which is dense even in deep water and on the steep outer slopes of reefs.
[13] The archipelago harbours eighteen different species of breeding birds and ten of its islands have been designated as Important Bird Areas (IBAs) by Birdlife International, making the region the most diverse breeding seabird community in this tropical region,[37] though the presence of human-introduced rats on several of the other islands severely hinder seabird nesting on these.
[13] Due to the long distances which the larvae of the coconut crab can travel, the Chagos population is considered important in replenishing numbers in other areas of the Indian Ocean.
The Independent also revealed that American ships have been pouring waste including treated human sewage for three decades into the lagoon on Diego Garcia, which has served as a key strategic base for the US since the 1970s.
Mauritius considers that the UK, not being a "coastal State" under UNCLOS and international law, had no authority to purport to establish a marine protected area around the Chagos Archipelago and that the MPA was not compatible with the rights of the Chagossians.
[43] In a letter to Greenpeace, the Mauritian Lalit de Klas political party said "The British government's plan for a marine protected area is a grotesquely transparent ruse designed to perpetuate the banning of the people of Mauritius and Chagos from part of their own country," In 2012, Greenpeace ship SY Rainbow Warrior was in the Indian Ocean region and the government of Mauritius initially blocked it from making a scheduled stopover at Port-Louis harbour.
The reason for the refusal was the unconditional support that Greenpeace has given the British authorities in the controversial project of a protected marine park in the Chagos archipelago.
Mauritius insisted that Greenpeace, which claims to be fighting for environmental protection, showed a hypocritical attitude by remaining silent over the proposed construction of a marine park.
[44][45] Thus, in official correspondence, Greenpeace International said at the outset that: our support for the Marine Protected Area was, and remains, subject to the clear proviso that it should be without prejudice to the rights of the Chagossians or the sovereignty claim of Mauritius.
[44][45]On 1 December 2010, WikiLeaks released a leaked US Embassy London diplomatic cable dating back to 2009 exposing British and US calculations in creating the marine nature reserve.
Richard Mills concludes: Establishing a marine reserve might, indeed, as the FCO's Roberts stated, be the most effective long-term way to prevent any of the Chagos Islands' former inhabitants or their descendants from resettling in the British Indian Ocean Territory.
[3]The cable[3][46] which records Roberts' assertion that the marine reserve was proposed by the Pew Charitable Trust, was classified as confidential and "no foreigners", and leaked as part of the Cablegate cache.
He qualified the ruling as an important milestone in the relentless struggle, at the political, diplomatic and other levels, of successive Governments over the years for the effective exercise by Mauritius of its sovereignty over the Chagos Archipelago.
[49] Even though the rights to the archipelago are disputed,[50] the sovereignty of Chagos clearly rests with the UK, who have complete control of access to and withdrawal of resources from the islands.