Diego Garcia is a highly guarded military base of the United States and strategically situated between East Africa, East Asia, and Southeast Asia, making it a vital outpost for basing US naval forces and projecting air and naval power into the region.

In 1966, the United Kingdom signed an agreement with the United States, giving it permission to use the island as a naval base for an initial period of 50 years. This agreement is set to expire in 2016. Unless the UK or the US takes steps to terminate the agreement, it will automatically be extended for a further period of twenty years.1 The expiry of the initial agreement, brought hope for the islanders, who were forced to flee during the period 1967- 1973, and then denied the right to return to their native land.

This issue brief studies the social and environmental impact of military activities on the Chagos Archipelago. It provides a brief history of Diego Garcia and its strategic importance for both the United States and United Kingdom. It examines Mauritius claims over the archipelago and provides an insight to the Chagos Marine Protected Area. The paper also makes recommendations or the way ahead to resolve the highlighted issues.


Brief History and Importance of Diego Garcia

The Chagos Archipelago comprises of seven atolls and more than 60 islands, and Diego Garcia is the largest. It was claimed by the French during the 18th century and used for plantation of coconuts and fishing.  Mauritius and its dependencies – Chagos Archipelago and Seychelles, were ceded to the United Kingdom by France in 1814 through the Treaty of Paris, and thereafter administered by Mauritius. Later, the Archipelago was retained by the United Kingdom, as one of the conditions for Mauritius to attain independence in 1968.

On 30th December 1966, Britain agreed to lease Diego Garcia to the United States for the construction of a naval base.2 Due to its small population, the UK successfully uprooted the island’s people, as well as managed to avoid large-scale controversy.3 The depopulation from 1968 to 1973 was undertaken by intimidation and restricting inward migration. The displaced Chagossians settled mostly in Mauritius and

Diego Garcia is often regarded to be at the core of United States’ strategy in the Indian Ocean. The United States did not entail any monetary liability on account of the lease, but a US $ 14 million ‘discount’ to UK was offered for acquiring the Polaris nuclear missiles. The island is strategically significant for the United States as it is remote, secure and centrally placed. It is relatively immune from land based attack and, due to the absence of a local population; the base has been insulated from local political conflicts over the last five decades.4

The island is home to about 1,700 military personnel and 1,500 civilian contractors with only about 50 British troops. The island is used jointly by the US Navy and the Air Force.5  A   number of air operations during the 1991 Persian Gulf War, 1998 Iraq War, and 2001 strikes in Afghanistan were launched from Diego Garcia.

During the Cold War, Diego Garcia was highly valuable for the United States to monitor the activities of the erstwhile USSR. In Post-Cold War, the base is vital for US security and foreign policy interest such as the war on terror and monitoring of other naval activities in the Indian Ocean Region.


Mauritius claims over the Archipelagos 

Mauritius government has maintained its claim to sovereignty over the Chagos Archipelago, arguing that it was illegally separated from Mauritius, before it gained independence in 1968. Mauritius views the issue as a breach of United Nations resolutions on decolonisation, most notably the United Nations General Assembly Resolution 1514/XV of 14 December 1960, stating:

Immediate steps shall be taken… all other territories which have not yet attained independence, to transfer all powers to the people of those territories, without any condition or reservations…enable them to enjoy complete independence and freedom.”6

The Chagossians have unsuccessfully waged a number of legal battles to resettle on the island since 2000. However, they have achieved a few successes like financial compensations and the right to own a British passport.

The UK also came under criticism after it declared the BIOT as marine reserve, with the exception of Diego Garcia, leading to Mauritius filing a case under the United Nations Convention on the Law of the Sea (UNCLOS).


The issue of Chagos Marine Protected Area – Social and Environmental Impact

In February 2009, the British government announced plans to establish a marine reserve in the BIOT. After numerous protests by Mauritius, the UK initiated a four month public consultation on its decision to establish a Marine Protected Area (MPA) in Chagos. Chagos MPA was declared on 1st April 2010 by the BIOT Commissioner. It is one of the largest ‘No-take’ MPA i.e. prohibition on fishing, dredging, extraction of minerals, construction and dumping.  The MPA covers the entire 200-mile Exclusive Economic Zone (EEZ) around the territorial waters of the Chagos Archipelago, except for Diego Garcia, with the MPA ending 3 nautical miles around the island. 7 This raised several questions including whether it was an excuse to prevent the inhabitants from returning back to their homes or if it was genuinely meant to conserve the local ecology.

The Chagos MPA came under controversy after a diplomatic cable was leaked on 1st December 2010, which stated that the reserve was an outcome of a deliberate plan by the United Kingdom and United States, with an agenda of preventing the indigenous population from returning to their land.

On 20th December 2010, the Mauritian Government commenced litigation proceedings against the UK Government under UNCLOS to challenge the legality of the Chagos MPA. During the proceedings, it was observed that the United Kingdom had violated 1982 UNCLOS provision, which required it to consult the Mauritius prior to establishing the MPA.

The Tribunal found that the UK was bound under international law to:

(a) Return Chagos back to Mauritius, when it was no longer needed for defence purposes.

(b) Preserve the benefits of any minerals or oil discovered in or near the Chagos Archipelago for Mauritius.

(c) Ensure that fishing rights in the Chagos Archipelago would remain available to Mauritius as far as practicable.8

From the United Kingdom’s perspective, the MPA was an effort to protect the flora and fauna of the Chagos archipelago. The US has also been trying to highlight its seriousness in undertaking international environmental responsibilities through the MPA. Their actions may be considered to resemble the concept of “greenwash” that tends to distract attention from the negative aspects of militarism, including instances of environmental degradation, the mistreatment of human subjects, and the perpetuation of colonial forms of government. According to Peter Harris, professor in the University of Texas, “UK clearly believes that it is possible to marry military and environmental objectives in BIOT, but only at the exclusion of the Chagossians’ right of return”.9

Military construction and normal operations of the base, have generated numerous environmental concerns apart from creating a number of social issues. There has not been any extensive study on the environmental issues, due to denial of public access to the island. Diego Garcia’s lagoon has been subject to blasting and dredging. For instance, a paved airport runway was built on a 3.6km trail of land on crushed coral.  A number of trees were cut down to make way for the base, leading to wildlife retreat and soil erosion. Since its construction, the island has seen more than one million gallons of jet fuel leaks, water fouled with diesel fuel sludge, the warehousing of depleted uranium-tipped bunker buster bombs, and the likely storage of nuclear weapons.10 Anchor chains are also causing substantial damage to the corals especially in the northern basin of Diego Garcia.  US ships have been pouring waste including treated human sewage for three decades into the lagoon where a Foreign Commonwealth Officer has admitted that the British “no-discharge policy” were not being followed by US vessels. Various tests have found high levels (four times) of nutrients – nitrogen and phosphates causing damage to corals on

Diego Garcia.11 This questions the efficacy of the Marine reserve with the exclusion of Diego Garcia, where military continues with its environment damaging practices. Large amount of floating plastic debris has been found on the beaches of Chagos.


Potential Way Forward 

With the Indian Ocean becoming the centre stage of global geopolitics, it may be necessary to recognise the significance and utility of the archipelago to the US. However, the Outer Chagos Islands, which lie 100 miles from Diego Garcia and have never been used for defence purposes, could be ceded to Mauritius without jeopardizing the functionality of the base.12 In addition, adequate compensation may be provided to the indigenous population, for the damages suffered as a result of their displacement.

Co-management of the archipelagos could initiate bilateral talks between the UK and Mauritius. Ultimately, proper attention should be directed towards the military’s environmentally destructive activities rather than just creating an MPA.

Appropriate steps must be taken to ensure that the ‘no-discharge’ policy is followed strictly. Proper environmental assessments should be undertaken before any significant activities such as dredging, which may affect the island’s ecology. This would help in reducing the possibility of ecological damage and costs. After proper assessment, the particular operation may be tailored to reduce environmental damage.13 Stricter environmental monitoring system must be in place, especially to oversee the proper disposal of toxic waste, etc.

The role of multilateral co-operative mechanisms in resolution of such problems cannot be overstated; for instance, the IORA which has ‘marine security and environment’ as one of its agenda, can play a critical role in preserving the fragile environment as well as bringing about redressal for the social issues. Mauritius is a member country of the IORA and UK and US are dialogue partners.



Amidst the growing demands of the Chagossians to return back, and Mauritius’s claims of sovereignty, the UK has continued to lease the island to US until 2036. The MPA for now serves to bypass the sovereignty of Mauritius over the islands and the strategic importance of Diego Garcia, rather than ecological or social concerns. A number of measures can be taken to reduce the adverse impacts of the military installation at Diego Garcia, which includes renewed thrust, especially on the part of IORA.



About the Author:

Anjelina Patrick is a Research Associate at the National Maritime Foundation (NMF). The views expressed here are her own and do not reflect the official policy or position of the NMF. She can be reached at




  1. House of Commons Report, ‘Foreign Affairs Committee – First Report. The use of Diego Garcia by the United States’, 17 June 2014, Accessed on 21 November 2016,
  2. Peter Foster, ‘Diego Garcia: The facts, the history, and the mystery’, The Telegraph, 16 November 2016, Accessed on 22 November 2016,
  3. Thomas Fawns, “Diego Garcia: Exile, Rendition & Conspiracy”, Dictators, Dictatorships and Failed States, 27 February 2015, Accessed on 29 November 2016,
  4. Ewan W. Anderson, ‘Global Geopolitical Flashpoints: An Atlas of Conflict’, Routledge, 2014, pp.80-82
  5. Global Security, ‘Diego Garcia “Camp Justice” 7º20’S 72º25’E’, Global, Accessed on 30 November 2016,
  6. UN General Assembly, Declaration on the Granting of Independence to Colonial Countries and Peoples, 14 December 1960, A/RES/1514(XV), Accessed 1 December 2016,
  7. R. C. Sheppard, “Reefs and islands of the Chagos Archipelago, Indian Ocean: why it is the world’s largest no-take marine protected area.” NIH Public Access : Author Manuscript. United Kingdom: National Institute of Health,UK, March 2012.
  8. Anthony E Cassimatis, “The Chagos UNCLOS Arbitration: Maritime, Fishing and Human Rights Issues and General International Law”, TC Beirne School of Law,
  9. Harris, Peter. “A Political Trilemma? International Security, Environmental Protection and Human Rights in the British Indian Ocean Territory.” International Politics, 2013: 6-9.
  10. David Vine, “Environmental Protection of Bases?” Foreign Policy In Focus, April 22, 2010.
  11. Cahal Milmo, “Exclusive: British Government under fire for pollution of pristine lagoon”, Independent, 28 March 2014.
  12. Harris, Peter. “A Political Trilemma? International Security, Environmental Protection and Human Rights in the British Indian Ocean Territory.” International Politics, 2013: 6-9.
  13. Sheppard, C. R. C.; S. Smith; J. R. Turner & D. Marx (2008) Corals and sediments in the lagoon in Diego Garcia and effects of ship anchoring: Report to the Foreign and Commonwealth Office British Indian Ocean Administration and US Navy, 23pp, BIOT Administration, London
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