The Chagos Marine Protected Area, located in the central Indian Ocean within the British Indian Ocean Territory of the United Kingdom, is one of the largest officially designated marine protected areas in the world. It is also one of the largest protected areas of any kind on Earth, whether on land or in the ocean. The area was created by the British government on April 1, 2010, as a large, connected marine reserve. It covers 640,000 square kilometers (250,000 square miles) of ocean water, including about 70 small islands and seven atolls in the Chagos Archipelago.
The creation of the protected area was controversial because the Chagossian people were forced to leave the archipelago, including the outer islands, to allow the United States to build a military base on Diego Garcia. This forced removal has been called ethnic cleansing. A leaked message from the U.S. State Department suggested that creating the reserve to limit fishing would help prevent the Chagos Islands’ former residents or their descendants from returning. The message also stated that the protected area would allow environmental damage caused by military activities, as the British government wanted to ensure no restrictions on military operations in the area. A rule in the protected area allows people working at the U.S. base on Diego Garcia to continue fishing. In 2010, more than 28 tons of fish were caught for use by the base’s personnel.
On March 18, 2015, the Permanent Court of Arbitration ruled unanimously that the marine protected area was illegal under the United Nations Convention on the Law of the Sea. The court stated that Mauritius had the right to fish in the waters around the Chagos Archipelago, the right to eventually reclaim the islands, and the right to preserve any minerals or oil found in or near the islands before their return. This decision is final and legally binding. The protected area is now being discussed between the United Kingdom and Mauritius.
The Chagos Marine Protected Area is managed with help from the Chagos Trust, which receives funding from donations and the British government. Visitors are generally not allowed, though private yachts traveling through the Indian Ocean may apply for permits to moor outside the strict nature reserve areas, starting in 2016.
Description
The Chagos marine reserve helps protect the world's largest coral atoll, called the Great Chagos Bank. This area has one of the healthiest reef systems in the world's clearest waters and supports nearly half of the good-quality reefs in the Indian Ocean. No-take marine reserves are ocean areas where fishing is not allowed, and other human activities are kept to a minimum to protect the environment.
The Chagos Archipelago includes 70 small islands and atolls located in the central Indian Ocean. It is about 1,500 kilometers from the southern tip of India, 3,400 kilometers east of Africa, and 3,000 kilometers west of Indonesia. Politically, Chagos is classified as the British Indian Ocean Territory (BIOT).
Establishment
Before the marine reserve was created, the Chagos Archipelago was designated an Environmental Protection Zone with laws to safeguard its natural resources. Commercial fishing for reef fish and tuna was allowed under licensed agreements. Although the UK government has resisted efforts to classify the area as a World Heritage Site, it has agreed to treat it as one to protect its environmental value.
The idea of creating a large marine reserve in the Chagos was first proposed by a group of conservation organizations, led by the Chagos Environment Network. This group included nine major scientific and conservation organizations and published a report titled "The Chagos Archipelago: Its Nature and the Future" in March 2009. The Chagos Environment Network was the main supporter of the reserve during public discussions and organized two major petitions in favor of the reserve.
Between November 10, 2009, and March 5, 2010, the UK government conducted a public consultation to gather opinions on whether a marine protected area (MPA) should be established in the archipelago. People were asked not only if they supported the MPA but also how much protection they believed it should have, such as a fully no-take marine reserve or a less strict protected area that would allow some fishing.
The consultation received a strong response, with more than 250,000 people sharing their views through petitions or written responses. Over 90% supported stronger marine protection, with most believing it should be a no-take marine reserve. Concerns about losing about £800,000 annually from tuna fishing licenses were frequently mentioned as a potential challenge. In the final months before the reserve was established, the Bertarelli Foundation offered to cover the financial gap left by the loss of fishing income and to fund an enforcement boat for five years. As a result, the entire Chagos Exclusive Economic Zone was declared a fully no-take area, except for a 3-mile zone around Diego Garcia Island.
On April 1, 2010, the British Foreign Secretary directed the BIOT Commissioner to establish the Marine Protected Area, which was the last possible date before the UK Parliament dissolved for the 2010 general election. The creation and first five years of the Chagos MPA have been supported by major funding from the Bertarelli Foundation.
Ecology and biodiversity
Ninety percent of the United Kingdom's biodiversity is found in its Overseas Territories, and the Chagos archipelago is the most biodiverse marine area in the UK's waters. Its habitats include large shallow limestone reefs and related environments, about 300 seamounts, and a deep sea trench—an underwater canyon more than 4,900 m (16,000 ft) deep.
One of the most unusual features of the Chagos marine environment is its very healthy and diverse coral cover, which remains dense even in deep water and on the steep outer slopes of reefs. The area is home to 220 coral species, including Ctenella chagius, a type of brain coral found only in the Chagos, and staghorn coral, which helps protect low-lying islands from wave erosion. Chagos serves as an important benchmark for coral conservation and acts as a 'natural laboratory' for studying complex ecosystems.
The fish in the region are also very diverse, with at least 784 species identified, including the Chagos clownfish (Amphiprion chagosensis), which is found only in the archipelago. The Chagos Marine Reserve, which has no fishing allowed, has helped fish populations recover within its boundaries. The reserve is a critical refuge for overfished pelagic species such as manta rays, sharks (including whale sharks), tuna, and is especially important for globally threatened species like the silky shark. Research suggests the deep trench may also be home to many previously unknown species.
The islands of the archipelago provide important nesting sites for green and hawksbill turtles (Chelonia mydas and Eretmochelys imbricata). The hawksbill turtle is listed as 'critically endangered' and the green turtle as 'endangered' on the IUCN Red List, making the Chagos populations vital for global conservation. It is estimated that 300–700 hawksbill and 400–800 green turtles nest each year across the 55 islands of the archipelago.
The Chagos Archipelago supports a variety of cetacean species, such as three populations of blue whales and toothed whales (including sperm whales, pilot whales, orcas, pseudo-orcas, Risso's dolphins, and spinner dolphins). Dugongs, which are now extinct in the region, were once common there, leading to the name "Sea Cow Island."
The breeding seabirds of the Chagos are also of international importance. The archipelago is home to 18 different seabird species, and 10 of its islands are designated as Important Bird Areas (IBAs) by BirdLife International. This makes the region the most diverse breeding seabird community in the tropical area. However, the presence of human-introduced rats on some islands hinders seabird nesting.
Five seabird species breed in internationally significant numbers: the sooty tern (Sterna fuscata), the brown and lesser noddy (Anous stolidus and Anous tenuirostris), the red-footed booby (Sula sula), and the wedge-tailed shearwater (Puffinus pacificus).
The coconut crab (Birgus latro), the world's largest terrestrial arthropod, is abundant on the islands of the Chagos archipelago. On Diego Garcia, the conservation area has a density of 298 crabs per hectare—the highest recorded globally. Because coconut crab larvae can travel long distances, the Chagos population is important for replenishing numbers in other parts of the Indian Ocean.
Scientific research
Scientists and conservationists are working to learn more about these islands, remove non-native plant and animal species, and help native plants grow again. These efforts are important for protecting the Chagos islands and the world's variety of living things. In February and March 2013, a research trip was conducted in the Chagos Marine Protected Area (MPA). This trip, supported by the Bertarelli Foundation and worked with Stanford University and the University of Western Australia, tested electronic tagging to see if remote tools could track the movement of important ocean species in the area. Five types of electronic tags were used in this study, with a total of 99 tags placed on 95 animals. An array of acoustic receivers was also set up around two northern atolls to detect animal movements.
Pollution
A report by a scientific adviser to the UK's Foreign and Commonwealth Office, which the British government did not share, states that the Pacific Marlin, an old tugboat used by London to patrol the British Indian Ocean Territories, released waste while docked near US Navy ships. The Independent newspaper also reported that US ships have dumped waste, including treated human sewage, into the lagoon on Diego Garcia for 30 years. Diego Garcia has served as an important military base for the United States since the 1970s.
Opposition to declaration of a Marine Protected Area
The MPA has been criticized by Mauritius, which previously managed the Chagos Islands before they were separated by the UK when the colony became independent. Both Mauritius and the Chagos Islands were once British territory, but they did not share the same nationality. In December 2010, the Government of Mauritius started legal action against the UK under the United Nations Convention on the Law of the Sea (UNCLOS) to question the legality of the marine protected area. Mauritius argues that the UK, which is not a "coastal State" under international law, had no right to create the MPA around the Chagos Archipelago. Mauritius also claims the MPA conflicts with the rights of the Chagossians.
The original Chagossians were removed from Diego Garcia, the largest island, 40 years earlier to make space for the US Naval Support Facility Diego Garcia, which includes port facilities and an airstrip capable of handling large aircraft. The Chagossians say the MPA would prevent them from returning because it would stop them from fishing, their main source of income. Roch Evenor, secretary of the UK Chagos Support Association, stated, "There would be a natural injustice. The fish would have more rights than us. Conservation groups have been tricked into supporting the government’s plan to stop us from returning."
In a letter to Greenpeace, the Mauritian Lalit de Klas political party wrote, "The British government’s plan for a marine protected area is a clear and dishonest attempt to keep the people of Mauritius and Chagos from returning to part of their own country."
In 2012, the Greenpeace ship SY Rainbow Warrior was in the Indian Ocean region, but the government of Mauritius initially prevented it from stopping at Port-Louis harbor. This was because Greenpeace had supported the UK’s controversial marine park project in the Chagos Archipelago. Mauritius called Greenpeace’s actions "hypocritical" and expressed regret that Greenpeace ignored the UK’s illegal separation of the Chagos Archipelago from Mauritius, even though international groups recognize the islands as part of Mauritius. Mauritius stated that Greenpeace, which claims to protect the environment, showed inconsistency by not speaking out about the proposed marine park.
In official communication, Greenpeace International stated:
On December 1, 2010, WikiLeaks released a leaked US Embassy London diplomatic message from 2009, revealing British and US plans to create the marine nature reserve. The message describes a conversation between US Political Counselor Richard Mills and British Foreign and Commonwealth Office Director Colin Roberts, in which Roberts said, "Establishing a marine park would effectively end resettlement claims by the islands’ former residents." Richard Mills concluded:
The message, which mentions that the marine reserve was proposed by the Pew Charitable Trust, was classified as confidential and restricted to "no foreigners." It was leaked as part of the Cablegate collection.
The same message explained that the protection would allow environmental damage if caused by military use: "The terms of reference for the marine park would clearly state that the BIOT, including Diego Garcia, was reserved for military purposes. … The marine reserve could be a 'win-win situation' for monitoring the BIOT. … The government wanted 'no constraints on military operations' due to the marine park." An exemption in the MPA allows fishing to supply food to the US military base; in 2010, more than 75 kilograms (165 pounds) of fish were caught daily for the 3,200 personnel stationed there.
Chagos Marine Protected Area declared illegal
After the Permanent Court of Arbitration made its decision, the Prime Minister of Mauritius stated that this was the first time an international court or tribunal had examined and criticized the United Kingdom's actions regarding the Chagos Archipelago. He described the ruling as a key step in the long effort by Mauritius's governments over many years to fully exercise their authority over the Chagos Archipelago in political, diplomatic, and other areas. The tribunal carefully reviewed the promises made by the United Kingdom to Mauritian leaders during the Lancaster House talks in September 1965. The UK claimed these promises were not legally required and had no place in international law. However, the tribunal strongly disagreed, stating that these promises became a legal agreement that the UK must follow once Mauritius gained independence. The tribunal also concluded that the UK's commitments to Mauritius about fishing rights and rights to oil and minerals in the Chagos Archipelago are legally required.
Exclusion of Chagossian peoples
The Chagos Marine Protected Area (MPA) was established in 2010 during a legal discussion about whether people from Chagos could return to the island after being forced to leave 40 years earlier. If they return, they would not be allowed to fish for food because the MPA is a strict no-take reserve where fishing is completely banned. However, fishing is permitted around Diego Garcia, the island where a joint UK-US military base is located. Diego Garcia is the only current source of pollution in the archipelago and is exempt to support military operations. Although there are disputes over who owns the archipelago, the UK holds legal control over Chagos and manages access to and use of resources on the islands. A plan for Chagossian resettlement, reviewed by international experts, will be discussed in June 2025. In June 2025, the Great British PAC, along with Chagossian activists, will take legal action to challenge the UK government’s decision to sign a restitution agreement.