The Chagos Marine Protected Area is the largest no-take marine reserve in the world, covering a total surface area of 640,000 square kilometres (397,667 sq mi) – over twice the surface area of the UK. No-take marine reserves are areas of the sea in which there is no fishing allowed and as little other human disturbance as can be reasonably arranged. The Chagos reserve was established by the British government on 1 April 2010, and its protection is funded through 2015 with financial support from the Bertarelli Foundation.
The Chagos marine reserve protects the world’s largest coral atoll (the Great Chagos Bank) and has one of the healthiest reef systems in the cleanest waters of the world, supporting nearly half the area of good quality reefs in the Indian Ocean.
Chagos, an archipelago of 55 tiny islands, is located in the central Indian Ocean, about 1,500 km from the southern tip of India, 3,400 km due east of Africa and 3,000 km west of Indonesia. Politically, Chagos is constituted as the British Indian Ocean Territory (BIOT).
Previous to the establishment of the marine reserve, the Chagos Archipelago had been declared an Environmental (Preservation and Protection) Zone with legislation in place to protect much of the area’s natural resources. Commercial fishing, however, was licensed for both reef fish and tuna. Though the UK government has opposed the area being proposed as a World Heritage Site, it has agreed to treat it as such in order to preserve its environmental value.
The case for a large scale marine reserve in the Chagos was first put forward by a consortium of conservation organisations led by the Chagos Environment Network, a collaboration of nine leading scientific and conservation organisations, in “The Chagos Archipelago: Its Nature and the Future” which was launched in March 2009. The Chagos Environment Network was the leading advocate for the reserve during the consultation period and organised two of the major petitions in favour of the reserve being set up.
From the 10th November 2009 to the 5th 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. Respondents were asked not only whether they believed that the MPA should be established but also to what degree they thought it should be protected, either to establish a fully no-take marine reserve or a less protected marine protected area that would allow some fishing.
The response to this consultation was high, with over 250,000 people expressing their views on the issue either through the use of petitions or more lengthy written replies. Over 90% declared their support for greater marine protection, with the majority believing that it should be a no-take marine. Following this response, the total area of the Chagos’ Exclusive Economic Zone was declared a fully no-take area, with the exception of a 3-mile zone around the island of Diego Garcia.
Ninety percent of the United Kingdom’s biodiversity lies in its Overseas Territories, and the Chagos archipelago is by far the most biodiverse marine area in the United Kingdom’s waters. Its habitats include extensive shallow limestone reefs and associated 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 unique 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. The area hosts 220 species of coral including the Ctenella chagius, a variety of brain coral believed to be endemic to the atoll, and staghorn coral which is important to protecting low-lying islands from wave erosion.
The fish of the region are equally diverse, with at least 784 different species having been identified including the Chagos clownfish (Amphiprion chagosensis) which is endemic to the archipelago. The marine reserve is an important refuge for overfished pelagic species such as manta rays, sharks and tuna. It is also believed, based on results of research on similar deep water and diverse underwater terrain in other parts of the world, that the deep water trench is very likely to harbour a variety of previously undiscovered species.
The islands of the archipelago provide vital nesting sites for green and Hawksbill turtles (Chelonia mydas and Eretmochelys imbricata). Since the hawksbill turtle is labelled ‘critically endangered’ and the green turtle ‘endangered’ on the IUCN Red List, the Chagos populations are considered to be of international importance. It is estimated that 300-700 hawksbill and 400-800 green turtles nest annually across the 55 islands of the archipelago.
The breeding seabirds of the Chagos are considered to be of international importance. 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, though the presence of human-introduced rats on several of the other islands severely hinder seabird nesting on these.
Five species are considered to be breeding 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 world’s largest terrestrial arthropod, the coconut crab (Birgus latro) can reach over one metre in leg span and a weight of up to five kilograms. Since its shells are in extremely high demand as tourist souvenirs and it is over-collected for food, the coconut crab is usually rare in the areas where it is found. It is extremely abundant on the islands of the Chagos archipelago, with an overall density in the conservation area on Diego Garcia of 298 crabs per hectare – the highest ever recorded. 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.
Enforcement of the marine reserve is carried out through active patrolling by the M/V Pacific Marlin. The patrol vessel, which has a maximum speed of 12.5 knots, makes an average of one extended trip (106 days) around the archipelago every four months. In 2011, twelve vessels were arrested and prosecuted for illegal fishing in the reserve.