The Chagos and Maldives chain of islands was created after India slid north, millions of years ago, crumpling up the Himalayas in front of it. Upwelling lava from a hotspot deep in the earth’s mantle created the bases of these islands; those of Chagos were pushed up 45 million years ago. The islands’ lava cores then began their long, slow subsidence, while reefs from the remains of living coral built up around them. Amazingly, the coral under Diego Garcia is about a mile deep.

The French assumed sovereignty in the late 18th century and began to exploit the islands for copra, originally employing slave labour. However the islands were never commercially important.

During the Napoleonic wars Britain captured Mauritius and Reunion from France. Under the Treaty of Paris in 1814, Britain restored Reunion to France and France ceded Mauritius to Britain together with its dependencies which comprised Seychelles and other islands, including the Chagos.1 In the late 19th century Charles Darwin drew extensively on scientific surveys of the Chagos archipelago for his theories on coral reefs.

In 1965 the Chagos Islands were detached to become part of the British Indian Ocean Territory, with the full agreement of the Mauritius Council of Ministers and a grant paid to Mauritius, The Territory is administered by the UK Government through the BIOT Administration. There are no economic activities on the islands. UK/US Agreements regulate the use of the Territory for defence purposes.

The following are features which make the Chagos an outstandingly important environmental site and threats which make comprehensive conservation so important.

The Chagos contain some of the world’s healthiest coral reefs and the world’s largest surviving coral atoll. Scientists fear that half of the world’s coral reefs could be lost by 2025. It is essential to save them: hundreds of millions of people in the world depend on healthy reefs in one way or another. Living reefs provide food, protect beaches from erosion and form a treasure house of genetically diverse creatures and plants.

The wildlife biodiversity of Chagos is very rich. It provides at least 220 coral species and over 1000 species of fish in a surviving stronghold.

It is also a refuge and breeding ground for large and important populations of sharks, dolphins, marine turtles, rare crabs, birds and other vulnerable marine and island species. In marine terms BIOT is by far the most bio-diverse part of the UK and its Overseas Territories.

The archipelago is isolated and at the very centre of the Indian Ocean where it acts as an ‘oasis’ for marine and island species (which are nearly all in decline elsewhere under pressure from the effects of massive recent human population growth in the region).

Most of the Chagos is uninhabited. This is the main reason why the ecology of the Chagos is full of diverse life, a rare surviving example of nearly pristine tropical habitats.