Changes to the natural history of islands in the Chagos Atolls, Central Indian Ocean, during human settlement (1780-1969), and prospects for restoration

Abstract

The Chagos Archipelago (British Indian Ocean Territory, or BIOT) has 55 islands totalling approximately 5,000 ha spread over approximately 50,000 km 2 of the central Indian Ocean. From the first human settlements, which occurred in the late 1700s, and for the following century, all of the larger islands were converted into coconut plantations. During this period the disturbance to and elimination of the native flora and fauna in Chagos atolls was especially profound because these islands were used solely for the production of coconut and its products. Regarding vegetation, many times more species were introduced than were native, and several introduced species subsequently became invasive. The bird colonies, turtles and the land crabs were hugely reduced due to human consumption, land disturbance and the introduction of rats and other inappropriate and often free-ranging animals, such as pigs. The condition of the reefs, however, remains excellent, such that the area was declared a no-take marine reserve in 2010. For some years, BIOT was the world’s largest marine no-take conservation area. This status was achieved mainly because of its reefs; the islands are still heavily dominated by increasingly derelict, rat-infested coconut plantations and lack birds on most previously planted islands. However, on the smallest islands, many no larger than a few ha in size, there are both native plant communities and huge numbers of breeding seabirds. These relatively undisturbed fragments are acting as the core of current conservation efforts to restore some of the larger islands to their pre-plantation condition. This paper documents, as far as is possible from the relatively sparse archival documents, the course of events and extent of the terrestrial changes that took place in this archipelago before modern concepts of conservation emerged and remarks on the present, planned and funded restoration efforts that can be based on such knowledge.