Regional Impacts - British Indian Ocean Territory


Corals killed by sea warming in BIOT © Charles SheppardThe British Indian Ocean Territory has one of the largest and most isolated coral reef and island systems. Because it is largely uninhabited, it is one of the few remaining tropical areas that could be used as a reference location for observing the impacts of climate change without the presence of human-induced environmental stresses, such as pollution and land-use in the coastal zone.


Observed change

  • Rising sea temperatures have contributed to the death of coral reefs. There have been several coral bleaching episodes following the major bleaching event in 1998, which destroyed some 80 per cent of live coral cover to a depth of 30m after sea surface temperatures rose to almost 30°C in the Chagos Archipelago.  Bleaching events have taken place as recently as 2004. 
  • Some of the islands are experiencing coastal erosion caused by sea level rise and possibly the loss of sand production following the mass mortality of coral reefs. Some areas have been more badly affected than othersSame coral species in good health © Charles Sheppard.
  • Sea level rise in Diego Garcia has averaged 0.54 cm per year since 1986, but appears to be accelerating (Sheppard and Spalding, 2003).


Implications and possible future impacts

  • Loss of reefs is leading to loss of some fish and other marine species. The biodiversity of reefs and their biological integrity is being compromised. 
  • Erosion is already causing and will continue to cause damage to the shoreline and to buildings and structures along the coast.
  • As the sea level rises, the reef flats (the shallow, flattest part of the reef that is often uncovered at low tide) at the mean low tide level will become less effective in offering the shoreline protection from waves.