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Status of coral reefs in the Indian Ocean

Status of coral reefs classified by potential threat from human activities

Over half of the region’s reefs are at risk. Almost all of the reefs off India and Sri Lanka are under high potential threat. Destructive fishing practices, overexploitation, pollution, sedimentation from land clearings, and coral mining for lime have all been blamed for the widespread degradation of Sri Lankan reefs.[1][2] Off East Africa, most documented damage to coastal habitats occurs near major towns and cities, due to sewage discharge and overexploitation. Blast fishing and agricultural runoff also pose significant threats. Our results indicate that the great majority of reefs of the Chagos Archipelago and Maldive Islands are under low potential threat (according to this study, close to 90 percent of reefs in the Maldives are at low risk). All told, the Indian Ocean accounts for roughly 15 percent of the world’s mapped reefs.

During review of these final threat classifications, coral reef experts provided the following observation: The reefs in the northeastern Seychelles around Mahé and Curieuse Islands were estimated to be under medium and high threat. This is a potential overestimation of threat.
Mombasa Marine Park

Estimated threat to coral reefs: low medium high

Case studies:

Data Sources: Reef locations are based on 4-kilometer-resolution gridded data reflecting shallow coral reefs of the world by the World Conservation Monitoring Centre (WCMC).

Reefs are classified according to the Reefs at Risk Indicator, an estimate of potential threat to coral reefs developed at the World Resources Institute (WRI). This estimate is a composite of four separate risk factors:

  • Coastal development
  • Marine-based pollution
  • Overexploitation, and
  • Inland pollution and erosion

Notes

1. Rajasuriya, De Silva, and Ohman, “Coral Reefs of Sri Lanka: Human Disturbance and Management Issues,” Ambio 24, nos. 7-8 (December 1995), 428-29.

2. Arjan Rajasuriya, “Present Status of Coral Reefs in Sri Lanka,” in Proceedings of the Colloquium on Global Aspects of Coral Reefs: Health, Hazards and History (University of Miami, 1993), 411.