Ecological and Socio-Economic Impacts of Mass Coral Bleaching

The unprecedented impacts of the 1997-98 mass coral bleaching event, resulting in up to 80-percent mortality in some of the reefs affected, has catalyzed new scientific and policy initiatives aimed at understanding and responding to this issue.

Coral bleaching occurs when zooxanthellae — the symbiotic algae that provide coral polyps with nutrients and their color — are lost from coral tissues. Severe or extended bleaching events ultimately result in coral mortality. At a local scale, many stressers cause coral bleaching, such as tropical storms, disease, sedimentation, destructive fishing, over-exploitation of reefs and salinity and temperature variations.

Mass coral bleaching is a large-scale, bleaching event that appears to be linked with temperature variations related to global climate change. Mass bleaching events are strongly correlated with increased sea surface temperatures of 1ºC or more above average. Observed and predicted global warming trends suggest that sea surface temperatures are increasingly reaching these heightened levels with the result that the occurrence and intensity of bleaching is expected to increase over the next 30 to 50 years. These mass bleaching events compound stress on reefs from local anthropogenic sources.

Because many island and coastal populations depend on coral reefs for nutrition, fisheries and tourist income, as well as coastal protection, mass coral bleaching may result in significant social and economic impacts, as well as potential loss of marine biodiversity. The need to better understand both the impacts from and potential responses to coral bleaching are therefore both important.

The Coral Bleaching Program began in October 1999 and ended in March 2001 as a partnership between CRC and the U.S. Agency for International Development (USAID) funded by the U.S. State Department. The overall goal of the program is to support the U.S. Coral Reef Task Force and the International Coral Reef Initiative efforts in the East Asia-Pacific (EAP) region to understand the science of coral bleaching, as well as the ecological and socio-economic impacts of coral bleaching and associated mortality. To meet this goal the Coral Bleaching Program works closely with partners in the EAP region and in tandem with US and global reef conservation initiatives to bring a rigorous and integrated response to this emerging issue. The focus of this effort is to:

  1. Financially and technically support the Convention on Biological Diversity (CBD) Expert Consultation on coral bleaching;
  2. Convene a special session on coral bleaching at the 9th International Coral Reef Symposium; and
  3. Plan and coordinate ecological and socio-economic studies of coral bleaching impacts.