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Assessing coral resilience and bleaching impacts in the Indonesian archipelago

Maynard J.; Wilson J.; Campbell S.; Mangubhai S.; Setiasih N.; Sartin J.; Ardiwijaya R.; Obura D.; Marshall P; Salm, R.; Heron S.; Goldberg J.
2/14/2012
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Indonesia has more reef resources than any other country but its’ reefs are also the world’s most threatened due to the large population’s high dependence on marine resources. Managers and conservationists face the challenge of preserving the world-renowned biodiversity of Indonesia’s reefs while facilitating sustainable use. Threats posed by human activities are compounded by the threat of climate change, which is predicted will bring more frequent and severe bleaching events, like those observed in Indonesia in 1998/1999. Climate change greatly increases the impetus to manage reefs to support and maintain their resilience i.e. their natural capacity to resist and recover from disturbances.

In 2009, reef resilience assessments were undertaken at over 120 sites throughout the Indonesian archipelago including Aceh, Java, Bali and West Papua. In 2010, elevated water temperatures associated with an El Niño / La Niña event caused bleaching in Aceh and Bali and also at Southeast Sulawesi. Follow up surveys showed the severity and impact of bleaching varied among study regions and among sites within study areas.  This provided an opportunity to assess if resilience scores reflected bleaching severity and impact at a large number of sites.  Through this process which involved a workshop of field practicioners and experts, we also critically evaluated how resilience assessments are conducted, developed a framework for presentation and communication of resilience scores to inform management and identified next steps for refining resilience assessments. 

Variation in bleaching among sites within study areas was better explained by the proportion of the community made up of bleaching susceptible taxa than resilience scores.  Variation in bleaching severity and mortality among study areas was related partly to temperature stress during the bleaching event but also strongly influenced by past variability in summer temperatures.  Areas with high variability in summer temperatures had significantly less severe bleaching and less mortality than areas with low variability in summer temperatures.  Including these factors (community composition, thermal stress and thermal history) in future resilience assessments will strengthen their capacity to accurately identify sites which are likely to be resistant to future bleaching events. 

This report outlines the largest-ever undertaking of a coral reef resilience assessment and the only to be paired with detailed surveys of the impacts of a severe bleaching event. As a whole, the project is a case study that can serve as an example to others as to how to use reef resilience assessments to inform management decisions.

Suggested citation: Maynard J, Wilson J, Campbell S, Mangubhai S, Setiasih N, Sartin J, Ardiwijaya R, Obura D, Marshall P, Salm R, Heron S, and Goldberg J. 2012. Assessing coral resilience and bleaching impacts in the Indonesian archipelago. Technical Report to The Nature Conservancy with contributions from Wildlife Conservation Society and Reef Check Indonesia. 62 pp.

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