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Deforestation is killing Madagascar’s coral reefs

Antongil Bay

Sediment carried by rivers draining deforested areas in Madagascar is smothering local coral reefs, increasing the incidence of disease and suppressing growth, report new studies published in the journals Biogeosciences and Marine Pollution Bulletin.

The first study looked specifically at coral communities in Antongil Bay, located in northeastern Madagascar, while the second included data from Western Madagascar. Antongil Bay is Madagascar’s largest bay and world-famous as nursing grounds for humpback whales.

The authors analyzed coral’s luminescent bands, which reveal the growth history of coral much like growth rings of a tree. They found that corals near rivers “showed clear signs of disease and distorted growth patterns”, according to study co-author Jens Zinke of the University of Western Australia’s Oceans Institute.

“Results from the study suggest that changes in land use – primarily the removal of forests – and Madagascar’s increased population density are the key drivers of long-term reef sedimentation trends,” Zinke added in a statement. “This is the first direct evidence that catchment activity in Madagascar through deforestation and land use practices affects near-shore reef ecosystems.”

Madagascar has suffered from widespread deforestation. Around Antongil Bay forests have been cleared for rice cultivation and cattle grazing. Remaining forests have been heavily impacted by illegal rosewood and ebony logging.

Zinke says the results underline the importance of holistic approaches to conservation.

“Just as importantly, these results reinforce the need to incorporate terrestrial land-use management in the design of coral reef protection networks in the region,” he said. “There is a dire need to combine efforts on terrestrial and marine conservation in unison to sustain Madagascar’s biodiversity.”

C.A. Grove at al (2012). Spatial linkages between coral proxies of terrestrial runoff across a large embayment in Madagascar, Biogeosciences, 9, 3063-3081, doi:10.5194/bg-9-3063-2012.

Joseph Maina et al (2012). Linking coral river runoff proxies with climate variability, hydrology and land-use in Madagascar catchments. Marine Pollution Bulletin, Available online 31 July 2012

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