A team of international scientists, including a researcher from The University of Western Australia, has found that soil erosion, land degradation and climate change pose a mounting threat to coastal reefs and their ecosystems in the western Indian Ocean.The study examined sediment and freshwater discharge over recent decades in two catchments in Madagascar’s Antongil Bay and the island nation’s Great Barrier Reef of Tulear, and the climatic processes that drive them.

The unique study incorporated hydrological catchment modeling as well as coral data over the past 60 years.

This was possible because Madagascar’s giant Porites corals have grown continuously over several centuries at 1-2cm annually and record the changes in their environment by absorbing trace elements into their skeleton.

Deforestation is often linked with degradation of terrestrial ecosystems but until now no study has revealed its impact on adjacent coral reefs.

“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 but that these are slow processes,” said study co-leader Dr Jens Zinke, of UWA’s Oceans Institute.

Dr Zinke said those factors combined with climate changes – including hinterland rainfall, temperature and El Niño-Southern Oscillation – to influence the amount of sediment transported through river run-off, which is subsequently deposited in coastal waters and reflected in elevated geochemical indicators in corals.

Read the full article from: http://www.news.uwa.edu.au/201208034880/research/ancient-coral-reefs-risk-deforestation-and-land-use-practices