Great Barrier Reef
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Half of Great Barrier Reef 'disappeared' in past 27 years

2 October 2012 Last updated at 07:07 BST

More than half of Australia's Great Barrier Reef has disappeared in the past 27 years, according to a new study by scientists.

Various factors, including cyclones, coral bleaching and the Crown of Thorns starfish, have been blamed.

The BBC's Duncan Kennedy reports from Sydney.