Monster starfish attack Great Barrier Reef
The Great Barrier Reef is under attack from a species of starfish measuring more than 1 metre across that spends half its life eating coral, scientists say.
Australia's top tourist attraction has lost half its coral in the last 27 years and the crown of thorns starfish is responsible for around 42 per cent of that shrinkage, researchers at the Australian Institute of Marine Science in the far-north Queensland city of Townsville said.
Only storm damage from tropical cyclones (48 per cent) had a greater impact, with bleaching responsible for the remaining 10 per cent.
"There is a strong case for direct action to reduce (starfish) populations and further loss of corals," the authors wrote in a paper published in the journal Proceedings of the National Academy of Sciences.
They said coral cover could increase by nearly 1 per cent a year without the damage done by the Ancanthaster planci. Each female of the species can lay 60 million eggs in a single breeding season.
The Great Barrier Reef, the world's best-protected coral reef, is an assembly of 2,900 individual reefs stretching 2,600 kilometres down the east coast. It draws 2 million visitors a year and underpins tens of thousands of jobs in tourism.
The team undertook 2,258 surveys on 214 areas over 27 years. It speculated that the decline may have begun long before the research project began in 1985.
The scientists said that improving water quality by reducing the run-off of fertiliser and pesticides from farms on the east coast could slow the march of the coral-munching starfish.
They warned that coral cover was predicted to fall to 5-10 per cent within the next 10 years in the absence of progress to mitigate storm damage, reduce bleaching and cut starfish numbers.