Half the Barrier Reef has disappeared: report

A sobering study released today shows more than half of Australia's Great Barrier Reef has disappeared over the past 27 years.

Scientists from the Australian Institute of Marine Science in Townsville have found the loss of coral is caused mainly by cyclones and crown-of-thorns starfish.

Coral bleaching is also to blame.

The study, published in the Proceedings of the National Academy of Sciences, warns the rate of the reef's decline has been higher than previously thought.

It says if current trends continue, its coral cover could halve again by 2022 and it may lose the biodiversity for which it was listed as a World Heritage Area.

The study argues that stopping the progress of the crown-of-thorns starfish is crucial to the recovery of the 3,000km-long reef.

But scientist John Gunn says the future of the ecosystem could be under threat if the loss of coral is not stopped.

"Accumulative impacts of storms and crown-of-thorns and two bleaching events have had a quite devastating effect over the last three decades," he said.

"We're very concerned that this is a bit of a crossroads for the reef and this data is very authoritative.

"I can't pretend that if we had this type of impact continuing and we had some of the possible impacts of climate change in the future that the Great Barrier Reef really is at threat."

Cumulative impacts
Mr Gunn, chief executive of the institute in Townsville, says damage to the reef is patchy, with some areas affected more than others.

"There are parts of the reef that are still pretty much as we'd like the whole of the reef to be, and they give us some hope that that's what we could achieve with the whole of it.

"These are areas north of Cooktown and they're pretty healthy reefs, in fact they're beautiful.

"It's the areas that really have these cumulative impacts, the three factors that we take account of in the study that have really come under sort of major pressure.

"But even there, there are reefs that are still very, very lovely to visit."

Last week AM reported a Climate Commission study that found global warming was putting increasing pressure on the Great Barrier Reef, potentially causing more bleaching events.

AIMS research director Dr Jamie Oliver says stopping the crown-of-thorns starfish could be the key to the reef's long-term survival.

"Now this is a native species which outbreaks in enormous proportions, killing off large proportions of the reef, and this is something that we may be able to take some action on," he said.

"If we can at least disrupt these outbreaks, that may give the reef a chance to recover from the other factors that we describe such as cyclones and coral bleaching."

More at the link, as well as video interview with John Gunn.