SYDNEY: The world heritage-listed Great Barrier Reef has lost half of its coral in the past 27 years according to the world’s most comprehensive and longest study of a coral reef ecosystem.
The study of 214 reefs by researchers at the Australian Institute of Marine Science (AIMS) in Townsville, was published yesterday in the journal Proceedings of the National Academy of Science.
“If the trend continued, coral cover could halve again by 2022,” said AIMS scientist Peter Doherty, one of the originators of the long-term monitoring project.
Here come the starfish
The researchers gathered data by snorkelling while being towed by boat around the edges of the reef. They collected data from over 2,000 reef surveys along the Great Barrier Reef since the studies commencement in 1985.
The results identified that the three main causes of damage to the reef were: storm and cyclone damage as evidenced by shattered coral, 48%; predation by the crown-of-thorns starfish as evidenced by their presence or the algae-covered coral skeletons they leave behind (Acanthaster planci) 42%; and coral bleaching 10%.
The good news is that reefs along the less developed coast north of Cooktown, where starfish predation is less of a problem, showed no overall decline. “We can’t stop the storms, but perhaps we can stop the starfish. If we can, then the reef will have more opportunity to adapt to the challenges of rising sea temperatures and ocean acidification,” said John Gunn, CEO of AIMS.
Corals could recover if starfish stopped
The voracious crown-of-thorns starfish are natives of the reef but since the 1960s, their numbers have exploded in a series of outbreaks that have been linked to floods. Fertilizer run-off triggers algal blooms, food for the starfish spawn whose numbers explode.
According to Doherty, some progress has been made halting fertilizer run off since 2005 with the implementation of the $375 million Reef Plan but he said that biocontrol of the starfish using its endemic pathogens also needs to be considered.
“If we could stop starfish tomorrow, then the reefs and the southern area should return to their 1985 levels of coral cover in 20 years,” Doherty said.
Downgrade from “World Heritage” to “In Danger” likely
Terry Hughes from the Australian Research Council Centre of Excellence for Coral Reef Studies at James Cook University in Townsville agreed: “The solution to starfish outbreaks won’t come from killing them one at a time with a syringe,” referring to the current method of injecting individual starfish with sodium bisulphate to kill them.
Hughes also warned that there is another outbreak of starfish on the horizon, as a result of the 2009 floods. “It’s the fourth in 50 years, and it is far too late to stop it,” he said.
A preview of the AIMS reef monitoring data was seen by a UNESCO team that, last July, warned that the reef was in danger of being downgraded from “World Heritage” listing to “In Danger”. Their major concern was impacts on the southern tip of the reef from port development and liquid natural gas plants, which can affect water quality. UNESCO gave the Australian government a February deadline to come up with a strategic assessment of the potential impact on the reef.
“It’s hard to argue that the universal heritage values of the Great Barrier Reef have not been seriously compromised by losing half of the coral. The “List in Danger” designation is becoming more and more likely,” said Hughes.
The abstract of the paper published in the journal Proceedings of the National Academy of Sciences “The 27–year decline of coral cover on the Great Barrier Reef and its causes”
World Heritage Committee decision on Great Barrier Reef (June 2012), from Tony Burke, Minister for Environment