Great Barrier Reef halved since 1985
A new study published in the Proceedings of the National Academyof Sciences today by researchers from the Australian Institute ofMarine Science (AIMS) in Townsville and the University ofWollongong, showed that coral loss was due to storm damage (48%),crown of thorns starfish (42%), and bleaching (10%).
Stop the starfish
“We can’t stop the storms but, perhaps we can stop thestarfish”, says John Gunn, CEO of AIMS. “If we can, then the Reefwill have more opportunity to adapt to the challenges of rising seatemperatures and ocean acidification.”
The findings are based on the most comprehensive reefmonitoring program in the world. The program started broad scalesurveillance of more than 100 reefs in 1985 and from 1993 it hasincorporated more detailed annual surveys of 47 reefs.Researchers have spent more than 2,700 days at sea and theinstitutes have invested in the order of $50 million in thismonitoring program.
Decade of storms
The study shows the Reef has lost more than half its coral coverin 27 years. If the trend continued coral cover could halve againby 2022. Interestingly, the pattern of decline varies amongregions. In the northern Great Barrier Reef coral cover hasremained relatively stable, whereas in the southern regions therewas most dramatic loss of coral, particularly over the last decadewhen storms have devastated many reefs.
The study clearly shows that three factors are overwhelminglyresponsible for this loss of coral cover. Intense tropical cycloneshave caused massive damage, primarily to reefs in the central andsouthern parts of the Reef, while population explosions of thecoral-consuming Crown of thorns-starfish have affected coralpopulations along the length of the Reef. Two severe coralbleaching events have also had major detrimental impacts innorthern and central parts of the Great Barrier Reef.
Recovery takes 10-20 years
“Our data show that the reefs can regain their coral cover aftersuch disturbances, but recovery takes 10-20 years. At present, theintervals between the disturbances are generally too short for fullrecovery and that’s causing the long-term losses,” says Dr HughSweatman, one of the study’s authors.
“We can’t stop the storms, and ocean warming, the primary causeof coral bleaching, is one of the critical impacts of the globalclimate change,” says AIMS CEO, John Gunn. “However, we can act toreduce the impact of crown of thorns,” he says. “The study showsthat in the absence of crown of thorns, coral cover would increaseat 0.89% per year, so even with losses due to cyclones andbleaching there should be slow recovery.
“We at AIMS will be redoubling our efforts to understand thelife cycle of crown of thorns so we can better predict and reducethe periodic population explosions of crown of thorns. It’s alreadyclear that one important factor is water quality, and we plan toexplore options for more direct intervention on this nativepest.”
