Great Barrier Reef Has Lost Half of Its Coral in the Last 27 Years

The Great Barrier Reef has lost half its coral cover in the last 27 years. 

Reasons?
The loss was due to storm damage (48%), crown of thorns starfish (42%), and bleaching (10%), according to a new study published in the Proceedings of the National Academy of Sciences by researchers from the Australian Institute of Marine Science (AIMS) in Townsville and the University of Wollongong.


This finding is based on the most comprehensive reef monitoring program in the world. The program started broadscale surveillance of more than 100 reefs in 1985 and from 1993 it has incorporated more detailed annual surveys of 47 reefs," says one of the program's original creators, Dr Peter Doherty, Research Fellow at AIMS.

"The study shows the Reef has lost more than half its coral cover in 27 years. If the trend continued coral cover could halve again by 2022. Interestingly, the pattern of decline varies among regions. In the northern Great Barrier Reef coral cover has remained relatively stable, whereas in the southern regions we see the most dramatic loss of coral, particularly over the last decade when storms have devastated many reefs. " says Peter Doherty.

Three factors are overwhelmingly responsible for this loss of coral cover:
(a) Intense tropical cyclones have caused massive damage, primarily to reefs in the central and southern parts of the Reef, while population explosions of the coral-consuming Crown-of-thorns starfish have affected coral populations along the length of the Reef. 
(b) severe coral bleaching events have also had major detrimental impacts in northern and central parts of the GBR.

It is possible that the reefs can regain their coral cover after such disturbances, but recovery takes 10-20 years. At present, the intervals between the disturbances are generally too short for full recovery and that's causing the long-term losses. 

The study also shows that in the absence of crown of thorns, coral cover would increase at 0.89% per year, so even with losses due to cyclones and bleaching there should be slow recovery.

Courtesy: ScienceDaily