Half Of GBR Corals Gone in Past 27 Years; Study Projects 90% Loss Under BAU Scenario
The coverage of living corals on Australia's Great Barrier Reef could decline to less than 10 percent if ocean warming continues, according to a new study that explores the short- and long-term consequences of environmental changes to the reef.
Environmental change has caused the loss of more than half the world's reef building corals. Coral cover, a measure of the percentage of the seafloor covered by living coral, is now just 10-20 percent worldwide. The Great Barrier Reef, once thought to be one of the more pristine global reef systems, has lost half of its coral cover in only the last 27 years. Overfishing, coastal pollution and increased greenhouse gas emissions leading to increased temperatures and ocean acidification, as well as other human impacts are all affecting the delicate balance maintained in coral reef ecosystems.
Now, in a new study that aims to project the composition of the future Great Barrier Reef under current and future environmental scenarios, researchers found that in the long term, moderate warming of 1-2 degrees Celsius would result in a high probability of coral cover declining to less than 10 percent, a number thought to be important for maintaining reef growth. In the short term, with increasing temperatures as well as local human-made threats like coastal development, pollution, and over-fishing, the study found that corals--tiny animals related to jellyfish--would be over-run by seaweed which would, in effect, suffocate them. In the longer term, interactions among reef organisms would lead to dominance by other groups, including sponges and soft corals known as gorgonians.
The study, now in pre-print online in the journal Ecology, uses a multivariate statistical model and includes quantitative surveys of 46 reef habitats over 10 years of data from 1996-2006. "The model indicated that warming of an additional 1-2 degrees Celsius would more than likely lead large declines in coral cover and overall changes to the community structure," said lead author Jennifer K. Cooper, a graduate student in marine biology at James Cook University. "If our model is correct the Great Barrier Reef will begin to look very different as ocean temperatures increase."
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