The Great Barrier Reef, off Australia’s east coast, is the world’s largest and most spectacular reef system, but it’s currently facing a number of dangers that threaten its very existence.
While coral reefs have been shown to have a remarkable ability to bounce back after disturbances, a study published in the journal Science Advances has found that the Great Barrier Reef (GBR) is losing this crucial ability to recover.
Researchers from the University of Queensland, the Australian Research Council Centre of Excellence for Coral Reef Studies and the Australian Institute of Marine Science examined long-term monitoring data from more than 90 of the 2,900 individual reefs that make up the Great Barrier Reef Marine Park.
They found that average coral recovery rates showed a sixfold decline across the GBR over the period 1992 to 2010. Notably, this period did not include the two major back-to-back coral-bleaching events, which devastated the reef in 2016 and 2017.
“This is the first time a decline in recovery rate of this magnitude has been identified in coral reefs,” Juan Ortiz, of the Australian Institute of Marine Science and University of Queensland School of Biological Sciences, and lead author of the study, said in a statement.
The researchers said the decline was driven by a combination of factors, including chronic pressures such as poor water quality and climate change, as well as acute disturbances such as cyclones, coral-eating crown-of-thorn starfish outbreaks and coral bleaching.
Coral bleaching occurs when waters become too warm or acidic, although there are also a number of other triggers. In such conditions, the coral expels the algae living in its tissue, causing it to turn white. Corals don’t necessarily die when they bleach, but they are placed under enormous stress and their mortality risk increases.
Bleaching is a particularly serious threat to reefs across the world, given that climate change driven by human emissions of greeenhouse gases is causing the oceans to become warmer and more acidic—as a result of increased carbon absorption from the atmosphere.
Despite the gloomy situation, researchers emphasized that not all reefs are failing and noted that effective management policies could remedy the situation.
“Our results indicate that coral recovery is sensitive to water quality, and is suppressed for several years following powerful cyclones,” Peter Mumby, of the Australian Research Council Centre of Excellence for Coral Reef Study and the University of Queensland, said. “Some reefs could improve their recovery ability if the quality of the water entering the reef is actively improved.”
Nevertheless, urgent action needs to be taken because the frequency of acute disturbances is only expected to increase, according to the researchers.
“The future of the Great Barrier Reef is threatened without further local management to reduce chronic disturbances and support recovery, and strong global action to limit the effect of climate change,” said Nicholas Wolff, a climate change scieintist at the Nature Conservancy.