Great Barrier Reef coral loss dates back almost a century

A study by researchers from the University of Queensland has revealed that fatal changes in coral communities on the Great Barrier Reef began almost 100 years ago. Researcher Dr. Tara Clark explained that corals are highly sensitive to environmental change and that close observation is needed to avoid irreparable damage to the health of this ecosystem.

“Hard coral cover on the Great Barrier Reef is on a trajectory of decline,” said Dr Clark. “Yet, little is known about past coral mortality before long-term monitoring began around the 1980s to give us a long-term picture of what has happened since European colonization of the coast.”

Before the 1980’s, there was limited baseline information on the dynamics of corals. This has made it challenging for scientists to understand the recent trends. Dr. Clark’s team used “high-resolution uranium-thorium dating, modern and palaeoecological techniques” to examine more about the history of corals in Australia’s Palm Islands.

“At a regional scale we found a loss of resilience in ecologically important branching Acropora corals – formerly dominant key framework builders – with recovery severely lagging behind predictions.”

The study found that the Acropora coral death occurred simultaneously among reefs in the Palm Islands and coincided with extreme weather events. Bleaching and flooding put too much strain on the corals in the 1920’s to 1960’s and again in the 1980s to 1990s.

“Surveys conducted in 2014 revealed low Acropora cover – less than five per cent – across all sites, with very little evidence of recovery for up to 60 years at some sites, thus there was little left in this region for the 2016 bleaching event to kill,” said Dr.Clark.

Combined with previous research, the results of this study suggest that the underlying condition of the Great Barrier Reef had already degraded before long-term monitoring began in the 80s. The discovery of this undocumented coral loss means that overall fatality in the region is the likely far worse than previously reported.

The analysis reaffirms the urgent need to reduce human impacts on coral reefs in order to buy time for the reefs to recover before the next major disturbance event.

“The findings of this study will also prove valuable to reef managers by providing a reliable baseline for ongoing monitoring and identifying reefs at risk for deterioration, especially for those where modern observations are lacking,” said Dr. Clark.

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By Chrissy Sexton, Earth.com Staff Writer

Image Credit: M. Prazeres