After conducting comprehensive aerial and underwater surveys, researchers from the ARC Centre of Excellence for Coral Reef Studies are suggesting that mass bleaching has destroyed approximately 35 percent of corals on the northern and central Great Barrier Reef.
Although coral bleaching is a problem that continues to evolve along with climate change, as of now the detrimental process varies greatly when moving from north to south along the length of the reef.
"We found on average, that 35 percent of the corals are now dead or dying on 84 reefs that we surveyed along the northern and central sections of the Great Barrier Reef, between Townsville and Papua New Guinea," said Terry Hughes of the ARC Centre of Excellence for Coral Reef Studies and James Cook University (JCU), who participated in the research. "Some reefs are in much better shape, especially from Cairns southwards, where the average mortality is estimated at only 5 percent.
"This year is the third time in 18 years that the Great Barrier Reef has experienced mass bleaching due to global warming, and the current event is much more extreme than we've measured before," he added. "These three events have all occurred while global temperatures have risen by just one degree Celsius above the pre-industrial period. We're rapidly running out of time to reduce greenhouse gas emissions."
Coral bleaching occurs in abnormal environmental conditions such as the increased sea temperatures caused by global warming. These abnormal conditions cause corals to lose their photosynthetic algae, which leads them to turn white, or "bleach."
If corals can recolonize these algae or temperatures drop to a manageable level, there is a chance of recovery. In the absence of these two processes, the coral may die.
"Fortunately, on reefs south of Cairns, our underwater surveys are also revealing that more than 95 percent of the corals have survived, and we expect these more mildly bleached corals to regain their normal color over the next few months," said Mia Hoogenboom, also from JCU.
The team plans to re-visit the reefs examined in the study over the next few months to determine the final measure of loss that they have experienced from bleaching. Although the team believes that recovery is possible, it is a process that it says will take a decade or longer.
