Scientists have compiled a new global database of coral reef mass-bleaching events that shows the likelihood of bleaching increased eight-fold from the late 1990s.
The new database includes 80 per cent more reports of coral bleaching than the existing databank, with Australia having the second-worst record.
It also demonstrates the relationship between higher water temperatures and bleaching.
The database was put together by three researchers from Canada and Australia who personally contacted scientists and divers from around the world, and trawled thousands of research papers to bring it together.
Simon Donner, climate scientist from the University of British Columbia and the lead author, said they had created the “most comprehensive historical database of reports of coral bleaching from around the world”.
“The largest number of reports actually comes from the Caribbean, and part of that is due to the extensive bleaching event that happened in 2005 and then again in 2010,” he said.
“After that the largest number of reports comes from Australia and the Great Barrier Reef.”
The scientists’ work, published in the journal Plos One, has almost doubled the existing database of mass coral-bleaching events around the world.
It has linked higher water temperatures to an eight-fold increase in the likelihood of bleaching from the late 1990s.
“There’s so few records before even 1990 and that’s not because there were no scientists studying reefs or that people weren’t diving, it’s because bleaching events were not happening very often,” Professor Donner said.
“We have this database from time zero up to 1990 [and] there’s only about 250 records – then after that there’s another 7000-plus.”
Once vibrant reefs ‘now graveyards’
The new database has been welcomed by the Australian Research Council Laureate Fellow, Professor Ove Hoegh-Guldberg from the University of Queensland.
“I’m personally very interested in that because it’s an ability to get baseline and the amount of change,” he said.
“And then hopefully identify areas that might be more robust than others to the climate change coming along.
“If we can identify those, we can then really focus our attention on making sure that they get through to the Paris agreement conditions – stabilise temperatures by mid-century.
“It’s really important that we get this sort of information.”
Professor Hoegh-Guldberg recently examined reefs around the Maldives Islands, after doing a baseline survey two years ago and said what he found was shocking.
“The amount of coral that’s been lost across vast parts of that archipelago system – reefs that were vibrant, full of fish, full of coral, are now graveyards,” he said.
“And, it’s not just in one or two places, it’s across most of the archipelago.
“It’s a really serious indicator of this new climate regime that we seem to have entered.”