It's the second time in only 12 months scientists have recorded mass bleaching in the reef after aerial surveys.
The Great Barrier Reef of Australia that experienced an unprecedented bleaching past year has now been struck by another bleaching event.
The latest damage is concentrated in the middle section, whereas last year's bleaching hit mainly the north.
The aerial surveys in 2017 covered more than 8,000km and scored almost 800 individual coral reefs closely matching the aerial surveys in 2016 that were carried out by the same two observers. Scientists have found an astonishing two-thirds of the reef undergoing mass coral bleaching as warmer ocean temperatures are basically boiling them to death.
The recent cyclone Debbie that hit the Australian region in March this year has also caused considerable damage to the healthy parts of the reef. Terry Hughes, Director of the ARC Centre of Excellence for Coral Reef Studies, who conducted the aerial surveys of the reef. The reef, a UNESCO World Heritage Site, suffered heavy bleaching in 2016 in its northern third as the El Nino weather event shifted warm waters in the Pacific.
Bleached corals can recover if the temperature drops and algae can recolonize.
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"There is a rapidly closing window where we still have the opportunity to address this issue". But this time the bleaching has occurred for two years in a row, first in 2016 and again this year which has affected two-thirds of the reef! "As such, they are indicators of the increasing pressure that humans exert on ecosystems on the regional and global scale". "The Australian government has launched an unprecedented effort to invest more than A$2 billion ($1.5 billion)... in a Reef 2050 plan, which we're 18 months into", said Josh Frydenberg, Australia's Minister for the Environment and Energy.
The bad news for Australia's Great Barrier Reef just keeps on getting worse.
Bleaching occurs when elevated sea water temperatures cause corals to turn white by expelling the colorful algae, called zooxanthellae, that live within corals and use photosynthesis to provide nutrients for themselves and their hosts. "Last year was bad enough, this year is a disaster year", Brodie said. The fastest-growing species of corals may take at least 10 years to make a decent recovery, while slower-growing corals may take far longer. Hughes, warned that as bleaching events occur in back-to-back years, recovery will be nearly impossible in some regions.
"The central third this year, I would say, was as severe in terms of bleaching as what we saw as the northern third last year", he said.
Australia's Minister for the Environment and Energy Josh Frydenberg said in a statement that climate change was the "number one threat" to the Great Barrier Reef.