An unprecedented amount of coral bleaching for two consecutive years has severely damaged two-thirds of Australia’s Great Barrier Reef, aerial surveys have shown.
Scientists at the ARC Centre of Excellence for Coral Reef Studies recorded severe coral bleaching for the second time in 12 months after surveying the Great Barrier Reef’s entire 2,300km-long (1,500) miles ecosystem.
“This is the fourth time the Great Barrier Reef has bleached severely – in 1998, 2002, 2016, and now in 2017. Bleached corals are not necessarily dead corals, but in the severe central region we anticipate high levels of coral loss,” said Dr. James Kerry of James Cook University.
“It takes at least a decade for a full recovery of even the fastest growing corals, so mass bleaching events 12 months apart offers zero prospect of recovery for reefs that were damaged in 2016.”
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The study found that while the northern third of the reef experienced the most severe bleaching last year, the middle third experienced the most intense coral bleaching this year, resulting in catastrophic damage of the natural wonder of the world.
“The combined impact of this back-to-back bleaching stretches for 1,500km (900 miles), leaving only the southern third unscathed,” said Prof. Terry Hughes who undertook the aerial surveys in both 2016 and 2017.
“The bleaching is caused by record-breaking temperatures, driven by global warming. This year, 2017, we are seeing mass bleaching, even without the assistance of El Niño conditions.”
The 2017 survey of the reef covered more than 8,000km (5,000 miles) and nearly 800 coral reefs that matched the 2016 aerial surveys. Last year, Climate Central found bleaching has hit 93 percent of the reef, with 80 percent enduring severe bleaching.
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The mass bleaching, coupled with the destructive Tropical Cyclone Debbie in March, has struck a previously undamaged section of the reef.
“Clearly the reef is struggling with multiple impacts,” explains Prof. Hughes. “Without a doubt the most pressing of these is global warming. As temperatures continue to rise the corals will experience more and more of these events: 1°C of warming so far has already caused four events in the past 19 years.”
“Ultimately, we need to cut carbon emissions, and the window to do so is rapidly closing.”