Parts of the Great Barrer Reef have suffered the highest coral mortality on record, Australian research showed on Tuesday. Scientists fear the rest will suffer a similar fate.
The Australian Institute of Marine Science said surveys of 12 reefs showed up to 72 percent coral mortality, thanks to a summer of mass bleaching, two cyclones and flooding.
In a northern part of the reef, about a third of hard coral had died, the “largest annual decline” in 39 years of government monitoring, the agency said.
Brett Monroe Garner/Getty Images
Often called the world’s largest living structure, the Great Barrier Reef is an expanse of 2,300 kilometers of tropical corals that are home to an astonishing variety of biodiversity.
But repeated mass bleaching events have threatened to rob the tourist hotspot of its wonder, turning the shores of once vibrant corals to a sickly shade of white.
Bleaching occurs when water temperatures rise and the coral expels microscopic algae known as zooxanthellae to survive.
If high temperatures persist, the coral may eventually turn white and die.
This year had already been confirmed as the fifth mass bleaching event on the reef in the past eight years.
NOAA Coral Reef watch
But this latest study also found that a fast-growing coral type – known as acropora – had suffered the highest mortality rate.
This coral grows quickly, but is one of the first to bleach.
Lead researcher Mike Emslie told public broadcaster ABC that last summer was “one of the most severe events” on the Great Barrier Reef, with heat stress levels exceeding previous events.
“These are serious consequences. These are serious losses,” he said.
World Wildlife Fund-Australia oceans chief Richard Leck said initial surveys confirmed his “worst fears”.
“The Great Barrier Reef can recover, but there are limits to its resilience,” he said. “It can’t be hammered this way repeatedly. We are quickly approaching a tipping point.”
Leck added that the area surveyed was “relatively small” and feared that when the full report was released next year, “similar mortality rates” would be observed.
He said the findings reinforce Australia’s need to commit to tougher emissions reduction targets of at least 90 percent below 2005 levels by 2035 and move away from fossil fuels.
The country is one of the world’s largest gas and coal exporters and only recently set goals to become carbon neutral.
