A new study has found that higher water temperatures have ravaged the Great Barrier Reef, causing the worst coral bleaching recorded by scientists.
In the worst-affected area, 67% of a 700km swath in the north of the reef lost its shallow-water corals over the past eight to nine months, the Australian Research Council Centre of Excellence for Coral Reef Studies based at James Cook University study found.
"Most of the losses in 2016 have occurred in the northern, most-pristine part of the Great Barrier Reef," Prof Terry Hughes said. "This region escaped with minor damage in two earlier bleaching events in 1998 and 2002, but this time around it has been badly affected."
The southern two-thirds of the reef escaped with minor damage, Hughes said. This part was protected from the rising sea temperatures because of cooler water from the Coral Sea.
Scientists expect that the northern region will take at least 10 to 15 years to regain the lost corals but are concerned a fourth bleaching event could interrupt the slow recovery.
The dire assessment of the reef's health comes as the Australian government is due to report to Unesco's world heritage committee on its handling of the reef.
After the federal government submits the report Unesco will decide whether to again consider listing the Great Barrier Reef on its âlist of world heritage in danger.
The government will need to report on how it has funded and implemented its Reef 2050 long-term sustainability plan, as well as how the bleaching event has affected the reef.
Since it last considered including the Great Barrier Reef on its list, the reef has undergone the worst bleaching event in recorded history. According to government agencies, 22% of the reef was killed in one hit, as unusually warm waters bleached and killed the coral.
Climate change poses such a threat to the reef that the former head of the Great Barrier Reef Marine Park Authority has called for a ban on all new coalmines in Australia to protect the reef from climate change.
Graeme Kelleher, who was the first chief executive of the authority, a position he held for 16 years, said: "Australia cannot have a healthy Great Barrier Reef and a continuing coal industry."
"I love the reef and I have worked to preserve it since 1979; I will oppose anything that threatens to destroy it," he said.