Warmer ocean waters have resulted in the largest recorded coral die-off at Australia's Great Barrier Reef, scientists said on Tuesday.
The worst-hit area, stretching 700 km at the northern part of the world's largest coral reef system, has lost about two-thirds of its shallow-water corals in the past eight to nine months, Xinhua news agency cited the Australian Research Council Centre of Excellence for Coral Reef Studies at James Cook University as saying.
"Most of the losses this year have occurred in the northern, most-pristine part of the Great Barrier Reef. This region escaped with minor damage in two earlier bleaching events in 1998 and 2002, but this time around it has been badly affected," said the centre's director, Professor Terry Hughes, who conducted extensive aerial surveys at the height of the bleaching.
Warm waters can force corals to expel or lose algae, calcifying and turning them white.
Scientists expect the northern region to take at least 10 to 15 years to regain the lost corals, but they are concerned that a fourth bleaching event could occur sooner and interrupt the slow recovery, according to the centre.
The southern two-thirds of the reef "escaped with minor damage", said Professor Andrew Baird, who is also from the centre and led teams of divers to re-survey the reefs in October and November.
"On average, six per cent of bleached corals died in the central region this year, and only one per cent in the south. The corals have now regained their vibrant colour, and these reefs are in good condition," he said.
Tourism on the Great Barrier Reef, which covers more than 340,000 sq. km, employs 70,000 people and generates 5 billion Australian dollars in income each year, according to the centre.
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