Unprecedented coral bleaching in consecutive years has damaged two-thirds of Australia's Great Barrier Reef, aerial surveys have shown. 

航空勘测发现，近年连续发生的珊瑚白化问题空前严重，澳大利亚三分之二的大堡礁已遭到重创。

The bleaching - or loss of algae - affects a 1,500km (932 miles) area of the reef, according to scientists. 

The latest damage is concentrated in the middle section, whereas last year's bleaching hit mainly the north. 

Experts fear the proximity of the two events will give damaged coral little chance to recover. 

Prof Terry Hughes, from James Cook University, said governments must urgently address climate change. 

"Since 1998, we have seen four of these events and the gap between them has varied substantially, but this is the shortest gap we have seen," Prof Hughes told the BBC. 

"The sooner we take action on global greenhouse gas emissions and transition away from fossil fuels to renewables, the better."