Coral decline in Great Barrier Reef 'unprecedented'

Reef monitoring program shows northern section has lost half of its coral cover

A steep decline in coral cover right across the Great Barrier Reef is a phenomenon that "has not been observed in the historical record", a new report by the Australian Institute of Marine Science says.

The institute, Australia's government-backed marine research agency, periodically releases results of a long-term reef monitoring program. Each reef along the Queensland coast is visited by researchers every two years to assess its condition and coral cover.

The latest results, released on Tuesday, detail how major bleaching events in 2016 and 2017 have impacted on different sections of the reef. AIMS said it had no previous record of bleaching events occurring in successive years.

"Over the 30-plus years of monitoring by AIMS, Great Barrier Reef reefs have shown their ability to recover after disturbances, but such 'resilience' clearly has limits," the report says.