The Great Barrier Reef loses half its coral in three decades

Half of the corals on the Great Barrier Reef have been lost over the past 30 years and it may struggle to recover from widespread bleaching, a new study has found.

The record temperatures that triggered mass bleaching in 2016 and 2017 resulted in fewer small, baby corals and breeding adult ones, Terry Hughes, professor at ARC Centre of Excellence for Coral Reef Studies at James Cook University in Queensland, said.

"The decline occurred in both shallow and deeper water, and across virtually all species—but especially in branching and table-shaped corals," he said.

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The corals support life on the reef including its many types of fish.

But the loss of this habitat has seen a reduction in fish numbers.

Climate change is behind the rise in events, such as heatwaves, that are disturbing the life of coral reefs.

The study shows alarming reductions of coral colonies in the Northern and Central Great Barrier Reef after the mass coral bleaching in 2016 and 2017.

The southern part of the reef was also exposed to record-breaking temperatures early this year.

The size of the reef can no longer be counted on to protect it, the researchers warned.

"We used to think the Great Barrier Reef is protected by its sheer size - but our results show that even the world's largest and relatively well-protected reef system is increasingly compromised and in decline," Professor Hughes said.

The study calls for better data on the demographic trends of corals.

"There is no time to lose - we must sharply decrease greenhouse gas emissions ASAP," the authors said.