Great Barrier Reef coral halved by bleaching, climate change, report finds.

 Extract from ABC News

ABC Tropical North

By Myles Houlbrook-Walk and Ollie Wykeham

Posted Yesterday at 4:15pm, updated Yesterday at 5:37pm

The Great Barrier Reef suffered mass coral bleaching events in 2016, 2017 and 2020.(Supplied: Andreas Dietzel)

The Great Barrier Reef has lost more than half of its corals since 1995, according to a new Australian Research Council (ARC) report.

Key points:

• A study by James Cook University scientists shows the Great Barrier Reef had declined by 50 percent since the mid-1990s
• Small, medium and large coral populations have all declined, largely because of bleaching events

• The lead author of the study said the impact of bleaching in 2020 is not yet known

The ARC Centre of Excellence for Coral Reef Studies research showed the reef's small, medium and large coral populations had all declined over the past three decades, largely due to bleaching events in 2016 and 2017.

Lead author Andreas Dietzel said the main cause of coral death was human-induced climate change.

"We can clearly correlate the rising temperatures to coral mortality and bleaching on the Great Barrier Reef," he said.

Mr Dietzel said the impact of bleaching in 2020 still had not been accounted for and the overall picture of the reef's health could be worse than the current evidence suggested.

"We've had large-scale bleaching events in 1998 and 2002, but they were absolutely dwarfed by the more recent ones in 2016 and 2017," he said.

"The decline occurred in both shallow and deeper water, and across virtually all species."

Mr Dietzel said the bleaching in 2016 and 2017 had impacted some sections of the reef more heavily than others.

"The picture that we saw, especially in the far north, was quite devastating," he said.

Mr Dietzel says the ecosystem is likely to continue to change significantly.(Supplied: Great Barrier Reef Marine Park Authority)

Full impact not yet known

Mr Dietzel, who is completing a PhD on reef observations, says the signs of reef degradation are being ignored, especially by some politicians.

"It's very frustrating to see that there's not much done," he said.

"In many cases it's even denied that it happens at all."

Mr Dietzel said the reef, already markedly different to what it was 30 years ago, would continue to change.

"I think the most likely scenario is that we'll see a complete change in the species that we'll see there," he said.

"Possibly the fish life as well, and just much poorer communities of corals and other reef organisms." 

Mr Dietzel says the health of the reef may be worse than the report indicates.(Supplied: Andreas Dietzel)

Looking to the future

Mr Dietzel said the future of the reef was by no means guaranteed.

"There's some scientists who give it another 10, 20 years," he said.

"But it's very difficult to say at this stage.

"Reefs always go through periods of disturbance then recover.

"Recovery will ultimately depend on whether we'll see further disturbances like mass bleaching events or cyclones as well."

Government highlights 'unprecedented investment'

In a statement, a spokesperson for the Federal Department of Environment said the research added to the body of scientific evidence identifying the challenges faced by the reef:

"The Morrison Government supports and funds research through the ARC Centre of Excellence for Coral Reef Studies and the findings reinforce the Australian Government's commitment to global action on climate change through the Paris Agreement and through new energy technologies, and to its support for the resilience of the Reef through the Reef 2050 Plan.

"The Reef 2050 Plan, jointly developed with the Queensland Government is the centrepiece of Australia's Reef protection efforts.

"Its focus is on supporting the Reef’s health and resilience in the face of climate change by reducing local and regional pressures.

"The Australian and Queensland governments are investing more than $2.7 billion from 2014-15 to 2023-24 to implement the Plan. Of this, more than $1.9 billion is being invested by the Morrison Government – an unprecedented investment."