Almost a quarter of the coral on the Great Barrier Reef is now dead, according to two government agencies, with the previously pristine remote northern sections worst affected.

The data from in-water surveys, released on Friday afternoon, was from the two agencies that were part of the national coral bleaching taskforce.

Earlier this week their non-government partner – the Australian Research Council centre of excellence for coral reef studies – released broadly similar data.

Guardian Australia understands the three data sets were planned for release together, but the two government agencies pulled out at the last minute, unhappy with the emphasis of the associated release.

Coral loss as shown in the report of the two government agencies. Photograph: Great Barrier Reef Marine Park Authority/Australian Institute for Marine Science

The media release distributed with the government agency data focused on dispelling perceived exaggerations of the damage, and on the ability of coral to recover, rather than on the size of the environmental disaster.

“Despite reported claims and counter claims over the last month about the ‘death’ of large swathes of the Great Barrier Reef, the true impact of this summer’s major coral bleaching event is now emerging,” it read.

In the release, John Gunn, chief executive of the Australian Institute of Marine Science, said the impacts of the bleaching were still playing out. “And while we know many corals in the northern sector will die, others will recover from bleaching over the coming months and we’re hopeful that in areas where bleaching has been minor the Reef will bounce back well.”

The chairman of the Great Barrier Reef Marine Park Authority, Russell Reichelt, said in the release: “We’ve opted to release results ahead of final completion of surveys because of widespread misinterpretation of how much of the Reef has died.”

Reichelt said 22% of the coral along the length of the reef appeared to be dead.

He said 85% of that mortality was in the region north of Lizard Island, where half the coral had died. In the area immediately to the south – which covers most tourist destinations, including Cairns and Port Douglas – about 16% of the coral had died.



Coral loss on the reef as shown by the two non-government agencies. Photograph: ARC Centre for Excellence in Coral Reef Studies

Below that, mortality was much lower, the report found.

Reichelt said: “We know the Great Barrier Reef, which is larger than Italy, is still resilient with the ability to recover from major events, given enough time.”

The tone of the release was in stark contrast to that released by the non-government partner on Monday, which began: “Mass bleaching has killed 35% of corals on the northern and central Great Barrier Reef according to research conducted by Australian coral reef scientists.”

Despite the overall mortality figures appearing consistent, there were some differences in the mortality figures around particular reefs. The government agencies said Lizard Island had experienced less than 30% mortality, while the non-government survey indicated greater than 50% mortality.

Morgan Pratchett from James Cook University, a member of the taskforce, told Guardian Australia the discrepancy could be a result of different methodologies, or surveys being conducted at different times.

“Take home message is, regardless of whose specific values you believe, the situation is very worrying for the health and functioning of the reef,” Pratchett said. “Fortunately there are major tracts of reef that have been largely spared from the worst effects of bleaching, but there is no denying that we should be very concerned about what the future will hold for the Great Barrier Reef given ongoing climate change.”

A recent study found that on the current warming trajectory, within 20 years the conditions that caused this year’s bleaching would be normal on the reef.