The conservation outlook of the Gondwana rainforests of Australia's east coast has deteriorated in the wake of the Black Summer bushfires.
This was the conclusion of the World Heritage Outlook, which the International Union for Conservation of Nature released on Thursday.
The report changed the conservation outlook of the Gondwana rainforests from "good with some concerns" in 2017 to "significant concern" in 2020.
Ancient world heritage areas exist in large forests from the Barrington Tops to the Gold Coast.
They are the last remnants of the supercontinent Gondwana, which broke up about 180 million years ago.
Usually these forests are too wet to burn, but 54 per cent of the NSW parts of the Gondwana world heritage areas were within the fire grounds of the 2019-20 bushfires. The most affected ecosystems were rainforests.
About 10 per of the Barrington Tops National Park world heritage area was damaged in the fires. The area of affected rainforest - which is part of the ancient Gondwana system - covered 4011 hectares.
Thursday's report received international attention, as it was compiled by the official advisory body on nature to the UNESCO World Heritage Committee.
North East Forest Alliance spokesman Dailan Pugh compared the threat of rainforests burning to the bleaching of coral on the Great Barrier Reef.
"We're in big trouble," Mr Pugh said.
"They've identified the Great Barrier Reef as in dire straits. It's amazing that such an international icon is collapsing before our eyes. Our rainforests are under a similar growing threat.
"They call it the Black Summer, but a lot of the fires were in spring."
A NSW government report found that 37 per cent of the state's rainforests were affected by the fires.
"That's just horrifying. Rainforests generally don't burn," Mr Pugh said.
Ecologist Mark Graham, who has studied the Gondwana rainforests for decades, said the burnt areas were not recovering in some places.
"There are substantial swathes of a number of these Gondwana heritage properties where there really is no recovery," Mr Graham said.
In these places, he said, "the forests are utterly silent".
"There are just the frames of a former ecosystem. This isn't across all the fire grounds. But within a significant number of the fire grounds, these world heritage values have been effectively lost," he said.
"I can only profess to have spent time in the mid-reaches of the Gondwana rainforests around Coffs Harbour, Armidale and towards Grafton."
He said the Gondwana forests had been eroded, but there were "unburnt areas in the core areas of Gondwana that have not been really badly compromised".
"The Barrington Tops was essentially the least impacted, which is really great for the health of that southern big block of Gondwana."
Mr Graham said active management of the Gondwana forests was needed "into the future".
"Management of weeds and trying to keep fire out of these amazing ancient forests as best we can - we've got to do that," he said.
"There's a lot that can be done that can hopefully shift the trajectory."
If the trajectory continues, Mr Pugh said "our rainforests and half our biodiversity are under threat".
He said the rainforests were "so important".
"They have such a long lineage. We're at risk of seriously degrading and diminishing their biodiversity. It's not looking very good," he said.
"We're meant to be having a wet year this year, so we'll probably dodge a bullet. But you've got Fraser Island burning at the moment and other world heritage sites. It's really scary."
The World Heritage Outlook report said the most prevalent threats to natural world heritage sites were "invasive alien species and climate change".
The report said climate change "continues to affect more and more natural world heritage sites".
"Climate change is associated with increasing frequency and severity of fires, as was exemplified by some sites which have faced unprecedented fires in 2019-2020, such as Gondwana Rainforests of Australia and Pantanal Conservation Area [in Brazil]."
In 2010, the National Parks and Wildlife Service predicted in its Barrington Tops plan of management that climate change was "one of the greatest potential threats to the values" of the area.