Internal Department of Biodiversity Conservation and Attractions (DBCA) documents have revealed the full extent of damage caused by a prescribed burn that felled hundreds of rare native trees along Western Australia's south coast.
Giant red tingles are the largest buttressing species of eucalyptus in the world and only grow in a small parcel of forest 400 kilometres south of Perth, known as the Valley of the Giants.
The trees, which can live for 500 years and reach heights of 80 metres, are considered under threat by global authorities.
But they are targeted as part of WA's controlled burning program that is designed to reduce the bushfire risk across the state's south.
Conservation groups raised the alarm in December last year, after a burn in an area of Walpole-Nornalup National Park known as the Giants Block saw a 400-year-old tingle tree destroyed.
"We have seen a lot of the demise of flora and fauna, and we're very concerned about that," conservationist Bart Lebbing said.
"That is all the tingle on the whole planet."
Most recent fire burned hotter
Immediately after the fire, DBCA stated it was aware of "one large tree" felled by the fire.
But internal documents obtained by the ABC showed 114 trees, including 95 red tingles, were destroyed.
Documents also show the fire burned 99 per cent of the prescribed area with greater severity than mitigation burns conducted at the same block three decades ago.
Crown scorching, where the tops of the trees are visibly damaged and something meant to be minimised during mitigation burns, occurred in more than half of the mature karri and tingle trees in the area.
The DBCA report suggested the severity of the fire could be attributed to higher fuel loads, the intervals since its last burn, ignition timing, and lighting strategies.
DBCA initially declined to release its Prescribed Burn Plan until compelled to do so under Freedom of Information rules.
Despite the damage caused, DBCA said the burn was a success, but several experts contacted by the ABC concluded the burn was a failure.
At a community forum in June, the department confirmed 19 blocks in neighbouring forest were earmarked for burning over the next three years, including four with stands of red tingle trees.
Scientists want reform
The Leeuwin group, a consortium of WA's top environmental scientists, has urged the government to amend its burn program to avoid another mass felling.
"We are really keen to see a form of fire protection put in place that doesn't involve burning blocks of tingle," Professor Steve Hopper said.
"Rather, burns around the periphery of them to afford some protection from incoming fire, but not taking out literally tens if not hundreds of trees.
"That's what we've recommended consistently to the government, and as yet, they haven't responded in a way that indicates a change is afoot."
Department to 'learn' from fire
WA Environment Minister Matthew Swinbourn declined multiple requests from the ABC for an interview.
A statement from his office said DBCA had a legislated responsibility to protect communities and the environment from bushfires and defended the department's management of its burn program.
"DBCA follows specific operational guidelines that include scrub rolling, clearing, hosing, and applying fire retardant to the base of tingle trees to protect large hollow trees and prevent canopy fires during prescribed burns," it read.
“The prescribed burning of red tingle forests follows scientific evidence and operational best practice.
"DBCA continues to assess and learn from all events."
An earlier statement said the burn program was based on 60 years of data, with new research underway.
However, the Leeuwin group said the minister's response amounted to a red herring.
"The minister's solution has been to park it for 10 years, and he's given the department a bit of money for new research to be done," Professor Hopper said.
"We think the scientific evidence is already compelling."
A trial burn of the same plot in 1997, conducted by the then Department of Conservation and Land Management (CALM), found that 10 trees per 100 hectares was the highest acceptable loss.
DBCA's assessment of the Giants Block burn identified 114 trees in a 91-hectare area as having fallen, well in excess of the CALM report.
'It's only going to get worse' says ecologist
Ecologist and lecturer at the University of Tasmania, Nathan Anderson, has been studying red tingles in the south-west for the past five years.
He said some historical data, like the 1997 CALM report, was being ignored.
"The previous burn that was in there, there were 30 trees that collapsed, that was a concerning loss of trees, and we're at more than three times that amount for the same area," he said.
"We're looking at a concern that was raised in the 1990s, and it's still a concern today, and if we don't address that, then it's only going to get worse."
Mr Anderson said continued burning in the tingle forest would only serve to weaken existing trees and increase the risk of future collapse.
Mr Anderson said that as the climate in the south-west changed, so too should fire mitigation practices.
"In the next five decades, we're looking at the entirety of the red tingle forest becoming drier than the driest portion of red tingle now," he said.
"There needs to be an open acknowledgement that this is a fire-sensitive ecosystem, then we can move forward with that with discussions from ecology, from fire practitioners, from fire science within the department."
