Selective harvesting in state forests on the NSW North Coast does not adversely affect koala numbers, a three-year research program has found — to the outrage of a forest conservation group.
But the state's peak timber body says the findings vindicate foresters.
As part of the research, which was overseen by the state's Natural Resources Commission (NRC), an independent government body, acoustic sensors were set up in 2019 to monitor koalas in state forests and control sites in national parks.
When scientists from the NSW DPI Forest Science Unit returned after harvest last year, they found no difference in koala numbers.
"We do the work in spring, that's the koala breeding season, and that's when the males bellow to attract females and also to advertise themselves to other males," Dr Brad Law said.
"We put these recorders out at a 400 metre spacing in a grid and we leave them out in the forest for two weeks recording through the night continuously.
"Our sites are very large … about 400 hectares in size, and it varied from site to site, but on average it's about 0.05 koalas per hectare, so that roughly means about one koala per 20 hectares."
Finding horrifies conservation group
The North East Forest Alliance's Dailan Pugh has labelled the finding that logging does not affect koala numbers as "dangerous propaganda" that further threatens the species' survival, and he questions Dr Law's research.
"The recorder will say, 'Yes we have a male koala calling somewhere in the vicinity of this recorder', and that recorder could be over a kilometre away and it doesn't tell you anything about how many koalas there are in the forest," Mr Pugh said.
"They’ve extrapolated that to claim that if you had a koala calling somewhere within a kilometre before an area was logged and they called again somewhere in that vicinity after it was logged, that shows logging has no impact.
"That koala could've been somewhere in an un-logged patch a long way away from where the actual logging occurred, there could've been a whole heap of koalas in that area before and only one after."
The Natural Resources Commission executive director Bryce Wilde has defended the findings from the research program.
"It was guided by an expert panel which we drew together and we had an extensive process to choose the researchers and then quality assured, the work has been extensively peer reviewed and stands up to scrutiny," he said.
Nutritional quality of trees is critical
ANU research fellow Dr Karen Ford sampled leaves from 900 trees of 22 different eucalypt species across nearly 60 sites.
Blackbutt, an important timber species, was found to be one of the lowest nutritional quality species.
"If you alter the tree species composition of the forest by increasing the proportion of koala browse species, then you get an increase in the nutritional quality of the forest, and if you alter it by increasing the amount of blackbutt in the forest than you get a decrease in the nutritional value of the forests for koalas," she said.
The research found that if there were too many non-browse species, there could be a decline in koala numbers in the forest.
Findings 'vindicate' foresters
Timber NSW CEO Maree McCaskill said the findings settled beyond doubt that koalas could co-exist with selective harvesting.
"I'm not saying that the forests are entirely out of the woods by any means … and I think post fires there's still some significant work to be done."
The NRC also found that more research was needed on koalas' response to intensive harvesting practices, and that climate change and the increased risk of wildfires posed greater risks to their long-term survival.
Mr Wilde said the research looked at how koalas were recovering after the devastating 2019-2020 Black Summer bushfires.
"In those areas where the fires were moderately severe, the research is showing there was a reduction in detection rates of some 50 per cent, but that following that koala numbers are returning and there are koalas coming back to those sites."
