Thousands of years of accumulated leaf fall makes the ground bounce like a mattress underfoot and, high above, rainforest coachwood trees form a dense canopy that dresses the understory in permanent shade.
Some of the unique plants in this rainforest can trace their lineage back 40 or 50m years when the Gondwana supercontinent was breaking apart and Australia was detaching itself from what is now Antarctica.
Take only a few steps from the cool shade and you emerge to something altogether different. Still rainforest, but changing fast.
Soil and rocks are exposed and, above, the leafless branches of tall and dead trees let the sunlight strike the forest floor.
This is a place packed with threatened species, including the nightcap oak – a true Gondwanan relic that grows nowhere else.
On the ground and at the base of the thin-barked trees is charcoal. Five years ago, chunks of this rainforest not evolved to burn, did burn, during what became known as Australia’s black summer bushfires.
“It can take a lot of these trees a long time to die. It is a long, slow death,” says Dr Robert Kooyman, an evolutionary ecologist who has spent more than 40 years working and studying the rainforests in and around Nightcap national park in northern New South Wales.
About 73,000 sq km of forest were burned in the east and south of the country during black summer and the fires scorched the habitat of about 3 billion native animals.
Half of the world heritage-listed Gondwana rainforests – a network of 40 parks and reserves – were affected by the fires that were driven by global heating. Fires burned into about 10% of the rainforest in the Nightcap area and affected about 30% of the rainforest’s margin, says Kooyman.
Kooyman discovered the nightcap oak in the late 1980s. Unlike Australia’s many eucalypt species, rainforest trees have not evolved to deal with fire.
“It burns around the base and it cooks the cambium layer – the live wood – and the bark. It triggers this slow-motion death and you can see the progressive stages here,” he says, pointing to trees in various stages of that slow death.
The fires killed about a third of the mature nightcap oaks, he says, leaving 181 behind. Kooyman’s monitoring shows 72 of those are struggling to survive, or have lost their main stem and now persist “as suckers only”.
“That one’s on the way out,” says Kooyman, pointing to a nightcap whose bark and stem is split and is covered by fungi.
“That one is failing too,” says Kooyman, pointing to another. “And this was a low-intensity burn.”
‘This is not recovery’
There is smoke in the air from a nearby hazard reduction burn on the day Kooyman takes us to the marked-out plots where he and colleagues are monitoring every post-fire breath, death and revival.
Traps made from net and laundry baskets catch and record whatever falls from the canopy; straps called dendrometers measure trunk growth; and then there are recordings of temperature, humidity, light and seed generation, and the state of the soil.
“They can shrink before they die,” says Kooyman, pointing to one of the dendrometers. “The theory of negative growth is real – that would drive the economists crazy,” he laughs.
As we leave to look at another patch of burnt rainforest, Kooyman yanks a young wattle that’s sprouting.
The fires removed the leaf litter on the forest floor, creating a perfect bed for dormant wattle seeds to germinate. They have been growing at an incredible density – as many as 30,000 a hectare (12,100 an acre).
“They’ll create a fire influence inside the rainforest,” he says. “If we had a dry season and another fire, there are huge amounts of this vegetation that would explode in flames. That’s the problem. You end up with a fire-prone landscape.”
The fires here were followed within months by torrential rain and violent floods that blasted the banks of the rock-strewn creeks and swept away weakened trees and plants. Kooyman used to see platypus here but since the fires, there’s no sign.
More than once on this day, Kooyman bristles when the word “recovery” comes up. For fire-adapted forests, the word “recovery” might be fair, but not for rainforests, he says.
“Let’s not let this terminology overwhelm us. This is not recovery,” he says, pointing to a 2ft-tall sucker growing from the base of a dead trunk.
“What we have discovered is that even after almost five years, the trajectory is still in reverse. The impacts are accumulating and it hasn’t stabilised.”
“Do we want these forests in the future? Do we log them? Do we have them crisped by climate change, or do we start compensating for what we know is happening and protect them?”
Measuring decline
The fire that hit Nightcap national park and the neighbouring Whian Whian state conservation area started in late October as a lightning strike and gained momentum as the extreme heat and dry of 2019 was joined by winds.
Kooyman is an honorary research fellow at Sydney’s Macquarie University, a researcher at the city’s Royal Botanical Gardens and scientist with Missouri Botanical Gardens programs in west Africa and Madagascar.
But he lives less than an hour’s drive from Nightcap and got to his beloved rainforest within days as the ground was still smouldering.
“I did find myself, not depressed but, maybe like PTSD working in these impact zones. I’m not inclined to any level of depression, but this has had an impact on me. You catch yourself being a little angrier or shorter [tempered] than usual.
“Having never lived through these sorts of events at those scales it takes some adjusting.”
Kooyman is 71, but he moves like someone half his age. Several times this morning, he jumps from his four-wheel drive to chainsaw trees that have fallen across the track.
“I’m feeling an urgency now and it’s not so much down to my sunset clause,” he says.
In a break, he puts his laptop on the bonnet to show some images of his plots.
They look like landscape ink drawings of the forest you might hang on your wall. But these delicate strokes are the artefacts of data from laser scans of the parts of the forest he’s been monitoring.
The areas that escaped the fire have a dense and continuous canopy shrouding the understory. But the scans taken from areas that burned show a canopy that is barely a canopy at all.
Technology is moving fast and Kooyman is excited that new approaches, like LiDAR scanning, could give him answers to questions he has been chasing his whole career.
“We’re getting deeper insights into how these rainforest systems work. So I’m excited,” he says.
“But the irony is we’re getting better at measuring decline.”
