To learn all she could about tall trees, Lauren Fuge talked to a range of experts – then strapped on a harness and scaled an 80 metre blue gum.
I’m standing at the base of Lathamus Keep, watching tree climber and photographer Steve Pearce attach my harness to an orange rope no thicker than my finger. It’s one of four climbing lines he and his crew have set, using light lines attached to weighted throw bags – an impressive mission when the first branch is 25 metres up. The tree’s moss-patterned trunk is a wall of wood before me, twice as wide as my outstretched arms. I squint into the January-bright canopy.
“How far up are we going?” I ask.
“The line’s set at 70 metres,” Pearce says, with the casual tone of a person who has spent thousands of hours aloft.
“And how tall’s the tree?”
“Eighty metres. Biggest blue gum in the universe.”
Biggest blue gum (Eucalyptus globulus) in the universe, roughly the size of the launch structure of NASA’s Artemis Moon mission, and it’s just an hour and a half from nipaluna/Hobart.
“This forest is called the Grove of Giants,” explained the endlessly enthusiastic canopy ecologist Dr Jen Sanger, as she led me through the dappled dreamscape of wet eucalypt forest that morning. “There’s about 150 trees here over four metres in diameter, so it’s just jam packed with giant old trees.”
The forests of lutruwita/Tasmania are one of just three places in the world where trees grow above 80m. In the teeming rainforests of Borneo, yellow meranti trees soar up to 100m; the fog-shrouded west coast of North America creates the perfect conditions for temperate rainforest species to reach even more epic proportions; here, five species of eucalypt shoot up above the smaller rainforest trees to become islands in the sky.
This giant, Lathamus Keep, is named for the habitat it provides the endangered swift parrot (Lathamus discolor). Its deeply furrowed buttress resembles giant fingers driving tip-first into the soil; lanky saplings shoot up out of the gnarly metacarpals, their roots gripping onto knuckles for structure.
It’s circled by decay: dropped leaves and broken branches and strips of shed bark longer than I am tall, make the surrounding trees look like they’re dripping with candlewax.
I’ve spent hundreds of hours walking through forests before – I consider myself a tree person. But I often ignore them. They’re everywhere, every day. Yet in the kaleidoscope of information relayed to my brain every millisecond, trees usually don’t make the cut. And I’m not alone: US botanists coined the term “plant-blindness” to describe this inability. It’s not universal, but it’s a real phenomenon for a great chunk of us humans.
Right now, I’m the least plant blind I’ve ever been. I attach my foot ascender to the climbing line and shift my weight off the ground. Suspended, gently spinning, it’s impossible not to pay full attention to this living, breathing being. My life now depends on it.
“If you were an alien, coming to Planet Earth, the first thing you’d probably notice is that there’s a lot of water, because it’s blue,” says Margaret Barbour, a plant physiologist at the University of Waikato in Aotearoa New Zealand. “And the second thing you’d notice is that on land, it’s green.”
With four billion hectares of forest around the world, trees are “the Earth’s chief way of being”, in the words of author Richard Powers. Some 380 million years ago, as the first tetrapods crawled up out of the swamps onto dry land, trees shot up from ankle-brushing plants into 30m giants. While our ancestors worked out how to breathe with primitive lungs, trees rapidly rose to the status of gods. The first forests transformed the planet, becoming the dominant drivers of the biogeochemical cycles that run all life on Earth – carbon, water, nitrogen, phosphorous.
We were looking at the tree canopy – so many epiphytes, so many animals. A student said, “Funny! Man is able to collect stones on the Moon but unable to work in the canopy”.
Trees also inherited the gift of photosynthesis first developed in stromatolites 3.4 billion years ago: their leaves take in carbon dioxide and light from the atmosphere to power their growth. This not only modifies the atmosphere by releasing oxygen, but provides habitats for animals and forms the basis of everything we eat.
“That, I think, is the magic of plants – they can convert radiant energy and CO2 into a stored energy that all life depends on,” Barbour tells me. “That’s something we learn in primary school, but it still has that magic.”
Up, up, up, into free space, watching the thick, textured bark turn smooth and creamy as I climb, feeling like I’m closing an evolutionary loop. My foot ascenders slide easily along the rope then catch, allowing me to step up as if on a rope ladder. But the act of climbing isn’t easy at all: every seven or eight vertical metres, muscle fatigue forces me to stop and rest, swinging gently over the world.
Today, humans are the only primates that don’t spend time in trees. Some six million years ago, our ancestors moved down onto the grassland savannahs for the first time, where their postures straightened and their knees and feet grew better suited for walking than canopy-swinging. Their world flattened, and became ours. The years ticked past; the canopies remained out of reach. Botany boomed briefly, clipping and classifying the forests Linnaean-style, then science moved onto more sensational ambitions: the deep ocean, the frozen poles, infinity and beyond.
In Richard Preston’s 2007 book The Wild Trees, French botanist Francis Hallé recalls walking through the rainforests of New Guinea with students in the 1970s. “We were looking at the tree canopy – so many epiphytes, so many animals,” Hallé says. “A student said, ‘Funny! Man is able to collect stones on the Moon but unable to work in the canopy.’”
In those early days, researchers tried to collect data using blimps, aircraft, and cherry pickers with buckets to lift them up into the treetops.
“The French even designed a massive hot air balloon that has this platform that lies on top of the canopy,” explains Sanger, who came to the field in the 2010s to study Australia’s subtropical rainforest canopies. “It’s got these holes in it so you can…walk around and just stick your hand down in the hole and grab some leaves to sample.”
One of the first to use a direct climbing method – using just your body and ropes –was US scientist Meg Lowman. As a young PhD student in 1970s, Lowman came to Sydney to study tree dieback in northern NSW. “She met a whole bunch of cavers, and they helped her get up into the trees,” Sanger says.
In the canopy, Lowman discovered the root cause of the dieback: surging populations of insects in response to the warming, drying climate.
In the decades since, direct climbing has become the least invasive and most economical option for canopy science, but still these trees remain hard to access, especially the temperate-forest giants whose first branches are often dozens of metres up. It wasn’t until the 1990s – 40 years after Hillary and Norgay clambered to Everest’s summit, and a quarter of a century after Armstrong stepped onto the Moon – that US botanist Steve Sillett discovered the world of redwood canopies in California.
That, I think, is the magic of plants – they can convert radiant energy and CO2 into a stored energy that all life depends on.
No one looked at the canopy biodiversity of southern Australia’s giant eucalypts until the early 2000s, when US-trained masters student Yoav Daniel Bar-Ness trapped and surveyed their insect life.
Very little work has been done here since. When Sanger and her husband Pearce began documenting and measuring Tasmania’s tall trees in 2015, they were among the first to return to these canopies in a scientific capacity.
And yet, our bodies still hold memories of our ancestors’ arboreal lives. My hands grip the rope with opposable thumbs that stuck in our evolutionary line because they’re useful for grasping branches. My eyes pick out the purple of Sanger’s jumper against undulating green and brown, thanks to an extra type of light-sensitive cell useful for spotting ripe, colourful fruit – a trick of the forest to distribute its seeds. We were shaped by forests for millennia before we became Homo sapiens. My muscles may have forgotten how to climb, but this isn’t a journey into the unknown: it’s a return.
Just below Lathamus Keep’s first branch, I sit back in my harness and look up: there’s still an impossibly long way to go. I look down: I’m level with the very top of the rainforest understorey, a mosaic of celery top pines and leatherwoods and tree ferns. In a moment, the forest floor will vanish beneath their interlocked crowns. In a moment, all I’ll have is tree and line and sky.
When botanists first climbed a hundred metres up into the California redwoods, they found what Preston calls “coral reefs in the air”: hanging gardens of ferns and mosses and lichens, ponds in old hollows swimming with plankton, beetles digging through rotting wood, and soil forming in forks that supported fruiting huckleberry bushes and bonsai trees, all feeding on moisture from fog.
The canopies of wet eucalypt forests are entirely different. They aren’t bathed in constant coastal fog, and they don’t provide a stable enough habitat for epiphytes because they shed their bark like snakeskin – dislodging parasites and evicting any moss, fungi or lichen that have moved in.
Instead, these islands aloft are dominated by animals and insects. As eucalypts reach middle-age they begin to form gnarled hollows, which become homes for possums and microbats, spiders and skinks, insects and a diversity of birds.
As I climb past a hollow decorated with the lacework curtains of spiderwebs, I feel a strange kinship with their maker, dangling from a fine thread in a tree many thousands of times my size.
Above the understorey, the world is made of light.
I climb through the fork of the first branch, where it cleaves in two and curves up like a living candelabra, just the first of many. After 25m of limblessness, my line runs in and around a woody maze that I work my way through, bumping against burls and batting away the whippy leaves of fresh shoots.
From below, perspective compressed the tree to a couple of layers. Up here, I’m clambering through endless storeys of branches – each the girth of the biggest tree in a suburban park – splitting and replicating and fanning out to catch stray rays of sunlight that filter past the dozens of limbs still above.
When I next stop to catch my breath, an intense hum drives me to distraction, vibrating directly into my skull.
Pearce has patiently been climbing at my pace, and I ask him, “What insects are we hearing?”
“They’re crickets.”
“It sounds like they’re in the trees.”
He laughs. “They’re probably all around us, mate. It’s a three-dimensional space.”
For most of my life I’ve been moving through the world in a rigid X-Y plane, and now I’ve flipped into another dimension – the Z-axis. But while I can only travel vertically, every other critter can move in the fullness of three dimensions.
“There’s 30 or 40 metres of forest below us, and there’s still 40 metres of forest above us,” Pearce says. “Different species and life forms occupy different zones in that space.”
From below, perspective compressed the tree to a couple of layers. Up here, I’m clambering through endless storeys of branches – each the girth of the biggest tree in a suburban park.
In springtime, he tells me, birdsong contours through 3D world.
“From the ground, everything’s above you. But when you’re in the middle, it’s like – the thornbills only operate down there, and the grey fantails work there and that’s their zone…and then there’s the eagles and the cockatoos at the very, very top.”
I’d thought climbing would give me the perspective to appreciate the size and significance of this tree. But just like on the ground, inside its convolutions it’s impossible to see the whole.
“The way we often think about organisms and environments – and this is despite our best intentions – is to think about an organism as something that develops externally to its environment,” says Dalia Nassar, an environmental philosopher at the University of Sydney.
And yet, everything on this planet has developed within intricately interconnected life support systems: the lithosphere, hydrosphere, biosphere, atmosphere.
“The organism is a part of the environment in such a way that it’s almost impossible to separate it. You can’t say where the organism ends and where environment begins.”
Plants, Nassar points out, demonstrate this far more radically than animals.
“Plants are rooted, they are of their environment, they are of the soil – they are transformed by the soil at the same time that they are transforming the soil,” she says. “They are determining the temperature, they are determining the rain season, just as much as they are determined by it.”
Much of our scientific understanding of tree-environment relationships has been revealed in recent decades, according to the University of Waikato’s Barbour, who works with Nassar to create a conversation between plant science and philosophy.
“There’s a whole lot of things we’ve learned about how plants respond very, very sensitively to their environment,” Barbour explains. “Because trees can’t move, they can’t move away…when things get rough. They have to be able to respond to environmental stresses.”
We’ve known about how they respond to light for a long time, she says. “But more subtle things like nutrient availability and water availability within the soil and how that varies over space and time, and how plants respond to those variabilities – that’s the kind of thing that we’re just learning about more now.”
Trees of the same species can grow differently according to how much light and water they receive, or how densely they’re planted, or the wind or soil conditions. Even in an individual tree, the leaves at the lighter end of the canopy are anatomically distinct from the leaves below.
“The tree senses its context from the beginning and develops in dialogue with it,” Barbour and Nassar write in an Aeon essay exploring their collaboration. “Trees are so adaptive to their surroundings that a human equivalent to tree plasticity would be certain people growing large webbed feet (like diving flippers) simply because they swim a lot.”
You know you might go out one day and then find the largest living thing in the Southern Hemisphere right around the corner,” says Tassie tall tree hunter Jan Corigliano. “It’s pretty tantalising.
In turn, trees engineer their world as they grow, both locally – creating microenvironments that affect light, nutrients and water, often determining which species grow around them – and globally, driving biogeochemical cycles.
There’s also evidence under some conditions for plants picking up on the chemical signals of others – say, the volatiles released by a tree attacked by insects – as well as emerging research that shows some species share resources through underground mycelial networks.
Trees aren’t static or passive beings: they’re active agents in their environment, both shaping the world and being shaped by it. In fact, Barbour and Nassar argue that trees are synecdoches – “a part that signifies or expresses a whole”.
“We have, for too long, seen natural beings as static objects that develop in separation of one another,” Nassar tells me. “We have failed to properly conceptualise the dynamic and collaborative nature of the world.”
In reality, we’re all dynamic processes, developing in collaboration – humans included.
“As living beings, we’re participating in these processes,” Nassar says. “We’re affecting them as much as they are affecting us. Like plants, we’re transforming the environment in vast ways, but we have to think about how this is transforming us.”
The crown of Lathamus Keep doesn’t peter out: it stretches expansively into a multi-tiered dome, big enough to hold dozens of people in its branches.
I stop climbing just before the end of my line, when I find Sanger lounging in a massive fork as if it’s a hammock. The other climbers – Sophie and Kevin and Ethan – are already here, and we join them, draping ourselves over branches or hanging suspended in space, the six of us, 70m aloft.
Peanut-butter-and-jelly muesli bars are passed around; we point out blossoms and talk about government logging quotas and tell stories of the day they measured this tree to be the biggest blue gum in the world, sending a climber up to its topmost branches, no thicker than my wrist.
As we chatter, I try to think of all the things I’m not seeing: the millions of processes and interactions invisible to the human eye. This organism is pulling water 80m up using an impressive vascular system. Every leaf in sight is using this water as it takes in carbon dioxide through its stomata and produces energy through photosynthesis. This magic of light into life continuously builds carbon into the skin of Lathamus Keep, into its roots and trunk and branches.
This forest, Sanger tells me, is incredibly carbon dense. With a team of citizen scientists, she recently surveyed two hectares of the Grove of Giants – climbing and measuring the eucalypts, the understorey and the soil. Preliminary results show this forest holds the highest amount of carbon of any forest in Tasmania.
“There’s about 1250 tonnes of carbon per hectare in these forests, which is an absolutely phenomenal amount,” she says. “Globally, that’s some of the highest carbon [density] you’ll ever find.”
In the process of building itself layer by layer, Lathamus Keep is also producing a gift of its own: oxygen. Just like us, every plant on this planet is constantly breathing in and out, creating and maintaining the composition of the thin blue skin of an atmosphere we all depend on.
“They’re the reason we’re here to begin with,” Sanger says.
I know this intellectually, but every time I see a tree, I don’t think: You’re the reason I’m alive. I get too caught up in my own bubble to think of all the intimate chloroplastic relations of our planetary one. But here in the forests of southern Tasmania, here with my whole weight supported by this living pillar of carbon and water and sunlight, I’m beginning to see how much our lives depend on it.
Let’s leave me dangling in the crown for a moment. Bear with me; we’re going higher.
In March 1965, Soviet cosmonaut Alexei Leonov became the first human to walk in space. He hurtled into orbit in the tiny Voskhod 2 spacecraft, crammed up against fellow cosmonaut Pavel Belyayev. As they drifted above Egypt, Leonov suited up, pulled himself into the void, and let go. A thin line was all that tethered him to life. For 12 minutes he spun gently as the Earth spun beneath him – bright and curved, with clouds and mountain ranges and oceans and continents speeding by.
“The Earth was small, light blue, and so touchingly alone,” Leonov later wrote. “Looking back at our blue globe from such a distance profoundly changed my vision of space and time.”
Many who have ventured into space since have recorded a similar feeling: a kind of orbital perspective, gained from seeing our world from the outside. Hanging in the star-filled void, a switch seems to flip in their brains and they can see the interconnectedness of our planet and its systems – see its vastness and its insignificance, its wondrousness and its fragility.
Edgar Mitchell, lunar module pilot on Apollo 14 and the sixth man to walk on the Moon, explained to People magazine in 1974: “You develop an instant global consciousness, a people orientation, an intense dissatisfaction with the state of the world, and a compulsion to do something about it. From out there on the Moon, international politics look so petty. You want to grab a politician by the scruff of the neck and drag him a quarter of a million miles out and say, ‘Look at that, you son of a bitch’.”
This phenomenon has been termed “the overview effect”.
It was profoundly difficult for the first astronauts to bring what they saw home. But Leonov was an artist.
Every time I see a tree, I don’t think: You’re the reason I’m alive. I get too caught up in my bubble to think of the intimate chloroplastic relations of our planetary one.
After the unexpectedly harrowing experience of returning through the tiny airlock – his spacesuit had inflated, forcing him to manually vent oxygen – an exhausted Leonov reached for his sketchpad.
Weightless, with coloured pencils attached to his wrist by string, Leonov sketched his impressions of the spacewalk. But he didn’t draw Voskhod 2, or himself floating in space, or even the endless vistas of stars. Instead, this first astral artwork depicts the fragile blue curve of our atmosphere pressing up against the void, with the sun alight in the threshold between.
“I tried to capture the different shades of charcoal rings that make up the Earth’s atmosphere, the sunrise or air glow over the Earth’s horizon, the blue belt covering the Earth’s crust, and the spectrum of colours I had observed looking down at the globe,” Leonov later said.
And when he returned home, this sketch came with him – bringing us our first vision of the Earth from above.
“The Earth was small, light blue, and so touchingly alone,” Leonov said after the flight. “Our home that must be defended like a holy relic.”
When Pearce suggests that we start heading down, I don’t want to go.
Up in the crown I have a sense of infinite space: from the shadowed understorey I’ve stepped up into a place of vast horizons, punctuated only by other giant trees, each its own island in a wrinkled sea of rainforest canopy.
It radiates out for 100 hectares, and beyond I see waves of hills that have been logged and uniformly replanted – severing the complex, long-tended relationships that intact forests cultivate with the earth and sky. This grove is within the logging coupe, and may be next.
On the 2D surface of the planet, we’re safe within our own perspectives of the world. But like launching into space, ascending into the canopy adds another dimension. Suspended here by a single tether, looking out and up, I’m confronted with how intimately and integrally we’re tied to this place; I can see what we’re losing by cutting our own lines.
I unclip my foot ascenders so I’m supported just by my harness. My climbing line drops off into the abyss behind me, falling some 70m to a ground I can’t yet see. The only thing holding me up is a single device gripping the line.
I pull the release lever, and begin the journey home.
Some 20 kilometres south of the Grove of Giants, within the Tasmanian Wilderness World Heritage Area, is another incredibly carbon dense forest.
“These tall eucalypt forests are world-renowned for the amount of carbon they can store,” says Tim Wardlaw, forestry scientist at the University of Tasmania and site manager of the Warra Supersite.
He would know, because he can measure it.
Warra is the southernmost node of the Terrestrial Ecosystem Research Network, and it’s equipped with an 80m instrument tower capable of mapping the flow of water, nutrients and energy through the forest of messmate stringybark (Eucalyptus obliqua).
The tower was only installed about a decade ago, but the world has changed a lot since then.
Evidence had previously shown that forests respond to a heatwave in one of two ways. If there isn’t much water, they shut their stomata to stop water loss, and thus take in and store less carbon, becoming less “productive”. If water is still available, then the stomata stay open and trees become more productive, as photosynthesis is efficient at high temperatures.
These two scenarios were “the status quo”, Wardlaw says: “All the models that are in existence in Australia assume that behaviour. And then Warra came along.”
November 2017 brought three weeks of hot weather. The soil and the atmosphere weren’t particularly dry, so the trees didn’t shut their stomata. But the tower’s measurements during the heatwave showed that photosynthesis virtually stopped.
We’ve become mythological beings, capable of modifying systems at a planetary scale … Trees are mythological beings too, capable of transforming the world in just as extraordinary ways.
“This is the first time it’s ever been seen,” Wardlaw says.
In fact, Warra became a net source of carbon, putting about a tonne of carbon per hectare back into the atmosphere – a massive number when extrapolated out across the 800,000ha of forest around the site.
“That’s the flipside of being a really productive forest,” he says. “It can flip from being a really strong carbon sink to a really strong carbon source.”
The exact mechanism is not yet understood, but Wardlaw says they need to find out fast. If forests stop absorbing and start emitting carbon as the climate heats up, this could initiate a strong positive feedback loop that both exacerbates warming and endangers these forests.
“The question then becomes, can the forest acclimate?” Wardlaw asks.
And what will happen to us if it doesn’t?
Down, down, down, into free space, abseiling back to the world of tarmac and currency and nation-states, the world we’re building at the expense of the living one.
Down, down, down, we’ve dug, to the bodies of long-dead trees and plants and organisms that were transformed into coal seams, oil deposits and gas reserves by the immense pressures of rock, heat and deep time. Millennia-long cycles submerged these dark rivers of carbon and energy. By forcing our way down into extinct worlds, we’ve cheated the system.
“Like exorcists,” writes Andri Snær Magnason in his 2020 book On Time and Water, “we disturbed their infinite sleep, pumping them back to the surface, rekindling fires and harnessing hundred-million-year-old sunshine as it lay dormant in the Earth’s belly.”
As we burn these fossil gods we release their ancient carbon. The world warms. Today’s forests, evolved to drink in carbon, struggle to absorb the excess. Some will switch to emitting it. The world will warm further, driving more intense and more frequent fires, heatwaves and droughts, pulling us deeper into the feedback loops that we’re fighting to untangle ourselves from.
“We live,” Magnason writes, “in mythological time.”
We’ve become mythological beings, capable of modifying physical and biogeochemical systems at a planetary scale. We’re busy breaking cycles even as we try to remember that we’re part of them – that we’ve been in a symbiotic relationship with this planet since long before tetrapods took their first breaths.
Trees are mythological beings too, capable of transforming the world in just as extraordinary ways. Research is now revealing how entirely they are transformed in return – they’re of the soil and yet create it; they make the atmosphere and yet it literally makes and breaks them.
Like us, they’re animated carbon, alight with the endless possibilities of the world. They’re inescapably bound to the planet, and so are we.
As I dip below the canopy, a bright breeze turns to shadowy stillness. In moments, my feet are once again on the spongy forest floor again beside Lathamus Keep. After the long, tiring, stop-start ascent, it took just minutes to drop 70m down.
I take stock: I’ve lost skin on my palm, scratched my arms, exhausted my shoulders – all gentle reminders of the gift of the climb, of existing alongside this living, life-giving being.
As everyone takes off their helmets and harnesses, we joke and chatter along with the birds. Lunch is the main topic of conversation. We’re all starving. We pack up the gear quickly because there’s still two kilometres to walk, through a forest that’s co-creating our atmosphere.
We head back on a 2D plane to the world we’ve made. As we walk, each breath is a reminder that part of us is being made and remade over and over again, high above in that open field of light.
