In 2018, the ecologist and writer Suzanne Simard was conducting research in the forested Caribou Mountains of western Canada when a thunderstorm rolled in. She was with her two teenage daughters and her close friend and colleague, Jean Roach. They saw flashes of lightning, heard a loud rumble and then they smelled smoke. They were forced to run the half kilometre back to Simard’s truck as the trees behind them caught alight and the air grew thick. As they ran, animals burst out of the forest: a deer, a rabbit, a grey wolf. They reached the truck with no time to spare, all four of them covered in soot and dirt. Overhead, helicopters began circling the orange-black air, dropping water on the flames below.

Wildfires have become an ever bigger problem in Canada. The 2018 wildfires were the biggest in British Columbia’s history, but this record was broken in 2021, and then again in 2023, when fires consumed an area three times the size of the Canadian province of Nova Scotia and the smoke travelled as far as New York City. The cause is not only global heating, which has brought hotter, dryer summers, but also the changing makeup of the forest. When logging companies clear forest, they replant it with fast-growing conifer species, but these trees are much more flammable than Canada’s diverse, native forest.

The country’s forests are so huge that for decades policymakers assumed that human activity would make little impact. “The rationale was that it will all come out in the wash: the trees will recover, the forests will grow back, and we’ll all be fine,” Simard says, speaking on a video call from Vancouver. But deforested areas do not fully recover, and thanks to logging, the wildfires and a devastating pine beetle outbreak, Canada’s forests, once a vast carbon sink, have since 2001 been a net emitter of carbon.

For four decades, Simard, a professor of forest ecology at the University of British Columbia in Vancouver, has been trying to convince foresters and policymakers that it doesn’t have to be this way. “What we’re doing by taking down forests is we’re undercutting our ability to solve, and to provide natural solutions to, climate change,” she says. Billions of dollars are being invested in carbon capture and storage technology, “but we actually have highly evolved organisms like trees and plants and algae that do this very thing much more effectively than anything we can possibly create ourselves. And yet, we’re cutting these creatures down.”

Her use of “creatures” is not a slip. Simard’s research, outlined in her bestselling 2021 book, Finding the Mother Tree, has suggested that trees are perceptive, collaborative, able to communicate with one another and to recognise kin. While scientists have traditionally viewed forests as a collection of individual trees competing for resources, Simard argues that they are better thought of as complex, interdependent communities, connected by an underground network of fungi known as mycorrhiza, through which nutrients are exchanged.

She names the oldest, biggest, most connected trees the “mother trees” (although trees are both male and female), to reflect their role in nurturing the surrounding forest. “I came up with the idea with a group of my students and colleagues in a bar, actually,” she says. “Everyone has a mother. Everybody knows they were nurtured and cared for and that they needed a boost up.” It turned out to be a better metaphor than she imagined, she says, because many cultures already speak of mother trees.

Simard is 65, with bobbed, grey-blond hair and a thick Canadian accent, all soft vowels and generous, round “r”s. She is friendly but seems guarded on our call, and she keeps her video background blurred. One senses she’d be much more comfortable trampling through the forest, sharing a beer on the bed of a pickup truck or, frankly, even hiding up a tree from a territorial mama grizzly – something she has actually had to do, bears being a common field hazard.

She describes herself as a “person of the forest”, having grown up in the Monashee Mountains of British Columbia, where her grandfathers and uncles worked as loggers, and where you can find a creek and a mountain named after her family. Simard followed her relatives into the industry by studying forest management at the University of British Columbia and taking seasonal work at a logging company in the early 1980s, when she was the only woman on staff. Later, she completed a master’s and a PhD in forest ecology at Oregon State University while working for the Canadian forest service as a research scientist.

Then, as now, logging companies clear-cut swathes of forest and replanted them with a fast-growing, single species of tree. They used herbicides to kill other plants that intruded on replanted forest, so that the conifers would not be outcompeted. Simard noticed, however, that replanted forests were often sickly. She observed that, contrary to received wisdom, seedlings seemed to fare better when they grew alongside other plants, and she came to suspect that the mycorrhiza that colonised the soil in diverse forests played a role.

Simard recorded that up to 10% of newly planted Douglas firs would get sick and die whenever nearby aspen or paper birch were removed. As part of her doctorate thesis, she demonstrated that fir and birch trees, which often grow together in the wild, trade nutrients. When a birch tree shades a fir, it transfers more carbon to it, via mycorrhiza. When the birch tree loses its leaves in autumn, the flow of carbon is reversed. In 1997, Simard published a landmark paper in the scientific journal Nature, outlining her findings. Nature ran it as a cover story, under the catchy title “The wood wide web”, referencing the underground network of mycorrhiza that enables trees to exchange nutrients. To be published in such a prestigious journal was a remarkable achievement for a forest service scientist, and the paper garnered international media attention because it suggested a new way of understanding how forests work, and what trees are: intelligent, perceptive beings. In 2002, she left the forest service for full-time academia.

While foresters have traditionally adopted the “masculine” lens of dominance and competition, Simard says her research helped introduce the missing “feminine perspective”. “The forest has got all of these connections and relationships, which women understand really well, and we nurture and honour these things. Men are sometimes, you know, blind to that.” She says that while the scientific community has often had a “harder time” absorbing her ideas, her work aligns with indigenous wisdom on how forests work and tends to make intuitive sense to lay people, too. People often write to her to tell her how her work resonates with them because, “they understood from their hearts that of course forests are social places … so it’s their intuition, their deep wisdom,” she says.

In 2016, Simard gave a TED Talk, “How trees talk to each other”, that has been viewed more than 8m times online. Her research turned her into a cult figure, inspiring a character in Richard Powers’s Pulitzer prize-winning 2018 novel, The Overstory, and paving the way for other popular science books such as Peter Wohlleben’s The Hidden Life of Trees and Merlin Sheldrake’s Entangled Life.

But, after the publication of The Mother Tree, Simard’s work was met with forceful scientific backlash. This was not limited to critiques in academic journals. One critic wrote a letter to her university accusing her of lacking scientific integrity, and emailed newspapers and magazines asking them to remove profiles of her. This seems to go beyond the realm of scientists debating the research, I say. “Yes, I agree,” Simard says. “I don’t know how unusual that kind of backlash is. I think it happens, and it’s kind of unfortunate. But I look back, and I think history repeats itself.” She cites the resistance faced by the primatologist Jane Goodall, because she named the chimps she studied, and James Lovelock, who first proposed the Gaia hypothesis, the idea that the Earth is a self-regulating system. Backlashes happen, she says, “when you have an idea that is a little revolutionary, that is not following the mainstream, that threatens the structure of the scientific method”.

Simard’s initial reaction was to retreat. She started keeping her camera off in Zoom calls. “It was really hard, that whole period,” she says. “Because my training is in science. My degrees are in science. My job is about science … It’s so hurtful because it’s your peers – it’s a rejection.” The forest ecology community is small, and some of those publicly criticising her work were former collaborators and co-authors. Did it seem personal? “I don’t know the answer to that question. You could ask them, but I hadn’t been in contact with them for a while, so I don’t know,” she says.

There are specific points of contention, over questions such as whether fungi are the prime way that nutrients pass between plants, or whether Simard underplays the role of competition in forests, and she sends me a paper in which she responds to these points. An overarching theme, however, is that there still isn’t enough evidence for Simard’s assertions. “That’s such a common refrain in science, and who can argue with that?”

Simard says she sometimes feels straitjacketed by science, which moves too slowly to meet the urgency of the climate crisis. “The scientific methodology has a lot of rules and sometimes it can feel suffocating,” she says, with a dry laugh. “When it dampens your curiosity, when it requires you to be less artistic than you might otherwise be. I could see the limitations of science. In this period of rapid climate change we need to be innovative, we need to be creative, we need to have all hands on deck and sometimes we need to break out of the scientific mould … I wanted to get out and try things and not be so worried. If I need 50 years of research to figure out how to restore this forest so that it’s got good structural diversity, I may not get there in time.”

Simard is also critical of science’s tendency to break down questions into their smallest parts, to focus narrowly on cause and effect, which she says makes it harder to study relationships and systems. “If I take forestry, for example, for a long time we studied: how do we grow bigger trees? And we got so focused on growing bigger trees that we didn’t think about the water and the plants and the animals and the impacts on them,” she says. “So we made a mistake by losing the whole picture. We were smart but not wise.” She takes inspiration from Indigenous wisdom, which has long recognised the interconnectedness of the forest and honed regenerative forestry practices over centuries of close observation of nature.

Since 2015, Simard has been running the Mother Tree Project, a huge national study that argues that scientists have massively underestimated the environmental harm of clear-cutting and explores more sustainable ways to log: for example, when foresters leave behind some of the biggest trees in the forest – the mother trees – and do not fully clear the land, they enable the forest to regenerate more effectively.

In her latest book, When the Forest Breathes, as in her first, Simard blends science and memoir, a stylistic choice that reflects how closely her personal life and the forest entwine. She writes not only about the Mother Tree Project, but about recovering from breast cancer – having been diagnosed in 2012 – and watching her daughters grow up and leave home. “There is no way to understand how something grows without also understanding how it dies,” she observes at the beginning of the book, and she writes of her grief at losing a young colleague, the researcher Amanda Asay, who died in a skiing accident in 2022, and her mother who, a few months later, sought medical assistance to die, after suffering from dementia and other health problems. “Although it was extremely difficult, I respected that my mum wanted to have a say, agency in her whole cycle of life,” she says. She is proud that Canada has taken a “progressive” stance by legalising assisted dying.

Simard feels buoyed up by the public pressure on the Canadian government to improve forestry practices, but she believes that while it wants to “do the right thing”, the geopolitical tensions between the US and Canada are pulling the government in the opposite direction. “One of the consequences of moving away from the US towards greater self-reliance is increasing resource extraction,” she notes.

While south of the border, the Trump administration is rolling back environmental protections and promoting climate change denialism, Simard believes Canadians’ lives have already been so dramatically affected by the changing weather that they are more likely to believe the science. “Climate change is all around us. People are literally trying to protect their lives and property from wildfire, it’s been building over the past decade or so. And so, it’s real, right? We can feel it in our everyday lives.” Instead, she believes the bigger challenge in Canada is combating a feeling of defeatism. “I hope when people read this book, they come to feel agency in motivating change.”

She wonders if this new book will provoke a renewed backlash but says she feels better equipped to cope if it does. “Then, I was so taken aback, I was so surprised,” she says. She hopes this time she won’t be quite as hurt. It helps, she says, to remember that her work has not been “universally rejected”, and that many people find it helpful and illuminating.

In June, after she finishes her book tour, Simard plans to take a sabbatical from teaching to spend more time in the woods and mountains that surround her home town of Nelson, British Columbia. One gets the impression, when she describes her upcoming travel schedule, that returning to her home turf will be a relief. She lives alone now that her daughters are at university, in Vancouver and Corvallis, Oregon. Her partner, Mary, also lives in Oregon. “We’re all within an eight-hour drive – in Canadian terms, eight hours is not that much,” she says.

It has been unusually warm in the western US this year. “In my little town, where we usually get feet of snow through winter, we’ve had almost none. It’s very worrisome,” she says. Like many of her neighbours, she’s already thinking about the next wildfire.

In the book-length essay Death By Landscape, Elvia Wilk gives a potted history of fiction in which humans turn into plants. There is Daphne, in Ovid’s Metamorphoses, who is so afraid she will be raped by Apollo that she begs her father to transform her into a laurel tree. More recently, in Han Kang’s The Vegetarian, brutalised Yeong-hye refuses food and takes root. Wilk argues that, in these stories and others, “a woman implants herself in despair, but also protest”.

Rhett Davis’s Arborescence – an even-tempered, quietly satirical speculative novel – tells a story of cross-species transformation at scale. The narrator is a man, Bren, who at the outset is dismissive of unverified reports of “people standing around believing they’re trees”. His partner, Caelyn, is curious and undaunted. She drags him out for a hike. “I’m not sure I like forests,” he complains. “I don’t like that part of The Lord of the Rings at all. It’s really terrifying.”

At “The Queue” where he works, Bren processes “work packages” for a manager he suspects is a “disembodied intelligence” that has hired a physically attractive human to represent him in meetings. Caelyn, by contrast, is “good at being good at things”. She trades a garden centre job for PhD research into people turning into trees. She becomes a famous academic, flying around the world arguing that humanity should let people “arboresce”, if that is what they choose to do.

As the world descends into reforestation, Bren dallies and drifts. For a while, he is Caelyn’s assistant. He thinks about a rabbit he didn’t rescue from the road. He reflects that work for The Queue “meant nothing”. He is easily distracted by food and drink. He eats a Reuben sandwich, even though it has fallen apart. He drinks gin with his mum. He visits his father in a nursing home, and listens (soberly) to “a confused monologue of goals, mud, elbows to the face, roaring crowds and a team that doesn’t exist”.

Bren’s father’s death and references to rising temperatures give a clue to the real-world contexts that ground the novel. Mass voluntary arborescence is a provocative solution to the twin challenges of ecological sustainability and caring for an ageing population, pitched in the tradition of Jonathan Swift’s 1729 A Modest Proposal. The Irish writer’s viciously extended joke proposes a rational response to the problem of famine in Ireland: the Irish poor should sell their children as food for the wealthy.

The only snag with aborescence is that people are attached, quite deeply, to other people. Bren visits a tree that was once his best friend from school and feels angry. They bonded over a comic and TV programme called Voidstar. Descriptions of Voidstar episodes punctuate the novel; their ambient weirdness and nostalgia contrasts sharply with Caelyn’s practicality and empiricism. Voidstar is a shapeshifting character, appearing variously as a “small faceless child”, “a seedling in a sleek, futuristic city”, and in one episode as the “gentlest chaos”.

This description fits the novel itself. It is written in brief sections, some as short as a single line (“There are too many ways we can pretend we’re not here”). The writing is quick and careful, punchline-adjacent and mildly disorienting. The world outside a near-future Australia is sketchy, filled in with references to the UN and experts who say things like “this is the biggest economic change to affect the world this century”. Arborescence cycles through the familiar moods of the west’s environmental soul-searching – cynicism and optimism, dynamism and depletion, nostalgia and grief – but is an econovel that feels insulated from real ecological crisis.

Caelyn’s research doesn’t establish a definitive reason why so many people are driven to go through the painful process of rooting to the soil. I wanted to understand why Bren himself feels increasing despair and desire for escape. One of the few clues comes when he reflects on his gender. “As a heterosexual male partner of a heterosexual woman in the first half of the twenty-first century, I should be able to support her dream and forgo dreams of my own,” he ruminates, “but something about that remains hard to swallow.”

When was the last time you stopped to say thank you to a tree? Perhaps it’s something we should do more often. After all, we owe them everything, from the air we breathe to the soil beneath our feet, and far less obvious things too. We have trees to thank for the swirl of our fingerprints, our posture, and possibly even our dreams.

In her new book, British tree science consultant Harriet Rix presents trees as an awesome force of nature, a force that has, over time, “woven the world into a place of great beauty and extraordinary variety”. How have trees done this? And can they really be said to possess “genius”?

If you think of life first emerging from the sea, hundreds of millions of years ago, you might picture something like the Tiktaalik, a human-sized floppy-footed fish that hauled itself out of the shallows some time in the Late Devonian. But the evolutionary eureka moment arguably came long before that, when one lucky green alga washed up on the Cambrian shore and managed to survive the deadly UV light on land.

“Plants learning to survive and use UV light was a thunderbolt,” writes Rix. It “allowed a whole new chemistry to emerge, root and branch, in a whole new place: dry land … Safe from predators, who for the moment were left in the sea behind them, these photosynthesising cells started on a path that led to the amazing complexity of trees.”

Viewed on cosmic fast forward, as part of “a strange, apparently accelerated world, in which continents drift around like rubber ducks, bumping into one another”, trees seem almost godlike, using their biochemical wizardry to transform the Earth from a stony, storm-ravaged wasteland into a place where life could thrive. They broke barren rock into soil, canalised flood waters into rivers, pumped oxygen into the atmosphere, and turned the desert green.

Element by element, trees have learned to control water, air, fire and the ground beneath us, as well as fungi, plants, animals, and even people, shaping them according to their own “tree-ish” agenda. Some fairly knotty chunks of biochemistry and evolutionary history are smoothed by lush descriptions of contemporary habitats as Rix travels the world, from the cloud forests of La Gomera to the junipers of Balochistan. She is an intrepid and erudite guide.

Despite the title, this is not a book that gives much weight to questions of tree consciousness or intelligence. It doesn’t stop to consider whether our leafy friends have feelings. Rix acknowledges that the early work of Suzanne Simard – whose research into resource exchange between trees via underground mycelial networks gave rise to the concept of the wood wide web – was “beautiful field science” and “immensely compelling”, but she gives short shrift to subsequent anthropomorphic claims that trees “talk” or “love” or “mother” one another. “Putting a nurturing mammalian face on to the giants of the forest was also a massive betrayal of the complexities of an organism that could be thousands of years old,” she writes. “Thinking of the 5,000 years in which Methuselah [a storied bristlecone pine] has had to negotiate existence makes simple narratives about the gentle exchange of nourishing sugars seem astoundingly trite.”

What, then, is the genius of trees? Rix locates it in the elegant solutions they have devised to the constantly changing riddle of life. It’s a genius you can smell in the rich terpenes given off by trees to seed clouds, generating rain and expanding their own habitats. It’s a genius you can taste in the sweet fruit that makes animals do trees’ bidding, and arguably gave our simian ancestors their brains. It’s a vast, generative genius that has nurtured our own. Our clever fingers – and fingerprints – evolved to grip their branches. Our dreams were born in the safe, fragrant nests we built in their canopies. This is why, Rix argues, we find the smell of wood so comforting, and why we like to press our noses between the pages of books. Genius is too small a word for all of this.