It seems that trees communicate and collaborate through an underground fungal network. What are they sharing?
In her childhood, Suzanne Simard often explored the old-growth forests of Canada with her siblings, building forts out of fallen branches, collecting mushrooms and huckleberries, and sometimes even tasting the soil (she liked the taste). Nearby, her grandfather and uncles were engaged in low-impact logging with horses, selectively harvesting cedar, Douglas fir, and white pine. Because the number of trees felled was minimal, Simard barely noticed any difference. The forest seemed endless and ancient, a shimmering expanse of conifers and rain-drenched jewels, teeming with ferns and fairy bells. To her, it was a realm of mythic perfection, an unspoiled natural world. When she began attending the University of British Columbia, she discovered forestry and was overjoyed to find a scientific field devoted to the domain she loved. It felt like a natural choice.
By the time she was in graduate school at Oregon State University, Simard understood that commercial clear-cutting had almost entirely replaced past sustainable logging practices. Loggers were transforming diverse forests into uniform plantations, systematically planting them on upturned soil after removing most of the underbrush. The prevailing thought was that newly planted trees would thrive without competitors. Yet, these trees often proved more susceptible to disease and environmental stress than their old-growth counterparts. Notably, Simard observed that when nearby aspens, paper birches, and cottonwoods were removed, up to 10% of the newly planted Douglas firs fell ill and died. The reason wasn’t obvious. The seedlings had ample space and received more light and water than the trees in denser, older forests. So why were they so vulnerable?
Simard suspected the answer lay hidden in the soil. Underground, trees and fungi form partnerships called mycorrhizae. The thread-like fungi encase and fuse with tree roots, helping extract water and nutrients such as phosphorus and nitrogen, while the trees provide the fungi with carbon-rich sugars produced through photosynthesis. Studies had suggested these mycorrhizal connections could link plants and be ecologically significant, but most scientists focused on greenhouse or laboratory settings, rarely venturing into the field. For her doctoral dissertation, Simard decided to investigate the fungal connections between Douglas firs and paper birches in the forests of British Columbia. She received little encouragement from her mostly male colleagues, except for her advisor. “The old foresters would tell me to study growth and yield,” Simard told me. “But I was interested in how these plants interacted. They thought it was all girly stuff.”
Now sixty and a professor of forest ecology at the University of British Columbia, Suzanne Simard has spent nearly three decades studying the web of roots and fungi in the Arctic, temperate, and coastal forests of North America. Her early intuition about the importance of mycorrhizal networks proved prophetic, eventually sparking a new field of research that overturned long-standing misconceptions about forest ecosystems. By analyzing the DNA at the tips of roots and tracing the movement of molecules through underground conduits, Simard discovered that fungal threads connect nearly all trees, even those of different species. Carbon, water, nutrients, alarm signals, and hormones travel from tree to tree through these subterranean circuits. Resources tend to flow from the oldest, largest trees to the youngest, smallest ones. A chemical alarm signal from one tree can prompt nearby trees to brace for danger. Saplings cut off from the forest’s underground lifeline are far more likely to die than those connected to the network. When a tree is on the brink of death, it may transfer a substantial amount of its carbon to a neighboring tree.
Initially, Simard’s colleagues were skeptical, even dismissive of her early work. Today, she is widely recognized as one of the most rigorous and innovative scientists studying plant communication and behavior. David Janos, a co-editor of the journal *Mycorrhiza*, describes her published research as “sophisticated, imaginative, and cutting-edge.” Jason Hoeksema, a biology professor at the University of Mississippi who also studies mycorrhizal networks, agrees: “I think she’s really advanced the field.” Some of Simard’s studies are now featured in textbooks and are widely taught in graduate-level forestry and ecology courses. She was also a major inspiration for Patricia Westerford, the visionary botanist in Richard Powers’s Pulitzer Prize-winning novel *The Overstory*. In May, Simard’s own book, *Finding the Mother Tree*, will be published by Knopf. It is a vivid and captivating memoir of her lifelong quest to prove that a forest is much more than just a collection of trees.
Since Darwin, biologists have emphasized the individual perspective, highlighting the ceaseless competition between distant species, the struggle of each organism within a population for survival and reproduction, and the underlying relentless ambition of selfish genes. Yet, occasionally, some scientists have advocated focusing on cooperation over self-interest, and on the newly emerging properties of biological systems rather than individual units.
Suzanne Simard stands in Nelson, British Columbia, a Douglas fir sapling cradled in her right hand. She’s studying how trees exchange carbon, water, and nutrients through an underground fungal network.
Before Simard and other ecologists uncovered the vastness and importance of mycorrhizal networks, foresters typically viewed trees as isolated individuals, each competing for space and resources, indifferent to one another. However, Simard and her colleagues demonstrated that this framework was overly simplistic. Ancient forests were not merely patient gatherings of organic beings tolerating one another, nor were they merciless battle royals. They were vast, old, and complex societies. Yes, there was conflict within these forests, but there was also negotiation, mutual aid, and perhaps even altruism. The trees, understory plants, fungi, and microorganisms were intimately connected, communicating and depending on one another, leading some scientists to describe them as superorganisms. Recent research shows that mycorrhizal networks permeate grasslands, meadows, chaparrals, and the Arctic tundra. These symbiotic partners link the Earth’s soil into nearly continuous living networks, their scale and complexity unfathomable.
“They taught us that a tree is a lone entity finding its own way,” Simard told me. “But a forest is not like that.”
In the summer of 2019, I traveled to the small mountain town of Nelson in southern British Columbia, where Simard grew up, to meet her. One morning, we ascended a winding road to an ancient stand of trees and began our hike. The first thing I noticed was the smell. The air was a faintly sweet, tangy scent, like orange peels and cloves. Overhead, broad green canopies filtered the sunlight, generously showering it on the forest floor in some places, scattering it in others. The roots of ancient trees burrowed beneath the path like sea serpents. I was so absorbed in my own experience of the forest that I hadn’t thought to consider how the forest might be experiencing us. That was until Simard mentioned it.
“I think these trees are very perceptive,” she said. “They’re keenly aware of what’s growing around them. I’m really interested in how they perceive us.” I asked her what she meant. Simard explained that trees can sense nearby plants and animals and alter their behavior accordingly. For instance, the gnawing of insects might trigger the production of chemical defenses. Some studies suggest that plant roots grow towards the sound of running water and that certain flowers can detect the buzz of a bee’s wings and sweeten their nectar in response. “Trees are aware of a lot of things,” Simard said. “So why not us?”
I thought about it. We’d been walking through this forest for over an hour. Our sweat glands emitted stimulating chemicals. Our voices and footsteps sent pressure waves through the air and soil. Our bodies brushed against and moved branches. Suddenly, the idea that the trees might be aware of our presence didn’t seem far-fetched at all.
Further along the trail, we found a small sunlit hollow where we stopped to rest and talk. We leaned our backpacks against a mossy, lichen-covered log. From the green blanket of the log sprouted countless tiny plants. I asked Simard what they were. She leaned closer, pushing stray strands of blond hair behind her ear, and began naming what she saw: Queen’s cup, a type of lily; five-leaf bramble, a wild raspberry; and saplings of cedar and hemlock.
As Simard examined the log, a section crumbled away, exposing its rotting interior. She dug her thumb into the wood, revealing a rubbery, mustard-colored fibrous network embedded in it.
“Fungi!” she exclaimed. “That’s Phellinus weirii, a very common mycorrhizal fungus,” she explained. She had encountered and studied this scenario countless times before.
“This mycorrhizal network is actually connected to that tree,” she indicated a towering hemlock at least a hundred feet tall. “That tree is supplying nutrients to these saplings.”
The trees, plants, fungi, and microorganisms within the forest are fundamentally connected. Their bond is so profound that some scientists describe them as a superorganism, with mycorrhizae in the soil providing the network.
In some of Simard’s earliest and most renowned experiments, she planted young Douglas fir and paper birch trees in forest plots, each tree enclosed in a separate plastic bag. In each plot, she injected radioactive carbon dioxide into the bag surrounding one tree and stable carbon isotopes (unusual carbon variations differing in neutron number) into the bag around the other tree. The trees absorbed these forms of carbon through their leaves. Later, she pulverized the trees and analyzed their chemical composition to see if there had been any underground carbon transfer between species. There was. In the summer, the flow of carbon was mainly from the smaller, typically shaded Douglas fir to the birch. In the fall, the evergreen Douglas fir was still growing while the deciduous birch was shedding its leaves, reversing the flow. As Simard had previously observed from the struggles of the Douglas fir, these two species seemed to depend on each other. No one had ever tracked such dynamic resource exchanges in the field through mycorrhizal networks. In 1997, part of Simard’s doctoral thesis was published in the prestigious scientific journal Nature. This was rare for forest researchers. Nature featured her study on the cover, titled “The Wood Wide Web,” a term that later appeared in many studies and popular science articles.
By 2002, Simard had secured her current professorship at the University of British Columbia, where she continued to study the interactions between trees, understory plants, and fungi. Collaborating with students and colleagues worldwide, she made a series of notable discoveries. Mycorrhizal networks were abundant in North American forests. Most trees were common species, forming symbiotic relationships with dozens to hundreds of fungi. In one study of six Douglas fir stands over about 10,000 square feet, nearly all the trees were intimately connected underground through the web. Larger, older trees were particularly well linked, associated with 47 other trees and predicted to connect to at least 250 more. Seedlings with full access to the mycorrhizal network had a 26 percent higher survival rate.
The question of whether plants possess some form of intelligence or agency has a long and intricate history.
Plants are clearly alive, yet they are rooted to the ground, silent, and rarely move on relatable time scales. They appear as passive aspects of the environment, often seen as elements within it rather than as entities in their own right. Particularly in Western culture, plants are frequently placed in a borderland between objects and living beings. This ambiguity has made the possibility of plant intelligence and sociality both fascinating and contentious.
In their 1973 book, *The Secret Life of Plants*, journalists Peter Tompkins and Christopher Bird claimed that plants had souls, emotions, musical preferences, felt pain, received thoughts from other beings, tracked planetary movements, and predicted earthquakes. They supported these claims by indiscriminately mixing genuine scientific discoveries with observations and supposed studies by eccentrics and mystics. Many scientists harshly criticized the book as nonsense. Nevertheless, it became a bestseller, making its way onto *The New York Times* list and earning satire in *The New Yorker* and *Doonesbury*. Since then, botanists have become particularly wary of claims about plant behavior and communication that veer too close to pseudoscience.
Simard, who considered becoming a writer before discovering forestry, often uses conservative language in her many published studies. However, she has also embraced metaphors and meditations when addressing the public, which has made some scientists uncomfortable. In her 2016 TED Talk, she spoke of an “infinite biological pathways world,” interdependent species “like yin and yang,” and “ancient trees passing wisdom to the next generation of seedlings.” She called the oldest, largest, and most connected trees in the forest “mother trees,” a term that evokes their nurturing abilities toward surrounding trees, even if they are not literal parents. In her writings, she compares mycorrhizal networks to the human brain and openly discusses her spiritual connection with forests.
Some scientists I interviewed are concerned that Simard’s research doesn’t fully support her most audacious claims. They also worry that popular writing related to her work sometimes misrepresents the true nature of plants and forests. For example, in his international bestseller *The Hidden Life of Trees*, forester Peter Wohlleben suggests that trees might optimally distribute nutrients and water, enjoy fusing their roots with fungi, and even exhibit “maternal instincts.”
“I think there is value in exciting the public about the remarkable mechanisms by which forest ecosystems function,” says Hoeksema. “But sometimes speculation goes too far. I find it really interesting to see how much experimental evidence will come out to support some of the big ideas we’re excited about.” At this point, other researchers have replicated most of Simard’s major findings. It is now widely accepted that trees and other plants are connected through mycorrhizal networks and that resources move among them. Most ecologists also agree that the amount of carbon exchanged between trees can benefit seedlings or severely stressed, shaded, or injured mature trees, though there is still debate over how significant this transferred carbon is for healthy mature trees. On a more fundamental level, it remains unclear why resources are exchanged between trees, especially when they are not closely related.
In their autobiographies, both Charles Darwin and Alfred Russel Wallace hailed Thomas Malthus as a key influence in independently shaping their ideas on natural selection in evolution. Malthus’s 1798 essay on population helped naturalists understand that all organisms are locked in a relentless competition for limited natural resources. Darwin, too, was influenced by Adam Smith, believing that competition among inherently selfish individuals in a free market led to social order and efficiency. Similarly, Darwin demonstrated that the dazzling diversity of species and their intricate relationships on Earth arose not from divine handiwork but from the inevitable processes of competition and selection. “Darwin’s theory of evolution by natural selection is clearly a projection of 19th-century capitalism,” wrote evolutionary biologist Richard Lewontin.
However, as Darwin well knew, ruthless competition wasn’t the only way organisms interacted. Ants and bees would die to protect their colonies, vampire bats regurgitated blood to prevent one another from starving, and velvet monkeys and prairie dogs risked their own safety to warn their kin of predators. There was a time when Darwin worried that such altruism might be “fatal” to his theory. As evolutionary biology and genetics matured, scientists converged on a resolution to this paradox: behaviors that seemed altruistic were often merely another expression of selfish genes, a phenomenon known as kin selection. Members of tightly-knit social groups usually share a significant portion of their DNA, so when one individual sacrifices itself for others, it is indirectly spreading its own genes.
But kin selection does not explain what looks like interspecies altruism among trees. This is akin to a practice more socialist than capitalist. Some scientists suggest that the generosity observed among trees might actually be the self-serving machinations of fungi. Descriptions of Simard’s research occasionally give the impression of trees being inert conduits for their own benefit, yet the thousands of fungi connecting them are organisms with their own motives and needs. If plants transfer carbon to root fungi, why wouldn’t those fungi use it for their purposes rather than simply passing it along to other plants? Perhaps they do. The fungi might be exercising some control. What appears as one tree feeding another might actually be fungi reallocating resources to promote themselves and favored partners.
“Where some scientists see large cooperative collectives, I see mutual exploitation,” says Toby Kiers, a professor of evolutionary biology. “They may both benefit, but they are always fighting to maximize individual payoffs.” Kiers is part of recent research suggesting that fungi symbiotic with plants engage in trade and export-import sanctions, sometimes exacerbating competition between plants through mycorrhizal networks.
The ecologists I interviewed agree that regardless of how or why resources and chemical signals move among the various members of symbiotic forest networks, the outcomes remain the same. What one tree produces can nourish, alert, or rejuvenate another. Such reciprocity doesn’t necessitate universal harmony but challenges the doctrine of individualism and softens the view of competition as evolution’s prime engine.
One of the most fundamental interpretations of Simard’s findings is that “forests behave as though they are a single organism,” as she put it in her TED talk. Some researchers propose that cooperation within and among species evolves when it helps one group outcompete another—altruistic forest communities may outlast selfish ones. This theory, though, remains unpopular among biologists who view natural selection beyond the individual as evolutionarily unstable and exceedingly rare. Recently, however, inspired by microbiome research, some scientists argue for rethinking the traditional concept of the individual, suggesting that multicellular organisms and their symbiotic microbes should be seen as units of natural selection. Even if the same microbial partners are not passed vertically from generation to generation, functional relationships between plant or animal species and their microbial communities persist—much like the mycorrhizal networks of ancient forests. Humans aren’t the only species inheriting the infrastructure of past communities.
The new understanding of trees as social beings carries urgent implications for forest management.
For thousands of years, humanity has relied on forests for food, medicine, and building materials. Likewise, forests have provided sustenance and shelter for countless species. But forests are vital for a deeper reason: they function as crucial organs of our planet. Between 425 and 600 million years ago, the colonization of land by plants and the subsequent spread of forests helped create the oxygen-rich, breathable atmosphere we enjoy today. Forests fill the air with water vapor, fungal spores, and cloud-seeding chemicals, reflect sunlight to cool the Earth, and supply essential rainfall to potentially arid inland regions. Researchers estimate that forests store approximately 400 to 1,200 gigatons of carbon in total, possibly exceeding the carbon pool in the atmosphere.
Significantly, much of this carbon is held in forest soils, sequestered by networks of symbiotic roots, fungi, and microorganisms. The world’s forests capture over 24% of global carbon emissions each year, but deforestation—destroying trees that would otherwise continue to store carbon—can drastically reduce this effect. When mature forests burn or are cut down, the Earth loses a precious ecosystem and one of its most effective climate-regulating systems. Logging ancient forests isn’t just the destruction of majestic individual trees but the unraveling of interspecies contracts of mutualism and compromise essential for the planet’s survival.
On a clear morning, Simard and I climbed into her truck and ascended a mountain towards a denuded area repeatedly logged. Vast expanses of barren land surrounded us, dotted with tree stumps, saplings, and woody debris. I asked Simard how old the trees that once stood here had lived. “We can actually calculate that,” she said, crouching beside a cleanly cut Douglas fir stump. She began counting the growth rings, explaining how their thickness reflected changing environmental conditions. Minutes later, she reached the outermost ring. “102, 103, 104!” She added a few years to account for early growth. This particular Douglas fir likely sprouted around 1912, the same year the Titanic sank, Oreos debuted, and the mayor of Tokyo gifted 3,020 cherry trees to Washington, D.C.
Mushrooms and toadstools are the fruiting bodies of fungi. Below ground, a network of filaments forms the roots.
Looking across the valley at the mountains beyond, the evidence of a century of logging was clear. Dirt roads snaked up and down the slopes. Some parts of the hillsides were densely covered with conifers, while other sections were treeless grasslands, sparse shrublands, and bare ground littered with sun-bleached trunks and branches. The overall landscape, haphazardly harvested, resembled the fur of a mangy dog.
By the time Europeans arrived on America’s shores in the 1600s, the forests of the future United States spanned about one billion acres, covering nearly half of the land. Between 1850 and 1900, American lumber production surged from five billion board feet to over thirty-five billion board feet. By 1907, more than 260 million acres of the original forests, about a third, had been lost. Similarly, throughout the 19th century, Canada’s forests were ravaged by over-exploitation. As cities grew and people moved away from rural and agricultural areas, timber companies were compelled to reforest logged areas, allowing trees to reclaim their former habitats. By 2012, America had over 760 million acres of forest. However, the age, health, and composition of these forests had dramatically changed. For instance, the Northeast now has 80% forest cover, but only about 1% of its old-growth forests remain.
Clear-cutting—the practice of cutting down all the trees in a specific area at once—is less common than it once was, but it still accounts for about 40% of logged acres in the U.S. and roughly 80% in Canada. In healthy forests, lush undergrowth captures significant amounts of rainwater, and dense root networks enrich and stabilize the soil. Clear-cutting removes these living sponges, disrupts the forest floor, depletes soil nutrients, and increases the potential for stored carbon to be released into the atmosphere. Sediment runoff into nearby rivers and streams can kill fish and other aquatic life, contaminating drinking water sources. Rapid deforestation harms and displaces countless birds, mammals, reptiles, and insects.
Simard’s research points to a more fundamental reason against stripping all trees from logging sites. The day after witnessing a clear-cut, we took a cable ferry across Kootenay Lake and entered the Harrop-Procter Community Forest. This mountainous area, covering nearly 28,000 acres, is home to clusters of Douglas fir, larch, cedar, and hemlock. In the early 1900s, much of the forest near the lake was burned for settlements, roads, and mining. Today, the land is managed by a local cooperative practicing ecology-based forestry.
The road up the mountain was rough, dusty, and littered with obstacles. Simard maneuvered the truck out of ruts and over large branches that jostled us in our seats. “Hold on tight!” she called. Eventually, she parked the truck by a steep slope, jumped out of the driver’s seat, and began to swiftly traverse the ground strewn with endless pine needles, stumps, and shattered trunks. Simard moved with a speed and agility that made it hard for me to keep up, but I managed to follow her across most of the debris until we reached a clearing. The ground here was mostly bare and brown, but there were ancient Douglas fir trunks soaring 150 feet into the air, spreading their green canopies. The trunks of the remaining trees were marked with blue paint. Simard explained that she had asked Eric Leslie, the Harrop-Procter forest manager, to mark the oldest, largest, and healthiest trees to protect them from logging in this area.
When a seed germinates in an old-growth forest, it immediately taps into an extensive underground community of interspecies partnerships. Uniformly planted saplings after a clear-cut lack the old roots and their symbiotic fungi. These alternative forests, though adjacent, are isolated from one another and are much more vulnerable to disease and death. Simard believes that retaining some of the most robust and diverse mycorrhizal networks, through mother trees, significantly improves the health and survival of future saplings. She has been collaborating for years with scientists, North American timber companies, and some indigenous communities on this idea, referring to it as the “Mother Tree Project.” The project spans 27 stands across nine different climatic regions in British Columbia, comparing traditional clear-cutting with areas that retain varying proportions of old trees: 60%, 30%, or as little as 10%—about eight trees per acre. As I turned my attention to the mountains across Kootenay Lake, I saw several more experimental plots. These areas, though sparsely vegetated, were logged with precision, as if giants had carefully plucked specific trees one by one.
Since at least the late 19th century, North American forest managers have devised and tested dozens of alternative methods to standard clear-cutting. Examples include strip cutting (removing narrow bands of trees), shelterwood cutting (a multi-stage process where the upper canopy is mostly harvested after desired saplings have grown), and the seed tree method (leaving some mature trees as future seed sources). These approaches are used across Canada and the U.S. for various ecological reasons, often to benefit wildlife, but mycorrhizal networks are rarely, if ever, part of the rationale.
Sm’hayetsk Teresa Ryan, a Tsimshian forest ecologist who completed her master’s with Simard, explained that research on mycorrhizal networks and forest management practices based on them reflect indigenous wisdom and traditions often ignored or underestimated by European settlers. “Everything is connected, absolutely everything,” she said. “Many indigenous peoples talk about all species in the forest being interconnected, and many speak of the networks underground.”
Dusky fork moss.
Powderhorn lichen near Kokanee Glacier Provincial Park in British Columbia.
Ryan spoke of the Menominee forest in northeastern Wisconsin, a 230,000-acre woodland sustainably harvested for over 150 years. For the Menominee tribe, sustainability means “thinking about the entire system, its interrelationships, consequences, and feedback loops.” They maintain large, old, diverse trees, prioritize the removal of weaker and lower-quality ones, and allow trees to grow for over 200 years. This creates what Simard might call “grandmothers.” Though guided by ecology rather than economics, the management of the Menominee forest is highly profitable. Since 1854, more than 2.3 billion board feet have been harvested—about twice the volume of the entire forest—yet there are more standing trees today than when harvesting began. “To many, our forest might appear pristine and untouched,” the Menominee tribe states in a report. “In reality, it is one of the most intensively managed forests in the Lake States.”
On a mid-June afternoon, Simard and I headed to a bowl-shaped valley at the base of the Selkirk Mountains, 20 minutes from Nelson. In winter, it’s an active ski resort. We met her students and their friends there, equipped with shovels, water bottles, and bear spray, and began ascending the shrub-covered slopes. The aim was to identify the mycorrhizae of the endangered whitebark pine, which provides food and habitat for many creatures, including woodpeckers, Clark’s nutcrackers, and Douglas squirrels.
About an hour into the hike, we found such a tree—small, with bright leaves and a gray trunk. Simard and her assistants began exposing its roots with shovels and knives. The work was slow, tiring, and messy, with mosquitoes and flies constantly swarming around our hands and necks. I peered over their shoulders, struggling to see anything for a long time. But as they progressed, the roots became darker, finer, and more brittle. Suddenly, Simard discovered a tiny web-like network of white threads buried in the soil.
“Ah!” she exclaimed, beaming widely. “This is gold! Wow, incredible!” It was the first time I’d seen her so excited on our journey. “Sorry for the language,” she whispered. “Professors shouldn’t use such words.”
“Is that mycorrhizae?” I asked.
“It’s a mycorrhizal network!” she replied, grinning with delight. “Isn’t it amazing? We’ve definitely hit the jackpot here.”
She handed me a slender strip of root, about the length of a pencil, with numerous root hairs still covered in soil. The root hairs branched into even finer filaments. As I examined the delicate details, I noticed the tips of the thinnest fibers seemed coated in a waxy substance. Simard explained that the tiny white nodules, like bits of gum, were mycorrhizal fungi that had formed colonies on the pine roots, creating an intricate web of intertwined cables in the soil. These provided pathways for trade and communication, linking individual trees into a vast, interconnected network. This was the very essence of the forest, the foundation of one of the most populous and complex societies on Earth.
Trees have always been symbols of connection. In Mesoamerican mythology, a giant tree grows at the center of the cosmos, its roots reaching into the underworld, its trunk and branches encompassing the earth and sky. Norse cosmology features a similar tree, Yggdrasil. In popular Japanese Noh plays, there are stories of married pines eternally linked despite their distance. Before Darwin, naturalists used tree-like diagrams to represent the lineages of different species. Yet, for most of recorded history, living trees held astonishing secrets. Their celebrated connectivity was more than a metaphor—it was a material reality. Kneeling beneath that whitebark pine, gazing at its root tips, I realized I had never truly understood what a tree was. At best, I had recognized only half of a self-contained organism, unaware that it was a remarkable amalgamation of multiple beings.
We too are composite organisms.
Our bodies host diverse communities of microbes that regulate our immune systems and aid in digesting specific foods. Mitochondria, the energy-producing organelles within our cells, were once free-swimming bacteria, incorporated during the early evolution of multicellular organisms. Through a process known as horizontal gene transfer, fungi, plants, animals (including humans) continue to exchange DNA with bacteria and viruses. From skin, fur, or bark to genomes, any multicellular organism is a synthesis of other beings. Where life forms, they meet, mix, and meld.
Five hundred million years ago, as plants and fungi began their move from sea to land, they faced vast expanses of bare rock and impoverished soil. Plants could convert sunlight into sugars, but struggled to extract mineral nutrition from the Earth. Fungi were in a similar predicament. Had they existed separately, their early colonization attempts might have faltered. Instead, these two exiles—members of entirely different kingdoms of life—forged an intimate partnership. Together, they spread across continents, turned rock into fertile soil, and filled the atmosphere with oxygen.
Over time, different kinds of plants and fungi evolved even more specialized symbiotic relationships. Forests expanded and diversified both above and below ground. What one tree produced was no longer limited to itself and its symbiotic partners. Through embedded networks of roots and fungi, water, nutrients, and information began to move across forests in more distant and complex patterns than ever before. Across generations, the compound effects of symbiosis and co-evolution led forests to develop into intricate cycles. Once small, unknown exiles of the sea, trees and fungi together became a collective organism with unprecedented power and generosity.
After hours of digging roots and collecting samples, we began our descent into the valley. In the distance, peaks of granite in the Selkirk Mountains were covered in clusters of pine and fir. A breeze carried the scent of pine. To the right, a secretive squirrel buried something in the soil and dashed away. Like seeds waiting for the right conditions, a passage from “The Overstory” suddenly surfaced in my mind: “It’s no longer about individual trees or even separate species, but about the whole forest as a single living organism.”
