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The Secret Life of Trees: The Astonishing Science of What Trees Feel and How They Communicate

“A tree can be only as strong as the forest that surrounds it.”

The Secret Life of Trees: The Astonishing Science of What Trees Feel and How They Communicate

Trees dominate the world’s the oldest living organisms. Since the dawn of our species, they have been our silent companions, permeating our most enduring tales and never ceasing to inspire fantastical cosmogonies. Hermann Hesse called them “the most penetrating of preachers.” A forgotten seventeenth-century English gardener wrote of how they “speak to the mind, and tell us many things, and teach us many good lessons.”

But trees might be among our lushest metaphors and sensemaking frameworks for knowledge precisely because the richness of what they say is more than metaphorical — they speak a sophisticated silent language, communicating complex information via smell, taste, and electrical impulses. This fascinating secret world of signals is what German forester Peter Wohlleben explores in The Hidden Life of Trees: What They Feel, How They Communicate (public library).

Wohlleben chronicles what his own experience of managing a forest in the Eifel mountains in Germany has taught him about the astonishing language of trees and how trailblazing arboreal research from scientists around the world reveals “the role forests play in making our world the kind of place where we want to live.” As we’re only just beginning to understand nonhuman consciousnesses, what emerges from Wohlleben’s revelatory reframing of our oldest companions is an invitation to see anew what we have spent eons taking for granted and, in this act of seeing, to care more deeply about these remarkable beings that make life on this planet we call home not only infinitely more pleasurable, but possible at all.

Illustration by Arthur Rackham for a rare 1917 edition of the Brothers Grimm fairy tales. (Available as a print.)

But Wohlleben’s own career began at the opposite end of the caring spectrum. As a forester tasked with optimizing the forest’s output for the lumber industry, he self-admittedly “knew about as much about the hidden life of trees as a butcher knows about the emotional life of animals.” He experienced the consequence of what happens whenever we turn something alive, be it a creature or a work of art, into a commodity — the commercial focus of his job warped how he looked at trees.

Then, about twenty years ago, everything changed when he began organizing survival training and log-cabin tours for tourists in his forest. As they marveled at the majestic trees, the enchanted curiosity of their gaze reawakened his own and his childhood love of nature was rekindled. Around the same time, scientists began conducting research in his forest. Soon, every day became colored with wonderment and the thrill of discovery — no longer able to see trees as a currency, he instead saw them as the priceless living wonders that they are. He recounts:

Life as a forester became exciting once again. Every day in the forest was a day of discovery. This led me to unusual ways of managing the forest. When you know that trees experience pain and have memories and that tree parents live together with their children, then you can no longer just chop them down and disrupt their lives with large machines.

The revelation came to him in flashes, the most eye-opening of which happened on one of his regular walks through a reserve of old beech tree in his forest. Passing by a patch of odd mossy stones he had seen many times before, he was suddenly seized with a new awareness of their strangeness. When he bent down to examine them, he made an astonishing discovery:

The stones were an unusual shape: they were gently curved with hollowed-out areas. Carefully, I lifted the moss on one of the stones. What I found underneath was tree bark. So, these were not stones, after all, but old wood. I was surprised at how hard the “stone” was, because it usually takes only a few years for beechwood lying on damp ground to decompose. But what surprised me most was that I couldn’t lift the wood. It was obviously attached to the ground in some way. I took out my pocketknife and carefully scraped away some of the bark until I got down to a greenish layer. Green? This color is found only in chlorophyll, which makes new leaves green; reserves of chlorophyll are also stored in the trunks of living trees. That could mean only one thing: this piece of wood was still alive! I suddenly noticed that the remaining “stones” formed a distinct pattern: they were arranged in a circle with a diameter of about 5 feet. What I had stumbled upon were the gnarled remains of an enormous ancient tree stump. All that was left were vestiges of the outermost edge. The interior had completely rotted into humus long ago — a clear indication that the tree must have been felled at least four or five hundred years earlier.

How can a tree cut down centuries ago could still be alive? Without leaves, a tree is unable to perform photosynthesis, which is how it converts sunlight into sugar for sustenance. The ancient tree was clearly receiving nutrients in some other way — for hundreds of years.

Beneath the mystery lay a fascinating frontier of scientific research, which would eventually reveal that this tree was not unique in its assisted living. Neighboring trees, scientists found, help each other through their root systems — either directly, by intertwining their roots, or indirectly, by growing fungal networks around the roots that serve as a sort of extended nervous system connecting separate trees. If this weren’t remarkable enough, these arboreal mutualities are even more complex — trees appear able to distinguish their own roots from those of other species and even of their own relatives.

Art by Judith Clay from Thea’s Tree

Wohlleben ponders this astonishing sociality of trees, abounding with wisdom about what makes strong human communities and societies:

Why are trees such social beings? Why do they share food with their own species and sometimes even go so far as to nourish their competitors? The reasons are the same as for human communities: there are advantages to working together. A tree is not a forest. On its own, a tree cannot establish a consistent local climate. It is at the mercy of wind and weather. But together, many trees create an ecosystem that moderates extremes of heat and cold, stores a great deal of water, and generates a great deal of humidity. And in this protected environment, trees can live to be very old. To get to this point, the community must remain intact no matter what. If every tree were looking out only for itself, then quite a few of them would never reach old age. Regular fatalities would result in many large gaps in the tree canopy, which would make it easier for storms to get inside the forest and uproot more trees. The heat of summer would reach the forest floor and dry it out. Every tree would suffer.

Every tree, therefore, is valuable to the community and worth keeping around for as long as possible. And that is why even sick individuals are supported and nourished until they recover. Next time, perhaps it will be the other way round, and the supporting tree might be the one in need of assistance.

[…]

A tree can be only as strong as the forest that surrounds it.

One can’t help but wonder whether trees are so much better equipped at this mutual care than we are because of the different time-scales on which our respective existences play out. Is some of our inability to see this bigger picture of shared sustenance in human communities a function of our biological short-sightedness? Are organisms who live on different time scales better able to act in accordance with this grander scheme of things in a universe that is deeply interconnected?

To be sure, even trees are discriminating in their kinship, which they extend in varying degrees. Wohlleben explains:

Every tree is a member of this community, but there are different levels of membership. For example, most stumps rot away into humus and disappear within a couple of hundred years (which is not very long for a tree). Only a few individuals are kept alive over the centuries… What’s the difference? Do tree societies have second-class citizens just like human societies? It seems they do, though the idea of “class” doesn’t quite fit. It is rather the degree of connection — or maybe even affection — that decides how helpful a tree’s colleagues will be.

These relationships, Wohlleben points out, are encoded in the forest canopy and visible to anyone who simply looks up:

The average tree grows its branches out until it encounters the branch tips of a neighboring tree of the same height. It doesn’t grow any wider because the air and better light in this space are already taken. However, it heavily reinforces the branches it has extended, so you get the impression that there’s quite a shoving match going on up there. But a pair of true friends is careful right from the outset not to grow overly thick branches in each other’s direction. The trees don’t want to take anything away from each other, and so they develop sturdy branches only at the outer edges of their crowns, that is to say, only in the direction of “non-friends.” Such partners are often so tightly connected at the roots that sometimes they even die together.

Art by Cécile Gambini from Strange Trees by Bernadette Pourquié

But trees don’t interact with one another in isolation from the rest of the ecosystem. The substance of their communication, in fact, is often about and even to other species. Wohlleben describes their particularly remarkable olfactory warning system:

Four decades ago, scientists noticed something on the African savannah. The giraffes there were feeding on umbrella thorn acacias, and the trees didn’t like this one bit. It took the acacias mere minutes to start pumping toxic substances into their leaves to rid themselves of the large herbivores. The giraffes got the message and moved on to other trees in the vicinity. But did they move on to trees close by? No, for the time being, they walked right by a few trees and resumed their meal only when they had moved about 100 yards away.

The reason for this behavior is astonishing. The acacia trees that were being eaten gave off a warning gas (specifically, ethylene) that signaled to neighboring trees of the same species that a crisis was at hand. Right away, all the forewarned trees also pumped toxins into their leaves to prepare themselves. The giraffes were wise to this game and therefore moved farther away to a part of the savannah where they could find trees that were oblivious to what was going on. Or else they moved upwind. For the scent messages are carried to nearby trees on the breeze, and if the animals walked upwind, they could find acacias close by that had no idea the giraffes were there.

Because trees operate on time scales dramatically more extended than our own, they operate far more slowly than we do — their electrical impulses crawl at the speed of a third of an inch per minute. Wohlleben writes:

Beeches, spruce, and oaks all register pain as soon as some creature starts nibbling on them. When a caterpillar takes a hearty bite out of a leaf, the tissue around the site of the damage changes. In addition, the leaf tissue sends out electrical signals, just as human tissue does when it is hurt. However, the signal is not transmitted in milliseconds, as human signals are; instead, the plant signal travels at the slow speed of a third of an inch per minute. Accordingly, it takes an hour or so before defensive compounds reach the leaves to spoil the pest’s meal. Trees live their lives in the really slow lane, even when they are in danger. But this slow tempo doesn’t mean that a tree is not on top of what is happening in different parts of its structure. If the roots find themselves in trouble, this information is broadcast throughout the tree, which can trigger the leaves to release scent compounds. And not just any old scent compounds, but compounds that are specifically formulated for the task at hand.

The upside of this incapacity for speed is that there is no need for blanket alarmism — the recompense of trees’ inherent slowness is an extreme precision of signal. In addition to smell, they also use taste — each species produces a different kind of “saliva,” which can be infused with different pheromones targeted at warding off a specific predator.

Wohlleben illustrates the centrality of trees in Earth’s ecosystem with a story about Yellowstone National Park that demonstrates “how our appreciation for trees affects the way we interact with the world around us”:

It all starts with the wolves. Wolves disappeared from Yellowstone, the world’s first national park, in the 1920s. When they left, the entire ecosystem changed. Elk herds in the park increased their numbers and began to make quite a meal of the aspens, willows, and cottonwoods that lined the streams. Vegetation declined and animals that depended on the trees left. The wolves were absent for seventy years. When they returned, the elks’ languorous browsing days were over. As the wolf packs kept the herds on the move, browsing diminished, and the trees sprang back. The roots of cottonwoods and willows once again stabilized stream banks and slowed the flow of water. This, in turn, created space for animals such as beavers to return. These industrious builders could now find the materials they needed to construct their lodges and raise their families. The animals that depended on the riparian meadows came back, as well. The wolves turned out to be better stewards of the land than people, creating conditions that allowed the trees to grow and exert their influence on the landscape.

Art by William Grill from The Wolves of Currumpaw

This interconnectedness isn’t limited to regional ecosystems. Wohlleben cites the work of Japanese marine chemist Katsuhiko Matsunaga, who discovered that trees falling into a river can change the acidity of the water and thus stimulate the growth of plankton — the elemental and most significant building block of the entire food chain, on which our own sustenance depends.

In the remainder of The Hidden Life of Trees, Wohlleben goes on to explore such fascinating aspects of arboreal communication as how trees pass wisdom down to the next generation through their seeds, what makes them live so long, and how forests handle immigrants. Complement it with this wonderful illustrated atlas of the world’s strangest trees and an 800-year visual history of trees as symbolic diagrams.

BP

Relationship Lessons from Trees

“I think of good love as something that roots, not rots, over time, and of the hyphae that are weaving through the ground below me, reaching out through the soil in search of mergings.”

Relationship Lessons from Trees

“The tree which moves some to tears of joy is in the eyes of others only a green thing which stands in the way,” William Blake wrote in his most beautiful letter. “As a man is, so he sees.” Walt Whitman saw trees as the wisest of teachers; Hermann Hesse as our mightiest consolation for mortality. Wangari Maathai rooted in them a colossal act of resistance that earned her the Nobel Peace Prize. Poets have elegized their wisdom, artists have drawn from their form resonance with our human emotions, scientists are only just beginning to uncover their own secret language.

Robert Macfarlane — a rare enchanter who entwines the scientific and the poetic in his lyrical explorations of the natural world — offers a crowning curio in the canon of wisdom on human life drawn from trees in a passage from Underland: A Deep Time Journey (public library) — his magnificent soul-guided, science-lit tour of the hidden universe beneath our feet.

Art by Arthur Rackham for a rare 1917 edition of the Brothers Grimm fairy tales. (Available as a print.)

Macfarlane writes:

Lying there among the trees, despite a learned wariness towards anthropomorphism, I find it hard not to imagine these arboreal relations in terms of tenderness, generosity and even love: the respectful distance of their shy crowns, the kissing branches that have pleached with one another, the unseen connections forged by root and hyphae between seemingly distant trees. I remember something Louis de Bernières has written about a relationship that endured into old age: “we had roots that grew towards each other underground, and when all the pretty blossom had fallen from our branches we found that we were one tree and not two.” As someone lucky to live in a long love, I recognize that gradual growing-towards and subterranean intertwining; the things that do not need to be said between us, the unspoken communication which can sometimes tilt troublingly towards silence, and the sharing of both happiness and pain. I think of good love as something that roots, not rots, over time, and of the hyphae that are weaving through the ground below me, reaching out through the soil in search of mergings. Theirs, too, seems to me then a version of love’s work.

Art from Trees at Night by Art Young, 1926. (Available as a print.)

Beneath the canopy, Macfarlane marvels at the slim contour of empty space around each tree’s crown — a phenomenon known as crown shyness, “whereby individual forest trees respect each other’s space, leaving slender running gaps between the end of one tree’s outermost leaves and the start of another’s.”

In this, too, I see a poignant lesson in love, evocative of Rilke and what may be the greatest relationship advice ever committed to words: “I hold this to be the highest task of a bond between two people: that each should stand guard over the solitude of the other.”

“Broken/hearted” by Maria Popova. (Available as a print.)

Couple this tiny fragment of the sweepingly wondrous Underland with Amanda Palmer’s lovely reading of Mary Oliver’s poem “When I Am Among the Trees,” then revisit Kahlil Gibran on the difficult balance of intimacy and independence in love.

BP

The Fascinating Science of How Trees Communicate, Animated

“Trees are the foundation of forests, but a forest is much more than what you see.”

“The tree which moves some to tears of joy is in the eyes of others only a green thing which stands in the way,” William Blake wrote in his most beautiful letter. Walt Whitman found in trees a model of existential authenticity. Hermann Hesse saw them as the wisest of teachers. Wangari Maathai won the Nobel Peace Prize for her noble work of planting trees as resistance and empowerment.

But trees are much more than what they are to us, or for us, or in relation to us. They are relational miracles all their own, entangled in complex, symbiotic webs of interbeing, constantly communicating with one another through chemical signals dispatched along the fungal networks that live in their roots — an invisible, astonishing underworld only recently discovered, thanks to the work of Canadian forest ecologist Suzanne Simard.

In this lovely short animation from TED-Ed and animator Avi Ofer, Camille Defrenne — one of Simard’s doctoral students at the University of British Columbia, studying how the interaction and architecture of root systems relate to forest dynamics and climate change — synthesizes the fascinating, almost otherworldly findings of Simard’s lab:

Simard, whose research was foundational to German forester Peter Wohlleben’s wildly popular book The Hidden Life of Trees: What They Feel, How They Communicate, discusses her work and the improbable path that led her to it in her wonderful full-length TED talk:

Yes, trees are the foundation of forests, but a forest is much more than what you see… Underground there is this other world — a world of infinite biological pathways that connect trees and allow them to communicate and allow the forest to behave as though it’s a single organism. It might remind you of a sort of intelligence.

Complement with a wondrous picture-book about the forest, Annie Dillard on how mangrove trees illuminate the human search for meaning, and biologist David Haskell on what a dozen of the world’s most unusual trees taught him about the art of relationship, then revisit three other lovely animations by Avi Ofer: Neil Gaiman’s existentialist dream (also involving trees) narrated by Amanda Palmer; Jane Goodall on her remarkable life-story; and philosopher Skye Clearly on why we love.

BP

Ecologist and Philosopher David Abram on the Language of Nature and the Secret Wisdom of the More-Than-Human World

“We are human only in contact, and conviviality, with what is not human.”

Ecologist and Philosopher David Abram on the Language of Nature and the Secret Wisdom of the More-Than-Human World

“We need another and a wiser and perhaps a more mystical concept of animals,” the great nature writer Henry Beston wrote in 1928 as he contemplated belonging and the web of life. “In a world older and more complete than ours they move finished and complete, gifted with extensions of the senses we have lost or never attained, living by voices we shall never hear.” The geologist Hans Cloos, a contemporary of Beston’s, complemented the sentiment beautifully in reflecting on our conversations with the planet: “We translate the earth’s language into our own, and enrich the already bright and colorful surface of the present with the knowledge of the inexhaustible abundance of the past.”

As we learn to translate the language of nature, there is more than mere astonishment at what we uncover; at the knowledge — nascent to science, ancient to native cultures the world over — of what trees feel and how they communicate, or of how other animal consciousnesses experience the world. There is magic — the realest, rawest form of magic we can access in an unsuperstitious world grounded in science but willing to soar beyond it, into other, non-materialist modes of perception.

That is what ecologist and philosopher David Abram explores with equal parts scientific curiosity and reverence for native wisdom in The Spell of the Sensuous: Perception and Language in a More-Than-Human World (public library).

Art by Jackie Morris from The Lost Words by Robert MacFarlane — a visual dictionary of poetic spells reclaiming nature’s language

Abram writes:

Magic… in its perhaps most primordial sense, is the experience of existing in a world made up of multiple intelligences, the intuition that every form one perceives — from the swallow swooping overhead to the fly on a blade of grass, and indeed the blade of grass itself — is an experiencing form, an entity with its own predilections and sensations, albeit sensations that are very different from our own.

[…]

Caught up in a mass of abstractions, our attention hypnotized by a host of human-made technologies that only reflect us back to ourselves, it is all too easy for us to forget our carnal inherence in a more-than-human matrix of sensations and sensibilities. Our bodies have formed themselves in delicate reciprocity with the manifold textures, sounds, and shapes of an animate earth — our eyes have evolved in subtle interaction with other eyes, as our ears are attuned by their very structure to the howling of wolves and the honking of geese. To shut ourselves off from these other voices, to continue by our lifestyles to condemn these other sensibilities to the oblivion of extinction, is to rob our own senses of their integrity, and to rob our minds of their coherence. We are human only in contact, and conviviality, with what is not human.

Illustration by Arthur Rackham for a rare 1917 edition of the Brothers Grimm fairy tales. (Art available as a print.)

And yet a defining feature of what makes us human — our imagination — is predicated on a recognition of this sensorial interrelation. Two centuries after William Blake wrote in his searing defense of the imagination that “the tree which moves some to tears of joy is in the eyes of others only a green thing which stands in the way, [for] as a man is, so he sees,” Abram writes:

That which we call imagination is from the first an attribute of the senses themselves; imagination is not a separate mental faculty (as we so often assume) but is rather the way the senses themselves have of throwing themselves beyond what is immediately given, in order to make tentative contact with the other sides of things that we do not sense directly, with the hidden or invisible aspects of the sensible.

Echoing naturalist John Muir’s poetic observation that “when we try to pick out anything by itself, we find it hitched to everything else in the universe” and philosopher Alan Watts’s admonition that “Life and Reality are not things you can have for yourself unless you accord them to all others,” Abram considers the relationship between perception, sensation, and reality beyond our isolated experience:

The “real world” in which we find ourselves, then — the very world our sciences strive to fathom — is not a sheer “object,” not a fixed and finished “datum” from which all subjects and subjective qualities could be pared away, but is rather an intertwined matrix of sensations and perceptions, a collective field of experience lived through from many different angles. The mutual inscription of others in my experience, and (as I must assume) of myself in their experiences, effects the interweaving of our individual phenomenal fields into a single, ever-shifting fabric, a single phenomenal world or “reality.”

And yet, as we know from our everyday experience, the phenomenal world is remarkably stable and solid; we are able to count on it in so many ways, and we take for granted much of its structure and character. This experienced solidity is precisely sustained by the continual encounter with others, with other embodied subjects, other centers of experience. The encounter with other perceivers continually assures me that there is more to any thing, or to the world, than I myself can perceive at any moment. Besides that which I directly see of a particular oak tree or building, I know or intuit that there are also those facets of the oak or building that are visible to the other perceivers that I see. I sense that that tree is much more than what I directly see of it, since it is also what the others whom I see perceive of it; I sense that as a perceivable presence it already existed before I came to look at it, and indeed that it will not dissipate when I turn away from it, since it remains an experience for others — not just for other persons, but… for other sentient organisms, for the birds that nest in its branches and for the insects that move along its bark, and even, finally, for the sensitive cells and tissues of the oak itself, quietly drinking sunlight through its leaves. It is this informing of my perceptions by the evident perceptions and sensations of other bodily entities that establishes, for me, the relative solidity and stability of the world.

Illustration by Matthew Forsythe from The Golden Leaf

This recognition of the reality of other experiences calls to mind the distinction philosopher Martin Buber drew nearly a century earlier between the I-It and I-Thou orientations toward what is other than oneself. And this recognition, Abram argues, is the key to redeeming our connection to the rest of nature and the more-than-human world, so artificially severed in modern Western culture. “We call it ‘Nature’; only reluctantly admitting ourselves to be ‘Nature’ too,” Denise Levertov captured this modern hijacking of our essence in her exquisite poem “Sojourns in the Parallel World.” Abram considers what it takes for us to heal the artificial severance into parallels and re-intersect our own experience with the manifold realities of that “other” world:

Direct, prereflective perception is inherently synaesthetic, participatory, and animistic, disclosing the things and elements that surround us not as inert objects but as expressive subjects, entities, powers, potencies. And yet most of us seem, today, very far from such experience. Trees rarely, if ever, speak to us; animals no longer approach us as emissaries from alien zones of intelligence; the sun and the moon no longer draw prayers from us but seem to arc blindly across the sky.

[…]

We may acknowledge, intellectually, our body’s reliance upon those plants and animals that we consume as nourishment, yet the civilized mind still feels itself somehow separate, autonomous, independent of the body and of bodily nature in general. Only as we begin to notice and to experience, once again, our immersion in the invisible air do we start to recall what it is to be fully a part of this world… This breathing landscape is no longer just a passive backdrop against which human history unfolds, but a potentized field of intelligence in which our actions participate.

In the remainder of the altogether enchanting The Spell of the Sensuous, Abrams visits with various native cultures to learn from their wisdom and mirror it back through the lens of a more-than-scientific understanding of the world. Complement it with a lovely illustrated dictionary of poetic spells reclaiming the language of nature, then revisit the great marine biologist and poetic science writer Rachel Carson, who awakened the modern ecological conscience, on science and our spiritual bond with nature.

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