One cold afternoon in the autumn of 2018, in a forest outside the tiny village of Hümmel, in Rhineland-Palatinate, I went for a walk with the German forester Peter Wohlleben. He’s a tall man with a long head and a short gray beard; his vanishing hair was shaved close to the skull. He had the slightly stiff bearing of a person who thinks often about the importance of uprightness. (“When a structure is nice and vertical, it is difficult to upset its equilibrium,” he has written, of trees.) He wore muddy, size-15 army boots and a black fleece jacket that smelled of old woodsmoke.
We followed a logging road through a forest of beeches. Up in the canopy, the leaves were every possible hue of apple skin. Wohlleben had been managing the forest for the municipality for almost three decades, and he had cared for it with unusual gentleness. Each tree is cut individually and removed using horses, rather than heavy machinery, to avoid damaging underground networks of roots and fungi that allow trees to exchange resources and chemical signals. He has generated additional income for the forest by leading tours, teaching courses, and creating a forest cemetery, where people’s ashes can be buried in an urn made of untreated beech wood. He has long insisted that people around the world could and should manage their forests likewise. Until a few years ago, virtually no one was listening.
In 2007, to propagate his views and his know-how, Wohlleben began writing books, hammering them out at a rate of one or two a year. His first fifteen reached a modest audience. He later realized that this is likely because they were written in a “minor key.” They had titles such as “Forest Without Guardians: In the Stranglehold of Hunting Interests and Forestry” and “The Forest: An Obituary.” Following a period of depression due to overwork, he decided to change his tone. His sixteenth book, “The Hidden Life of Trees,” from 2015, was written in a major key—warmly avuncular, storybook simple, and heavily dusted with the glitter of wonderment. It focussed on new and not-so-new scientific findings indicating the sociality and sensuous interiority of trees. His publisher scheduled a print run of twenty-seven hundred copies. For reasons that Wohlleben is still trying to make sense of, the book bloomed, then exploded: it has sold more than a million copies in Germany alone, and more than three million worldwide. Wohlleben now has his own magazine, which features his face on every cover, Oprah-style; a podcast; a film documentary; and a TV show, in which he takes German celebrities on overnight survival trips. He was recently invited to speak before the European Commission, and he has consulted with Germany’s Green Party leaders about their forest policy.
“The Hidden Life of Trees” grew directly out of walking tours like the one that Wohlleben was leading me on, through the same tract of woods. “The people I guided through the forest—they were hard trainers,” he said. “Because, when I talked in a way that wasn’t interesting, they would begin talking with each other.” Eschewing technical jargon, he learned how to make them laugh and how to make them gasp.
He stooped and gently grasped a sapling between his fingers; the thickness of its trunk was somewhere between a pencil and a strand of bucatini. He asked me how old I thought it was.
“Ten years?” I guessed.
Wohlleben carefully counted the bud nodes along one of its branches.
“One hundred and twenty years,” he said.
I should have seen this surprise coming; he describes the phenomenon in detail in his book. The growth process of beech trees follows a pattern that German foresters call “education by shade”: the “mother trees” keep their offspring small for decades before finally toppling over, allowing them to shoot skyward. Wohlleben is fanatical about the virtues of slow growth. The more slowly a tree grows, he says, the tighter its grain, and the greater its chances of surviving natural threats. It pains him to see fast-growing trees in single-species plantations lost to pest infestations and storms. Given all that we now know about how forests work, to clear-cut an old forest and replace it with a monocrop is “evil,” he said.
When Wohlleben entered forestry school, in the early eighties, he did so believing that the profession was “something like a tree-keeper,” and was dismayed to learn that it was more like being an industrial farmer. In Germany, forests were regularly clear-cut, poisoned with herbicides such as 2, 4, 5-Trichlorophenoxyacetic acid (an active ingredient in Agent Orange), and then replanted with nonnative conifers. Forestry practice has changed since then—clear-cutting and the use of herbicides have been strictly curtailed—but not enough for Wohlleben.
Near the end of our walk, he led me over to a hollowed-out, C-shaped ring of mossy wood protruding from the soil. “That is the stump from an old tree,” he said. I knelt down and felt it. It had the hard, wet heft of green wood. It had been cut down at least fifty years ago, and yet, somehow, it was still alive. The tree’s roots, many of which protruded above the soil, were visibly connected to a nearby beech tree.
To Wohlleben, this was proof of the remarkable mutuality of beeches—that they will continue caring for nearby trees even after their death. “The Hidden Life of Trees” begins by describing the day that Wohlleben discovered a stump much like this one, which had been “felled at least four or five hundred years earlier.” It had likewise been kept alive all that time by its neighbors. On our walk, we had been discussing his belief that trees are intelligent—that they make decisions, feel pain, have affinities, and, perhaps, consciously experience the world. I pointed out that, in a Darwinian sense, it seemed distinctly unintelligent to keep feeding a corpse for five hundred years.
“But it’s not dead, that’s exactly it,” he replied. “Only the part with the solar cells has been cut down. Perhaps the real tree is underground.”
“And something about those roots staying alive is also beneficial to this tree?” I asked, gesturing to the living tree beside it.
“We don’t know. That’s a typical human question. What’s the benefit for this tree? ‘Support without benefit? That’s not possible!’ ” he said, in a gently mocking tone. He hazarded a guess that the stump had retained a sort of genetic memory of past hardships—a thousand years of fire and ice, pests and pestilence, drought and flood, storm and stress—which it was able to share with the other tree via the roots. Or, he said, “Perhaps it’s just to be social.”
Wohlleben’s thought tends to move like the body of a fencer—he lunges forward, past his center of gravity, then just as quickly retreats, before thrusting again. In “The Hidden Life of Trees” he writes that, “when trees are really thirsty, they begin to scream.” He admits that this is probably “a purely mechanical event”; this sound, which can be heard only by using special instruments, is in fact an ultrasonic vibration occurring in the trunk as its vascular system struggles to transport a scarce water supply up to the leaves. (Imagine a straw slurping at the dregs of a milkshake and you’re close to envisioning it.) And yet, he writes, “if we were to look through a microscope to examine how humans produce sounds, what we would see wouldn’t be that different: the passage of air down the windpipe causes our vocal cords to vibrate.” He posits a theory: “The trees might be screaming out a dire warning to their colleagues that water levels are running low.” The purpose of this verbal sleight of hand is to humanize trees, and thereby impel the reader to extend greater care to them. To this end, Wohlleben often overreaches; in one of the book’s more nonsensical moments, he explains that some trees can detect animal saliva and therefore concludes that trees must “have a sense of taste,” which is roughly equivalent to saying that, because a cat can hear a bat squeaking, the cat is also capable of echolocation.
Wohlleben is aware of the scientific pitfalls of his method, but he excuses it as a well-intended effort to widen the reader’s imagination in ways that most scientists are institutionally and constitutionally incapable of doing. His critics, meanwhile, see it as a kind of intellectual hucksterism. “With that approach, you could say anything!” Jürgen Bauhus, a professor of silviculture at the University of Freiburg, said, when I described Wohlleben’s just-asking-questions defense. Take, for example, the zombified beech stump that Wohlleben had shown me. Bauhus put forward a leaner theory: the other trees are not sustaining that stump to glean its memories; they are keeping it alive to draw water through its vast root system, an act of pure, unthinking opportunism.
Bauhus calls “The Hidden Life of Trees” a “very nice storybook. But that’s it.” Other scientists speak of it in harsher terms. Barbara Hawkins, a professor who specializes in tree physiology, told me it was “fanciful.” Suzanne Simard, a professor of forest ecology who is famous for her research into tree sociality, and who recently published a memoir titled “Finding the Mother Tree,” told me, “Some of the anthropomorphizing was just over the top. Even I was, like, ‘Ugh, I can’t read this.’ ” Graeme P. Berlyn, a professor of forest management, wrote to me, “There are a lot of amazing things about trees and their interactions with their environment, but I see little of value in Wohlleben’s fantasies.” One German scientist was bothered enough to circulate a petition decrying Wohlleben’s “fairy tales,” which garnered more than forty-five hundred signatures; the trained biologist Torben Halbe even published a book-length critique titled “The Real Life of Trees.” These critics appear to be a vocal sliver of a mostly silent scientific majority—in the introduction to Halbe’s book, Nikolaus Amrhein, a professor of plant physiology, writes, “Most of my colleagues, if they have read the book at all, consider Wohlleben’s theses so obviously unscientific and untenable that they do not find it necessary to express themselves critically in public.”
Wohlleben’s detractors have three main objections to his work. First, he humanizes trees, a cardinal sin in popular science writing dating back at least to the “nature fakers” debate of the early nineteen-hundreds. Second, they charge that Wohlleben cherry-picks and exaggerates many of the scientific findings that underpin his book. And, lastly, they argue that he portrays forests as cartoonishly coöperative. Like Simard, Wohlleben is dedicated to counteracting the reductive understanding of Darwinism as a merciless, perpetual war of all against all. But, in doing so, he swaps a Hobbesian dystopia for a Merkelian utopia: a diverse society of almost-pacifists who work hard, talk softly, and share their wealth.
Arboreality is often much uglier than Wohlleben lets on. Black walnuts poison other plants with a natural herbicide called juglone; some eucalyptus trees continually shed their oily bark, fuelling fires that immolate their competitors; various species of fig tree plant themselves high in the branches of other trees, then slowly creep downward, either strangling the host tree or splitting it apart. Trees of all species shade the ground, depriving seedlings—including their own offspring—of light, allowing only the fittest to survive. “If humans were like trees, we would go into a hospital and eliminate ninety-nine per cent of the babies, and keep only the best ones,” Christian Messier, a professor of applied forest ecology, told me.
The shadier side of trees can occasionally be glimpsed in Wohlleben’s work, albeit in a tone of regretful admission. “Now, the beech is an amazingly socially oriented tree,” he writes, “but only when it comes to its own kind. Beeches harass other species, such as oaks, to such an extent that they weaken.” “Immigrants,” “foreigners,” and “interlopers,” to use Wohlleben’s words for nonnative species, struggle against “purebred European” species. “Genetic misfits” are “discarded.” If trees are held to be exemplars of human behavior—rather than opaque others, or projections of our own preoccupations—dark echoes abound.
Wohlleben’s newest book is “The Heartbeat of Trees,” a collection of essays loosely clustered around an arboreal theme. In it, he seems less interested in responding to his critics than in answering the questions of his readers. One chapter addresses the topic of hugging trees (they can’t feel it, but Wohlleben encourages the reader to do it anyway); another asks whether people can perceive the energy of trees (a common claim among the auras-and-crystals crowd). Wohlleben, who is vocally opposed to “esoteric” thinking, interprets the latter question literally. He concludes that if you were to climb to the top of a tree, where the voltage of electrostatic energy is higher, you might be able to detect a slight charge in the tips of your hair. The chapter, like much of the book, feels like a long climb for a bit of static.
The issue of climate change, the gravest long-term threat to both trees and humans, was largely absent from “The Hidden Life of Trees,” but, in the new book, Wohlleben confronts it directly. He is trenchant in his critique of tree plantations and wood-pellet-power plants, which claim to help the climate but, he argues, end up destabilizing it further. He is less percipient when it comes to solutions. “My own personal goal is that, in the future, we will protect the climate by using less while simultaneously allowing as many forests around the world as possible to revert to their natural state,” he writes. Putting aside the fact that oceans, wetlands, and grasslands together likely play a larger role than forests do in sequestering atmospheric carbon, this goal rests on a dubious assumption that big old trees, in their current locations, will withstand a cascade of ever-worsening planetary disasters. Ancient trees, from the cedars of Lebanon to the baobabs of Madagascar to the giant sequoias of California, are currently dying off in alarming numbers around the world. They are victims of, among other things (including drought, fire, insects), simple mechanics: the bigger a tree is, the more water it needs; the hotter the weather gets, the harder it sucks water from the soil; and, the harder it sucks, the greater the risk of an air bubble rupturing its vascular tissues. Meanwhile, forests—and every other biome on earth—continue to fall victim to simple market forces. It is notable that the word “capitalism” appears zero times in “The Heartbeat of Trees.” Ditto for its best-selling predecessor. For as much time as Wohlleben spends discussing roots, the deeper sources of our global crisis, and the radical changes needed to address it, go unexplored.