Peter Wohlleben’s “The Hidden Life of Trees”

Until recently I was quite sure that a broad difference between animals and plants was that animals, because they are mobile, readily interact with each other (flocking, pursuing, etc.) while plants, anchored to the ground, don’t do so because they can’t. Except to attract insect pollinators, plants, I thought, live a life of exquisite solo struggle, seeking only the sun and water.

I’ve been steadily learning how far off I was. German forester Peter Wohlleben’s popular book, The Hidden Life of Trees: What They Feel, How They Communicate, is the most compelling lesson yet.

Among his many descriptions of communication and mutual assistance is Wohlleben’s account of how trees defend not only themselves but also each other. Observers have noted, for example, that umbrella thorn acacias in the African savannah pumped toxins into their leaves when they felt giraffes nibbling on them. “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.” They passed by the nearest trees because the trees being nibbled, in addition to pumping a repellent, “gave off a warning gas that signaled to neighboring trees that a crisis was at hand.” The giraffes knew these trees would not taste any better and kept walking.

hidden life of trees (

Many trees also have the ability to call in the air force. Reacting to bites from hostile insects, such trees emit scents that attract predators that devour the pests. “For example, elms and pines call on small parasite wasps that lay their eggs inside leaf-eating caterpillars.” The growing larvae devour the caterpillars from the inside.

The book brims with information and appreciations of this kind. Three more examples:

  • Trees that spend their lives in the forest fare much better than trees raised in one place and then transplanted to the forest. “Because their roots are irreparably damaged,…they seem almost incapable of networking with one another.” Like “street kids,” they “behave like loners and suffer from their isolation.”
  • Time for trees is slow and long. Internally, they, like animals, send alerts to parts of their body via chemicals and electrical impulses. But in a tree the electrical impulses move only about a third of an inch per second. (In our bodies, pain signals move  through our nerves about two feet per second, muscle impulses a hundred times faster.) No wonder it seems to us that plants are unresponsive.
  • Conifers (evergreens) “keep all their green finery on their branches” throughout the winter and have been doing so for 270 million years. Then deciduous (leaf-bearing) trees came along 100 million years ago, growing and discarding annually millions of delicate green solar panels. Was this an improvement? Why go to all that trouble? Wohlleben asks. Because “By discarding their leaves, they avoid a critical force—winter storms.” Between high winds, muddy soil, and a surface area equivalent to that of a large sailboat, tall evergreens take a battering in European winters. Growing and then dropping their huge surface area every year proved well worth while for the leafy new comers.

Wohlleben’s liberal use of human descriptors to explain the actions of trees delights many readers and annoys others. Andrea Wulf, in her review of the book, has both reactions.

I’m usually not keen on anthropomorphizing nature—and here trees are “nursing their babies” and having “a long, leisurely breakfast in the sun” while…fungus mushrooms are “rascals” who steal sugar and nutrients. These cutesy expressions make me cringe….But I have to admit that Wohlleben pulls it off—most of the time—because he sticks with scientific research and has a knack for making complex biology simple and thoroughly enjoyable.

I agree. While the vocabulary may bestow on trees a dignity and affection that we usually reserve for our own kind, it is scientists’ growing understanding of trees that creates the real story here. At a time of rapid environmental change, the book is as fascinating a revelation as one could ask for that life is even more intricate and purposeful than we knew.

Cooperation and Competition

In The Origin of Species, Darwin built his argument about natural selection in part from what people already knew full well about combatting the elements and competing with other people. Competition—political, economic, social, biological—has long been one of the prominent descriptors of life. We apply the concept easily and often to life’s many difficulties.

By comparison, references to the happier notions of cooperation and helping others seem sparse. People may use them to describe such special experiences as a team effort or the rebuilding of a community but not to depict the daily course of events. Most people would be unlikely to reply “cooperation” in answer to the question, “What word best describes the ordinary activities of your life?”


Social animals: an ant transports an aphid to the nest,

Cooperation deserves more credit than it gets. It merits equal weight (if not more) with competition in naming the most common dynamics among living things.

There are many reasons why cooperation doesn’t get that attention. One is that it is overshadowed by the related notion of “helping others.” Helping others, altruism, is a virtue enshrined in every religion and philosophy. Reaching out beyond our usual circle to those in need, with no expectation of obvious material reward, ranks at the height of human worthiness.

Mere “cooperation,” on the other hand, is often seen as “ordinary life.” It is certainly inseparable from the social lives of not only humans but many animals as well.  Some female birds, for example, assist their sisters in caring for the sister’s brood. Ants, wild dogs, egrets, gibbons and others sometimes share their food with a group. Chimpanzees raise a clamor when a fruit tree is discovered in order to bring other chimps to the feast. Cooperation is basic.

bird sharing

A bird offers to share;

One reason that it is basic is that it is more efficient than other social interactions in terms of cost and benefits for the participants. Competition, for example, leaves one party better off and the other worse off. Altruism is puzzling to scientists because the altruist appears to put himself at a disadvantage (he may donate money, for instance) while the recipient becomes better off than before. Cooperation, on the other hand, means that both parties clearly come out ahead. No one loses.

Cooperation is important, in other words, because it is more advantageous in the economy of social benefits than either altruism or competition.

There are complications and exceptions, of course. Just how beneficial cooperation turns out to actually be depends on who and what someone is cooperating with. Many people willingly cooperate with groups that cause harm and cooperation may be synonymous with the worst kind of obedience to an abusive authority figure.

red cross

and local Red Cross staff distribute food.

Still, it is utterly ordinary, run-of-the-mill cooperation that provides much of the essential maintenance of life. For humans, sharing daily chores in the kitchen, coordinating plans at work, reaching agreements with anybody on anything, and giving assistance, advice, or encouragement to others—all form the bright fabric of each of our days. To say of cooperation that it is “just life” is to pay it the highest compliment.

As we seek to understand our values, many people think that science is an inappropriate area in which to search. Science is about facts and hypotheses, not about what is desirable and undesirable. That is oversimplified. Evolutionary biology and psychology, along with history, provide a map of the circumstances of living that have fostered life or degraded it. Cooperation occupies a huge portion of the beneficial region on this map, an area so large that it is easy to overlook.