The Hidden Life of Trees: What They Feel, How They Communicate — Discoveries from a Secret World

by Peter Wohlleben

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.

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.

Planted forests, which is what most of the coniferous forests in Central Europe are, behave more like the street kids I describe in chapter 27. Because their roots are irreparably damaged when they are planted, they seem almost incapable of networking with one another. As a rule, trees in planted forests like these behave like loners and suffer from their isolation. Most of them never have the opportunity to grow old anyway. Depending on the species, these trees are considered ready to harvest when they are only about a hundred years old.

Salicylic acid is a precursor of aspirin, and tea made from willow bark can relieve headaches and bring down fevers.

One teaspoon of forest soil contains many miles of these “hyphae.”8 Over centuries, a single fungus can cover many square miles and network an entire forest. The fungal connections transmit signals from one tree to the next, helping the trees exchange news about insects, drought, and other dangers. Science has adopted a term first coined by the journal Nature for Dr. Simard’s discovery of the “wood wide web” pervading our forests.9

when we step into farm fields, the vegetation becomes very quiet. Thanks to selective breeding, our cultivated plants have, for the most part, lost their ability to communicate above or below ground—you could say they are deaf and dumb—and therefore they are easy prey for insect pests.12 That is one reason why modern agriculture uses so many pesticides. Perhaps farmers can learn from the forests and breed a little more wildness back into their grain and potatoes so that they’ll be more talkative in the future.

So trees communicate by means of olfactory, visual, and electrical signals. (The electrical signals travel via a form of nerve cell at the tips of the roots.)

They started listening, and it didn’t take them long to discover that their measuring apparatus was registering roots crackling quietly at a frequency of 220 hertz. Crackling roots? That doesn’t necessarily mean anything. After all, even dead wood crackles when it’s burned in a stove. But the noises discovered in the laboratory caused the researchers to sit up and pay attention. For the roots of seedlings not directly involved in the experiment reacted. Whenever the seedlings’ roots were exposed to a crackling at 220 hertz, they oriented their tips in that direction. That means the grasses were registering this frequency, so it makes sense to say they “heard” it.

The process of learning stability is triggered by painful micro-tears that occur when the trees bend way over in the wind, first in one direction and then in the other. Wherever it hurts, that’s where the tree must strengthen its support structure. This takes a whole lot of energy, which is then unavailable for growing upward. A

In exchange for the rich sugary reward, the fungi provide a few complimentary benefits for the tree, such as filtering out heavy metals, which are less detrimental to the fungi than to the tree’s roots. These diverted pollutants turn up every fall in the pretty fruiting bodies we bring home in the form of porcini, cèpe, or bolete mushrooms. No wonder radioactive cesium, which was found in soil even before the nuclear reactor disaster in Chernobyl in 1986, is mostly found in mushrooms.

There are more life forms in a handful of forest soil than there are people on the planet.