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

by Peter Wohlleben

One reason that many of us fail to understand trees is that they live on a different time scale than us.

The electrical impulses that pass through the roots of trees, for example, move at the slow rate of one third of an inch per second.

But the most astonishing thing about trees is how social they are. The trees in a forest care for each other, sometimes even going so far as to nourish the stump of a felled tree for centuries after it was cut down by feeding it sugars and other nutrients, and so keeping it alive.

The reason trees share food and communicate is that they need each other. It takes a forest to create a microclimate suitable for tree growth and sustenance. So it’s not surprising that isolated trees have far shorter lives than those living connected together in forests.

This book is a lens to help you take a closer look at what you might have taken for granted. Slow down, breathe deep, and look around. What can you hear? What do you see? How do you feel?

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.

forests are superorganisms with interconnections much like ant colonies.

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.

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.

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.

Trees, it turns out, have a completely different way of communicating: they use scent.

For example, 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.

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 spe...

Accordingly, it takes an hour or so before defensive compounds reach the leaves t...

When it comes to some species of insects, trees can accurately identify which bad guys they are up against. The saliva of each species is different, and trees can match the saliva to the insect. Indeed, the match can be so precise that trees can release pheromones that summon specific beneficial predators.

For if they can identify saliva, they must also have a sense of taste.

In the symbiotic community of the forest, not only trees but also shrubs and grasses—and possibly all plant species—exchange information this way. However, 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.

When trees grow together, nutrients and water can be optimally divided among them all so that each tree can grow into the best tree it can be. If you “help” individual trees by getting rid of their supposed competition, the remaining trees are bereft. They send messages out to their neighbors in vain, because nothing remains but stumps.

This is because a tree can be only as strong as the forest that surrounds

A break in its bark, then, is at least as uncomfortable for a tree as a wound in our skin is for us. And, therefore, the tree relies on mechanisms similar to the ones we use to stop this from happening.

I’m talking about dwarf trees on the tundra, which are sometimes trampled to death by travelers who don’t even know they are there. It can take these trees a hundred years to grow just 8 inches tall.

Every being has its niche and its function, which contribute

Grizzly bears hibernate and so do dormice. But trees? Do they experience anything that could be compared to our nightly time-outs? The grizzly bear is a good candidate for comparison, because it follows a similar strategy to trees. In summer and early fall, it eats to lay down a thick layer of fat it can live off all winter. And this is exactly what our trees do as well. Of course, they don’t feed on blueberries or salmon, but they fuel themselves with energy from the sun, which they use to make sugar and other compounds they can hold in reserve. And they store these under their skin just like a bear. Because they can’t get any fatter (only their bones—that is to say, their wood—can grow), the best they can do is fill their tissues with food. And whereas bears can go on eating everything they can find, at some point, the trees get full.

In particularly warm years, with high fall temperatures, you can find trees whose sense of time has become confused. Their buds swell in September, and a few trees even put out new leaves. Trees that get in a muddle like this have to suffer the consequences when delayed frosts finally arrive.

a deciduous tree has to shed its leaves. But when is the optimal moment? Trees cannot anticipate the coming winter. They don’t know whether it is going to be harsh or mild. All they register are shortening days and falling temperatures.

Every year, a live tree adds a growth ring to the wood in its trunk because it is, you could say, damned to grow whether it wants to or not.

FOREST AIR IS the epitome of healthy air. People who want to take a deep breath of fresh air or engage in physical activity in a particularly agreeable atmosphere step out into the forest. There’s every reason to do so. The air truly is considerably cleaner under the trees, because the trees act as huge air filters.

Their leaves and needles hang in a steady breeze, catching large and small particles as they float by. Per year and square mile this can amount to 20,000 tons of material.

Coniferous forests noticeably reduce the number of germs in the air, which feels particularly good to people who suffer from allergies.

Korean scientists have been tracking older women as they walk through forests and urban areas. The result? When the women were walking in the forest, their blood pressure, their lung capacity, and the elasticity of their arteries improved, whereas an excursion into town showed none of these changes. It’s possible that phytoncides have a beneficial effect on our immune systems as well as the trees’ health, because they kill germs. Personally, however, I think the swirling cocktail of tree talk is the reason we enjoy being out in the forest so much. At least when we are out in undisturbed forests.

IN THESE TIMES of dramatic environmental upheaval, our yearning for undisturbed nature is increasing.