The Hidden Life of Trees summary

Trees aren’t only an essential part of our global climate; they’re also the basis for the soil in which we grow our food. And they interact with the earth’s soil in many different ways.

Surprisingly, the majority of the earth’s soil is comprised of trees. When our planet was formed, there wasn’t much around: there were minerals (for instance, cliffs and rocks), and air and water. Beaten by wind and rain, sections of these cliffs eroded and, over time, became a kind of gravel or sand. This is where single-celled organisms and algae settled.

Without trees, we’d have no water to drink, only bad air to breathe and hardly any soil. High time, then, to get acquainted with our arboreal friends! What does the life of a tree look like?

Let’s start at the beginning of a tree’s life. Every type of tree follows a different reproductive strategy. Some have small seeds that are disseminated by the wind. Others, such as oaks and chestnut trees, have larger seeds, which are usually transported with the help of animals.

Young trees don’t just grow; they develop a personality and, as the years pass, learn more about their environment and how they should best behave in it.

Personality, just as among people, varies among trees. Some are anxious, some bold. We tend to think of trees as doing nothing more than what we see them do. The weather turns cold, trees lose their leaves. Spring arrives, trees sprout buds and leaves. But it’s not that simple.

It’s good that trees can learn to cope with the threat of danger because they also like to talk about what they’ve learned. They do this in two ways: with scents and… with e-mail!

Trees can contact not only their own kind but also other creatures by using scent. Depending on the situation, they release different pheromones. They can be quite ingenious: when, for example, an elm tree or a Scots pine tree suffers a caterpillar infestation, the tree releases a scent that attracts a species of tiny wasp. These wasps fly to the affected tree and lay their eggs in the caterpillars; when these eggs hatch, the larvae attack and eat the caterpillars.

Trees aren’t dumb. They are dependent on their ecosystems and conspecifics and can get in touch with them. No wonder, then, that they help each other out whenever there’s trouble.

Trees often warn their conspecifics of potential dangers, by using scent and the “fungi-internet.” Mostly, that works very well. For example, on the African Savanna, where giraffes like to eat umbrella acacias. Within minutes of this happening to an acacia, it will release poison in its leaves and, at the same time, emits a warning gas – ethanol – that alerts other trees within a 100-meter radius of the attack.

We already saw that trees use fungi to spread information in the forest. The fungi do this via their mycelium – a network of thread-like filaments. But that’s not all: trees and fungi work together on other levels, too.

For instance, they help each other procure water and nutrients, a collaboration that starts when a fungus lets a few filaments grow into the roots of the tree. Then the process gets started: the fungus helps the tree absorb more water. Sometimes the ground is rather dry, and the tree can’t get enough water with its roots alone. The filaments of the fungus are much finer, allowing them to permeate more ground, drawing water and nutrients and passing them on to “their” tree.

We’ve seen how trees warn each other when, for example, beetles, giraffes or, a bit closer to home, deer attack. The injuries that trees sustain during such attacks are painful – and so, quite naturally, they want to avoid them at any cost.

There are different types of injury that a tree can suffer. And a major inflictor of these injuries are, of course, animals: deer eat young shoots, woodpeckers peck holes into the trunk and bark beetles drill through the bark and eat almost all of the living wood.

The image most people have of trees is dated. Unfortunately, the forestry industry is also behind the times. Traditional forestry, practiced almost everywhere in Germany today, does a few things wrong.

Of course, in the forestry industry, it’s mostly about producing wood. Foresters have long had a misconception: they thought that younger trees produce more wood faster than old trees. But this is untrue. Younger trees actually grow slower than older ones.