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

by Peter Wohlleben

Part of every rainfall is intercepted in the canopy and immediately evaporates again. In addition, each summer, trees use up to 8,500 cubic yards of water per square mile, which they release into the air through transpiration. This water vapor creates new clouds that travel farther inland to release their rain.

For many animals, however, sap-sucking pests such as aphids are a blessing. First, they benefit other insects such as ladybugs, whose larvae happily devour one aphid after another. Then there are forest ants, which love the honeydew the aphids excrete so much that they slurp it up right from the aphids’ backsides. To speed up the process, the ants stroke the aphids with their antennae, stimulating them to excrete the honeydew.

Walnuts have compounds in their leaves that deal so effectively with insects that garden lovers are often advised to put a bench under a canopy of walnuts if they want a comfortable

place to relax in the garden, because this is where they will have the least chance of being bitten by mosquitoes.

Above all, from dogs, which lift their legs at every available trunk. Their urine can burn bark and kill roots.

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.

There is a scientific observation that speaks to this: the blood pressure of forest visitors rises when they are under conifers, whereas it calms down and falls in stands of oaks.

and that’s why tree roots can breathe as well. If they didn’t, deciduous trees would die in winter when they discard their aboveground lungs. But the trees keep ticking over and their roots even grow a little, so energy must be produced with the help of the trees’ reserves, and for this the trees need oxygen. And that is why it is so awful for a tree if the soil around its trunk has been so compacted that the small air pockets in the soil have been crushed.

Chlorophyll, however, has one disadvantage. It has a so-called green gap, and because it cannot use this part of the color spectrum, it has to reflect it back unused.

The color is the result of a metabolic disorder.

For instance, water and nutrients—that is to say, “tree blood”—flow from the roots up to the leaves at the rate of a third of an inch per second.68

“Our leaders understand our well being is connected to the well being of our lands and waters… If we use our knowledge and our wisdom to look after [them], they will look after us into the future.”

Most national parks give in to the clamor of complaint and sell to sawmills the trees they have felled and removed from the forest to combat bark beetle infestations. This is a grave mistake. For the dead spruce and pines are midwives to the new deciduous forest. They store water in their dead trunks, which help cool the hot summer air to a bearable temperature. When they fall over, the impenetrable barricade of trunks acts as a natural fence through which no deer can pass. Protected in this way, the small oaks, bird cherries, and beeches can grow up unbrowsed. And when one day the dead conifers rot, they create valuable humus.

Katsuhiko Matsunaga, a marine chemist at the Hokkaido University, discovered that leaves falling into streams and rivers leach acids into the ocean that stimulate the growth of plankton, the first and most important building block in the food chain.