Why are trees so important?

I'm walking in the Eifel Mountains in western Germany, through cathedral-like groves of oak and beech, and there’s a strange unmoored feeling of entering a fairy tale. The trees have become vibrantly alive and charged with wonder. They’re communicating with one another, for starters. They’re involved in tremendous struggles and death-defying dramas. To reach enormousness, they depend on a complicated web of relationships, alliances and kinship networks. Wise old mother trees feed their saplings with liquid sugar and warn the neighbors when danger approaches. Reckless youngsters take foolhardy risks with leaf-shedding, light-chasing, and excessive drinking, and usually pay with their lives. Crown princes wait for the old monarchs to fall, so they can take their place in the full glory of sunlight. It’s all happening in the ultra-slow motion that is tree time so that what we see is a freeze-frame of the action. My guide here is a kind of tree whisperer. Peter Wohlleben, a German forester, and an author has a rare understanding of the inner life of trees and is able to describe it inaccessible, evocative language. He stands very tall and straight, like the trees he most admires, and on this cold, clear morning, the blue of his eyes precisely matches the blue of the sky. Wohlleben has devoted his life to the study and care of trees. He manages this forest as a nature reserve, and lives with his wife, Miriam, in a rustic cabin near the remote village of Hümmel. A revolution has been taking place in the scientific understanding of trees, and Wohlleben is the first writer to convey its amazements to a general audience. The latest scientific studies, conducted at well-respected universities in Germany and around the world, confirm what he has long suspected from close observation in this forest: Trees are far more alert, social, sophisticated—and even intelligent—than we thought. With his big green boots crunching through fresh snow, and a dewdrop catching sunlight on the tip of his long nose, Wohlleben takes me to two massive beech trees growing next to each other. He points up at their skeletal winter crowns, which appear careful not to encroach into each other’s space. "These two are old friends," he says. "They are very considerate in sharing the sunlight, and their root systems are closely connected. In cases like this, when one dies, the other usually dies soon afterward, because they are dependent on each other." Since Darwin, we have generally thought of trees as striving, disconnected loners, competing for water, nutrients, and sunlight, with the winners shading out the losers and sucking them dry. The timber industry, in particular, sees forests as wood-producing systems and battlegrounds for the survival of the fittest. There is now a substantial body of scientific evidence that refutes that idea. It shows instead that trees of the same species are communal, and will often form alliances with trees of other species. Forest trees have evolved to live in cooperative, interdependent relationships, maintained by communication and a collective intelligence similar to an insect colony. These soaring columns of living wood draw the eye upward to their outspreading crowns, but the real action is taking place underground, just a few inches below our feet. "Some are calling it the ‘wood-wide web,’" says Wohlleben in German-accented English. "All the trees here, and in every forest that is not too damaged, are connected to each other through underground fungal networks. Trees share water and nutrients through the networks and also use them to communicate. They send distress signals about drought and disease, for example, or insect attacks and other trees alter their behavior when they receive these messages." Scientists call these mycorrhizal networks. The fine, hairlike root tips of trees join together with microscopic fungal filaments to form the basic links of the network, which appears to operate as a symbiotic relationship between trees and fungi, or perhaps an economic exchange. As a kind of fee for services, the fungi consume about 30 percent of the sugar that trees photosynthesize from sunlight. The sugar is what fuels the fungi, as they scavenge the soil for nitrogen, phosphorus, and other mineral nutrients, which are then absorbed and consumed by the trees. For young saplings in a deeply shaded part of the forest, the network is literally a lifeline. Lacking the sunlight to photosynthesize, they survive because big trees, including their parents, pump sugar into their roots through the network. Wohlleben likes to say that mother trees "suckle their young,’’ which both stretches a metaphor and gets the point across vividly. Once, he came across a gigantic beech stump in this forest, four or five feet across. The tree was felled 400 or 500 years ago, but scraping away the surface with his penknife, Wohlleben found something astonishing: the stump was still green with chlorophyll. There was only one explanation. The surrounding beaches were keeping it alive, by pumping sugar to it through the network. "When beeches do this, they remind me of elephants," he says. "They are reluctant to abandon their dead, especially when it’s a big, old, revered matriarch." To communicate through the network, trees send chemical, hormonal and slow-pulsing electrical signals, which scientists are just beginning to decipher. Edward Farmer at the University of Lausanne in Switzerland has been studying the electrical pulses, and he has identified a voltage-based signaling system that appears strikingly similar to animal nervous systems (although he does not suggest that plants have neurons or brains). Alarm and distress appear to be the main topics of tree conversation, although Wohlleben wonders if that’s all they talk about. "What do trees say when there is no danger and they feel content? This I would love to know." Monica Gagliano at the University of Western Australia has gathered evidence that some plants may also emit and detect sounds, and in particular, a crackling noise in the roots at a frequency of 220 hertz, inaudible to humans. Trees also communicate through the air, using pheromones and other scent signals. Wohlleben’s favorite example occurs on the hot, dusty savannas of sub-Saharan Africa, where the wide-crowned umbrella thorn acacia is the emblematic tree. When a giraffe starts chewing acacia leaves, the tree notices the injury and emits a distress signal in the form of ethylene gas. Upon detecting this gas, neighboring acacias start pumping tannins into their leaves. In large enough quantities these compounds can sicken or even kill large herbivores.

I'm Jennifer Lawrance. From London, United Kingdom. I'm a freelance article writer.