Peter Wohlleben's The Hidden Life of Trees: Astonishing revelation of how trees live and die
From how vegetarian animals influence tree growth to more, in his new book, 'The Hidden Life of Trees'. Peter Wohlleben not only challenges some traditional precepts of forestry, he also upends a few ecological principles
Trees count, recognise relatives, keep the stump of a dying friend alive for centuries, die of loneliness, identify the pest tormenting them, and have personalities. Is the author Peter Wohlleben the tree world's Erich von Däniken? It's not easy to dismiss his claims as almost each one in his The Hidden Life of Trees is backed by science.
Wohlleben tends an old beech forest in the Eifel mountains close to the German-Belgian border. Any forester will tell you that trees compete with each other for resources — sunlight, nutrients, and water. To achieve the best growth, foresters knock off stragglers so the others grow strong and fast.
Wohlleben says this is not always true. Community means everything to beech trees. Healthy ones feed their poorly off relatives through their roots to give them a boost. This is also the reason why trees in plantations are not as resilient as their wild relatives.
The author not only challenges some traditional precepts of forestry, he also upends a few ecological principles. Like this one. Vegetarian animals control plant growth. But the German forester says oaks and beeches limit numbers of herbivores. They may choose to go into a glut, producing so many nuts that herbivores can't possibly eat up everything. Fed by this reproductive exuberance, animal numbers explode. In other years, the trees may agree too many animals are a plague and produce fewer nuts. With no food to sustain them in the coming winter months, animals starve to death. This is as radical as suggesting that deer don't give birth in some years to limit the number of tigers. The food chain is not a one-way top-down process, and trees don't passively allow themselves to be eaten. They can seemingly outwit their predators.
When pests, be they insect or mammal, chew leaves, trees identify the species by their saliva and mount an appropriate defense. More recent research bears this out. German researchers found beeches and maples can tell if their branches and buds are accidentally twisted off by wind, or if they are deliberately chewed by deer.
Despite trees' ability to distinguish pests, they cannot react swiftly. In one minute, pain signals creep up a third of an inch. An inch of what? Trees don't have nerves. They have vessels to transport water and nutrients between root and crown. Do these signals travel up these channels? Wohlleben doesn't say.
Trees defend themselves either by producing toxic compounds that make leaves taste bitter or by summoning specific predators to gobble up their tormentors. They also set off alarm bells to give their neighbours the heads-up. How do they do it?
High school students learn of mycorrhizal fungi living in tree roots. The fungi's filigree tendrils burrow into soil in search of nitrogen and phosphorus among other nutrients. They trade these with their hosts for sugar. The bond between fungi and trees benefits both. But that's not all there is to the relationship.
In 1997, Suzanne Simard and colleagues from British Columbia, Canada, revealed these fungal strands are like fibre optic cables, now famously called the wood wide web, transmitting apprehensive signals from tree to tree. Beech trees use the same web to feed each other.
But acacia trees are quick to push the panic button. When giraffes browse on them, they release ethylene gas. Their neighbours 'smell' this alarm signal, possibly through slit-like breathing pores under the leaves. They churn out toxic compounds even before the giraffes approach them.
The ability of trees to sense their surroundings is astonishing. But how do they process these stimuli? Where is the brain, the seat of decision-taking, in a tree? In the most unlikely location: the roots. Hard as it is to imagine, root tips have brain-like structures says Wohlleben.
Where there is a brain, there must be a personality. Wohlleben uses the example of three oaks growing close together, sharing the same soil, weather, and nutrients. It's not far-fetched to expect all three to behave exactly the same. But yet when autumn arrives, one tree drops its leaves sooner than the others. In Wohlleben's interpretation, that tree is cautious, taking no chances. Its neighbours, however, boldly cling to their leaves despite the approaching chill. This individual difference shows trees have characters, says Wohlleben. This is far out and is not footnoted with any scientific study. Perhaps his conclusions will eventually be borne out by science. Or maybe an overlooked factor influences individual tree behaviour.
Each of the 36 chapters, an average of 6-7 pages long, deals with an aspect of tree physiology such as pollination, hibernation, and longevity. Wohlleben blends his observations with science with a dose of humour. His use of analogies — “Their thick trunks are like paunches attesting to an orgy of solar indulgence” — and facts (“a mature beech needs as much sugar and cellulose as there is in a 2.5 acre field of wheat”) make for an engrossing read, no small feat when the subject is as esoteric as the life of trees.
Scientists might bristle at the author's choice of words usually used to describe human and animal behaviour. He goes as far as comparing beech trees to a herd of elephants. By creating a warm fuzzy feeling, he succeeds in shifting readers' perception of trees. And he even makes a pitch for their welfare, saying it's all right to rear them for timber as long as their lives are made as comfortable as possible.
The narrative has a tiny cast of species — beech, oak, spruce, and fir. Elm, pine, willow, yew, and alders play minor supporting roles. Indian readers will learn a whole lot about Central European trees and zilch about our own tropical ones. The lack of similar ecological studies in India is glaring as Pradip Krishen, the author of Forest Trees of Central India, points out in an introduction to the subcontinent edition of Wohlleben's book. Krishen explores the mystery of why sal trees don't grow outside their range. Could they be similar in temperament to Californian redwoods? Do they need a community of relatives to thrive? One can only wonder because no one knows.
Until researchers fill this knowledge gap, Wohlleben's book is all we have.
The Hidden Life of Trees: What They Feel, How They Communicate by Peter Wohlleben
Published by Penguin Random House India; 2016; 319 pages
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