The Forest as a Social Network
Peter Wohlleben spent over twenty years working for the forestry commission in Germany before leaving to put his ideas of ecology into practice. He now runs an environmentally friendly woodland in Germany, where he is working for the return of primeval forests. He is the author of numerous books about trees.
In his new book, The Hidden Life of Trees: What They Feel, How They Communicate — Discoveries from a Secret World, now available in paperback, Peter convincingly makes the case for the forest as a social network. He draws on groundbreaking scientific discoveries to describe how trees are like human families: tree parents live together with their children, communicate with them, support them as they grow, share nutrients with those who are sick or struggling, and even warn each other of impending dangers. Wohlleben also shares his deep love of woods and forests, explaining the amazing processes of life, death, and regeneration he has observed in his woodland. After learning about the complex life of trees, a walk in the woods will never be the same again. Read an illustrated edited extract below.
The Hidden Life of Trees
When I began my professional career as a forester, I knew about as much about the hidden life of trees as a butcher knows about the emotional life of animals. The modern forestry industry produces lumber. That is to say, it fells trees and then plants new seedlings. If you read the professional literature, you quickly get the impression that the well-being of the forest is only of interest insofar as it is necessary for optimizing the lumber industry. That is enough for what foresters do day to day, and eventually it distorts the way they look at trees. Because it was my job to look at hundreds of trees every day — spruce, beeches, oaks, and pines—to assess their suitability for the lumber mill and their market value, my appreciation of trees was also restricted to this narrow point of view.
About twenty years ago, I began to organize survival training and log-cabin tours for tourists. Then I added a place in the forest where people can be buried as an alternative to traditional graveyards, and an ancient forest preserve. In conversations with the many visitors who came, my view of the forest changed once again. Visitors were enchanted by crooked, gnarled trees I would previously have dismissed because of their low commercial value. Walking with my visitors, I learned to pay attention to more than just the quality of the trees’ trunks. I began to notice bizarre root shapes, peculiar growth patterns, and mossy cushions on bark. My love of Nature—something I’ve had since I was six years old was reignited. Suddenly, I was aware of countless wonders I could hardly explain even to myself. At the same time, Aachen University (RWTH Aachen) began conducting regular scientific research programs in the forest I manage. During the course of this research, many questions were answered, but many more emerged.
Life as a forester became exciting once again. Every day in the forest was a day of discovery. This led me to unusual ways of managing the forest. 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. Machines have been banned from the forest for a couple of decades now, and if a few individual trees need to be harvested from time to time, the work is done with care by foresters using horses instead. A healthier— perhaps you could even say happier — forest is considerably more productive, and that means it is also more profitable.
I invite you to share with me the joy trees can bring us. And, who knows, perhaps on your next walk in the forest, you will discover for yourself wonders great and small.
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Gardeners often ask me if their trees are growing too close together. Won’t they deprive each other of light and water? This concern comes from the forestry industry. In commercial forests, trees are supposed to grow thick trunks and be harvest-ready as quickly as possible. And to do that, they need a lot of space and large, symmetrical, rounded crowns. In regular five-year cycles, any supposed competition is cut down so that the remaining trees are free to grow. Because these trees will never grow old they are destined for the sawmill when they are only about a hundred — the negative effects of this management practice are barely noticeable.
What negative effects? Doesn’t it sound logical that a tree will grow better if bothersome competitors are removed so that there’s plenty of sunlight available for its crown and plenty of water for its roots? And for trees belonging to different species that is indeed the case. They really do struggle with each other for local resources. But it’s different for trees of the same species.
It is obviously not in a forest’s best interest to lose its weaker members. If that were to happen, it would leave gaps that would disrupt the forest’s sensitive microclimate with its dim light and high humidity. If it weren’t for the gap issue, every tree could develop freely and lead its own life. I say 'could' because beeches, at least, seem to set a great deal of store by sharing resources.
Students at the Institute for Environmental Research at RWTH Aachen discovered something amazing about photosynthesis in undisturbed beech forests. Apparently, the trees synchronize their performance so that they are all equally successful. And that is not what one would expect. Each beech tree grows in a unique location, and conditions can vary greatly in just a few yards. The soil can be stony or loose. It can retain a great deal of water or almost no water. It can be full of nutrients or extremely barren. Accordingly, each tree experiences different growing conditions; therefore, each tree grows more quickly or more slowly and produces more or less sugar or wood, and thus you would expect every tree to be photosynthesizing at a different rate.
And that’s what makes the research results so astounding. The rate of photosynthesis is the same for all the trees. The trees, it seems, are equalizing differences between the strong and the weak. Whether they are thick or thin, all members of the same species are using light to produce the same amount of sugar per leaf. This equalization is taking place underground through the roots. There’s obviously a lively exchange going on down there. Whoever has an abundance of sugar hands some over; whoever is running short gets help. Once again, fungi are involved. Their enormous networks act as gigantic redistribution mechanisms. It’s a bit like the way social security systems operate to ensure individual members of society don’t fall too far behind.
In such a system, it is not possible for the trees to grow too close to each other. Quite the opposite. Huddling together is desirable and the trunks are often spaced no more than three feet apart. Because of this, the crowns remain small and cramped, and even many foresters believe this is not good for the trees. Therefore, the trees are spaced out through felling, meaning that supposedly excess trees are removed. However, colleagues from Lübeck in northern Germany have discovered that a beech forest is more productive when the trees are packed together. A clear annual increase in biomass, above all wood, is proof of the health of the forest throng.
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. Every tree now muddles along on its own, giving rise to great differences in productivity. Some individuals photosynthesize like mad until sugar positively bubbles along their trunk. As a result, they are fit and grow better, but they aren’t particularly long-lived. This is because a tree can be only as strong as the forest that surrounds it. And there are now a lot of losers in the forest. Weaker members, who would once have been supported by the stronger ones, suddenly fall behind. Whether the reason for their decline is their location and lack of nutrients, a passing malaise, or genetic makeup, they now fall prey to insects and fungi.
But isn’t that how evolution works? you ask. The survival of the fittest? Trees would just shake their heads — or rather their crowns. Their well-being depends on their community, and when the supposedly feeble trees disappear, the others lose as well. When that happens, the forest is no longer a single closed unit. Hot sun and swirling winds can now penetrate to the forest floor and disrupt the moist, cool climate. Even strong trees get sick a lot over the course of their lives. When this happens, they depend on their weaker neighbors for support. If they are no longer there, then all it takes is what would once have been a harmless insect attack to seal the fate even of giants.
'A chain is only as strong as its weakest link.' Trees could have come up with this old craftsperson’s saying. And because they know this intuitively, they do not hesitate to help each other out.
Trees: Aspen, Birch, Pine © Briana Garelli
Peter's Beech Grove © Peter Wohlleben