The Hidden Life of Trees is a book published in 2015 which discusses the lives of trees. It was written by Peter Wohlleben, who spent more than two decades working for the forestry commission in Germany. The Hidden Life of Trees is an enjoyable, informative, wondrous read, for it effectively communicates the details of an impressive organism.
In the foreword, the book begins by describing that trees have often been given human attributes by humans, and that this comes from a misunderstanding, for humans belong to a different branch of life than trees. Trees generally have lifespans much longer than humans, which means that they can take things at a much slower pace. That is, “One of the eldest trees on Earth, a spruce in Sweden, is more than 9,500 years old. That’s 115 times longer than the average human lifetime … The electrical impulses that pass through the roots of trees, for example, move at the slow rate of one third of an inch per second” (vii). It is then written that trees are social organisms, and that they do help each other, seen in how some trees would help a neighbor after it is felled by Homo Sapiens. It is described that trees communicate through their roots, making it similar to the internet in a way, and that they rely on cooperation to survive. Wohlleben talks about his experience with trees, and how the lumber industry is acting foolishly, as they are severely damaging tight-knit communities: “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” (xiv).
Wohlleben writes of a personal experience in which he saw the rotting stump of a tree that had been severed four to five centuries ago. He wrote that although the inside had decayed into humus, there was green underneath the bark. Because green is indicative for reserves of chlorophyll, he came to the conclusion that the surrounding trees were providing the dying tree with sugar to keep it alive. He then says that roots compose the social network of trees, and that they rely on each other to survive, for an isolated tree is very rare - it takes many trees to create a forest, and a forest is like an organism, though amplified. That is, “On its own, a tree cannot establish a consistent local climate. It is at the mercy of wind and weather. But together, many trees create an ecosystem that moderates extremes of heat and cold, stores a great deal of water, and generates a great deal of humidity … If every tree were looking out only for itself, then quite a few of them would never reach old age. Regular fatalities would result in many large gaps in the tree canopy, which would make it easier for storms to get inside the forest and uproot more trees. The heat of summer would reach the forest floor and dry it out. Every tree would suffer” (4). Trees, like many organisms, practice altruism, giving aid to others in case they may need it in the future. Wohlleben then writes that a tree’s canopy clearly demonstrates their cooperation, for most trees don’t savagely compete with others: “The trees don’t want to take anything away from each other, and so they develop sturdy branches only at the outer edges of their crowns … Such partners are often so tightly connected at the roots that sometimes they even die together” (5).
Wohllben then writes that while trees don’t talk in the sense that we humans are used to, they still communicate effectively by utilizing scent. The importance of scent is elaborated by Wohllben, who focuses on pheromones in humans - certain scents and sweats produced by a member of Homo Sapiens can attract potential mates. He then goes back to trees, writing that decades ago, scientists who were on the African savannah noted that umbrella thorn acacias were working together to repel giraffes from eating them: when the giraffes first began eating the leaves of an acacia, the tree began “pumping toxic substances into their leaves to rid themselves of the large herbivores” (7). The giraffes responded in turn, moving on to other trees. However, the trees they eventually ate were 100 yards away: the acacia tree being eaten had signalled to the others in its vicinity through the gas known as ethylene to also secrete chemicals to dissuade potential herbivores. Wohlleben writes that caterpillars can also trigger trees to release warning signals. However, as stated before, because trees live much longer, they take much more time to react to a threat. A situation which will cause a human to react in mere milliseconds will cause a tree an hour to act: “the plant signal travels at the slow speed of a third of an inch per minute. Accordingly, it takes an hour or so before defensive compounds reach the leaves to spoil the pest’s meal” (8). Trees have a pretty impressive defensive system, for they can detect the saliva of various species of insects: they are so good in detection at times that they “can release pheromones that summon specific beneficial predators … For example, elms and pines call on small parasitic wasps that lay their eggs inside leaf-eating caterpillars. As the wasp larvae develop, they devour the large caterpillars bit by bit from the inside out” (8). Wohlleben then continues, writing that while scent can disperse very quickly once they are released, they have a limit of 100 yards. Some trees, such as oaks, employ even more defenses, as they carry toxic tannins in their leaves and bark. When ingested, “These either kill chewing insects outright or at least affect the leaves’ taste to such an extent that instead of being deliciously crunchy, they become bioliously bitter. Willows produce the defensive compound salicylic acid, which works in much the same way” (9). Of course, trees don’t just rely on scent, for their root networks are also an effective means of communication. The roots of trees can reach twice as long as its crown, and the ground of a forest is densely packed with such roots, nicknamed “hyphae”: “One teaspoon of forest soil contains many miles of these ‘hyphae.’ Over centuries, a single fungus can cover many square miles and network an entire forest” (10). The health of a tree has a positive correlation with their ability to communicate with other trees, which is why those who have bad health are frequently targeted by insects. Trees which are bred in the modern lumber industry are largely isolated from others, and with no one to warn them of possible danger, they are constantly at risk of being exposed to risk factors. Wohlleben then writes that it is guessed at by some scientists that trees may communicate by moving their roots, for scientists discovered that the roots were “crackling quietly at a frequency of 220 hertz” (13).
Wohlleben writes that as his time as a forester, he had young trees girdled, that is, killed. To be specific, “In this process, a strip of bark 3 feet wide is removed all around the trunk to kill the tree … death comes slowly over a few years … However, many of the trees I girdled continued to grow with more or less vigor … Thanks to the underground network, neighbors took over the disrupted task of provisioning the rotos and thus made it possible for their buddies to survive. Some trees even managed to bridge the gap in their bark” (17-8). Wohlleben then writes of the reproductive system of trees, noting that they make copies of themselves through blooming. When they bloom, trees rely on the wind to scatter the pollen to get it to other trees. Because trees could potentially mate with themselves, to prevent the possibility of inbreeding, they consistently stay to one gender: “For example, there are both male and female willows, which means they can never mate with themselves but only procreate with other willows” (23). The reproductive cycles of trees greatly vary, for while some trees do the impressive task of releasing pollen once a year, others do it much less. Trees, despite being highly cooperative, do also compete to get more sunlight than the others through their growth of branches. The trees which blossom once a year are also putting themselves at a large risk, for they are focusing on the next generation and not on their own health. Consequently, their ability to fight off pests is greatly diminished. When seeds land on the ground, they, like the trees, vary in their lifespans. Some seeds wait a year before they start to grow, while other seedlings, like bird cherries, can wait for years before deciding to sprout. Despite all the pollen and seeds produced by trees, “Statistically speaking, each tree raises exactly one adult offspring to take its place. For those that don’t make it, seeds may germinate and young seedlings may vegetate for a few years, or even for a few decades, in the shadows, but sooner or later, they run out of steam … most give up and return to humus. Eventually, a few of the lucky ones that have been carried to open spaces on the forest floor by the wind or by animals get a good start in life and grow to adulthood” (29). Wohlleben then provides the audience with the following statistic: a beech tree produces at least thirty thousand beechnuts every five years, and, assuming it lives to an age of 400, it can go through sixty reproductive cycles, producing a grand total of 1.8 million beechnuts. From all of them, only one will grow into a complete tree: “in forest terms, that is a high rate of success, similar to winning the lottery. All the other hopeful embryos are either eaten by animals or broken down into humus by fungi or bacteria” (29).
Wohlleben then writes that trees that generally live a long time grow slowly when they are young. Some trees have to wait for a long time underneath the trees of their predecessors, seeing that much of the sunlight does not reach them. In human terms, trees under their elders have to wait for roughly half their lifetime to finally enjoy more sunshine: “The stunted trees can probably expect another two hundred years of twiddling their thumbs before it is finally their turn. The wait time is, however, made bearable. Their mothers are in contact with them through their root systems, and they pass along sugar and other nutrients” (34). Once the large, old trees are dead and subsequently collapse, the younger ones can compete with each other to reach the top first. Those who succeed usually get to enjoy the benefits for many years, while those who lose have to wait once again: “Overtaken by their comrades, they find themselves in the shadows once again. The difference is that it is even darker under the leaves of their cohort that has pulled ahead than it was under their mothers. The teenagers use up the greater part of what weak light remains; the stragglers give up the ghost and become humus once again” (35). A major threat to trees are honeysuckles that strangle them. If a young tree is ensnared by one and is covered in darkness, the honeysuckle will die, leaving it relatively unharmed, though with some scarring. If, on the other hand, it continuously gets exposed to the sunlight, the honeysuckle will continue to grow, and subsequently strangle the tree. Trees also value stability, for those which are unstable are easily knocked over during turbulent weather events, such as fierce winds and storms. Wohlleben writes that trunks are usually straight, the crowns act as a counterweight, and the roots help solidify the grip of the tree on the ground: “The roots must hold out under the onslaught so that the tree doesn’t topple over. To avoid this, the roots cling to the earth and to rocks. The redirected power of a windstorm can tear at the base of the trunk with a force equivalent to a weight of 220 tons. If there is a weak spot anywhere in the tree, it will crack. In the worst-case scenario, the trunk breaks off completely and the whole crown tumbles down. Evenly formed trees absorb the shock of buffeting forces, using their shape to direct and divide these forces evenly throughout its structure” (38).
Wohlleben writes that one of the biggest obstacles trees face is thirst, for they could easily satisfy their hunger due to them being autotrophs. He writes that “A mature beech tree can send more than 130 gallons of water a day coursing through its branches and leaves,” which means that such trees can easily deplete their area of water, which forces them to manage their resources effectively - to ensure a long, consistent lifespan, trees must be disciplined. During the winter season, many trees absorb more water than usual thanks to the snow and rain, and it could last them for months. Wohlleben then writes of the discipline of trees, writing that trees which suffer particularly fiercely from thirst are those which are usually in soil which usually have a lot of water, for they are strangers to the concept of water conservation, not to mention that they are unused to the sensation of deprivation. Trees which suffer from dehydration are likely to experience tears which may expose their insides to fungi and insects, which serves as behavior reinforcement and natural selection - “Nature is a strict teacher. If a tree does not pay attention and do what it’s told, it will suffer. Splits in its wood, in its bark, in its extremely sensitive cambium (the life-giving layer under the bark): it doesn’t get any worse than this for a tree. It has to react, and it does this not only be attempting to seal the wound … it will also do a better job of rationing water instead of pumping whatever is available out of the ground as soon as spring hits without giving a second thought to waste” (44-5). Scientists who conducted research on trees discovered that vibrations came from the trunk when the tree was suffering dehydration, which causes Wohlleben to believe that “when trees are really thirsty, they begin to scream. If you’re out in the forest, you won’t be able to hear them, because this all takes place at ultrasonic levels … When I think about the research results, in particular in conjunction with the crackling roots I mentioned earlier, it seems to me that these vibrations could indeed be much more than just vibrations-they could be cries of thirst. The trees might be screaming out a dire warning to their colleagues that water levels are running low” (48).
Wohlleben proceeds to discuss fungi, and that they are organisms that are a cross between animals and plants, for their cell walls are constructed of chitin, which is usually found in insects (and creates the exoskeleton of the lobster). Fungi also can’t photosythesize and attach themselves to other organisms to survive. Fungi commonly attach themselves to trees, and enter into a potentially symbiotic relationship: “The fungus not only penetrates and envelops the tree’s roots, but also allows its web to roam through the surrounding forest floor. In so doing, it extends the reach of the tree’s own roots as the web grows out toward other trees. Here, it connects with other trees’ fungal partners and roots. And so a network is created … it’s easy for the trees to exchange vital nutrients” (51). Fungi, however, exact a large cost, for they depend on the tree for food, and they can take up a full third of the tree’s nutrients. Fungi, besides providing the trees with communication, also filter out heavy metals and keep out intruders. They are very sensitive organisms, and due to pollution and climate change, they have become increasingly endangered, only illustrating even further the disastrous effects humans have and will continue to have on the organisms around them. Wohlleben then writes that an organism which is very important to trees such as spruce are woodpeckers, for trees are infested by beetles which may end their life and the trees around them. When the woodpecker sees the beetles, they are very efficient at getting them out, though they don’t care about the tree in the process - chips usually fly as the woodpecker does its business, and sometimes it makes its nest in the tree itself, which injures it further. Wohlleben then takes the mantle from the tree’s evolutionary perspective - even if the tree was to die from the woodpecker, at least its neighbors would be spared from a potentially fatal beetle infestation.
Wohlleben writes of how trees age, and he describes that what is skin to humans is bark for trees. Following this analogy, when bark is ripped off a tree, the tree feels a pain similar to what a human may feel if their skin was to be flayed. To deal with potential wounds, healthy trees annually add 0.5-1 inches to its girth. Trees also shed outer layers of bark, which ends up being protection for them. Wohlleben then writes that trees can be scarred for life if they are attacked by bark flies - “there are no wrinkles; instead, there are thousands of tiny pits and pustules that never disappear no matter how long the tree lives” (64). As the tree becomes old, the branches at the top may die and fall off due to them not being needed. Trees commonly die when fungi enter their system via small wounds, as the fungi proceeds to decompose the tree over decades. The tree responds by growing new wood, which stabilizes it for some time, until its trunk finally snaps, marking the end of its life. Wohlleben moves on to discuss that trees specialize according to which environment they are in. He cites that Central European trees “love nutrient-rich, loose, crumbly soil that is well aerated to a depth of many feet. The ground should be nice and moist, especially in summer … Snowfall should be moderate but sufficient that when the snow melts, it gives the soil a good soaking. Fall storms should be moderated by sheltering hills or mountain ridges, and the forest shouldn’t harbor too many fungi or insects that attack bark or wood” (74). Spruce deal with snow while having needles by methodically employing an extremely straight trunk and having branches that stuck out horizontally in the summer, so that when snow does come, the branches would support each other, making the tree seem thinner. A problem for trees with needles is that needles increase the surface area of the tree, making wind potentially more dangerous. Environments dangerous for most trees include areas with stagnant water (that are depleted of oxygen) and swampy ground.
Wohlleben then describes how little humanity knows of trees, writing that before the discovery of a spruce tree that was 9,550 years old (found by using carbon 14 dating), most people wouldn’t believe that spruce could live for more than five centuries. Wohlleben then states that most researchers don’t agree on how conscious plants are, which does make sense, considering that plants live and behave differently than animals. Wohlleben comes to describe the sheer importance of soil and its small inhabitants, writing that even though people are generally more passionate about large organisms than small ones, a forest which could house all those creatures would not exist to begin with if not for animals within the soil, which he nicknames “terrestrial plankton.” Such organisms include mites and weevils. Wohlleben then writes that when trees die, their nutrients go back to the environment, which shows how important they are to their respective environments, even in death: “The crumbling trunk is gradually gnawed and munched into smaller and smaller pieces and worked, by fractions of inches, more deeply into the soil. The rain takes care of whatever is left, as it flushes organic remnants down into the soil. The farther underground, the cooler it is. And as the temperature falls, life slows down, until it comes almost to a standstill. And so it is that carbon dioxide finds its final resting place in the form of humus, which continues to become even more concentrated as it ages” (94). Wohlleben then writes that today’s fossil fuels were the remains of trees which have perished 300 million years ago, and that the trees which later became fossil fuels were much larger (up to 100-foot-tall) than the trees of the modern age. He narrates the process of their remains becoming fossil fuels in detail: “Over the course of thousands of years, they turned into thick layers of peat that were then overlain with rocky debris, and pressure gradually turned the peat to coal” (94). Following this logic, Wohlleben writes that today barely any coal is being formed due to forests constantly being cleared and grossly manipulated by Homo Sapiens. Despite this, it is still possible to note the initial phases of coal formation by simply going into a forest and digging into the ground. The soil under the immediate ground is of a lighter color than the immediate surface, which shows that the dark soil has a concentration of carbon: “If the forest were left in peace from now on, this layer would be the precursor of coal, gas, or oil” (95). Wohlleben then writes that trees which are old are not, as many would expect, old and feeble. On the other hand, when researchers examined 700,000 trees on every continent, they discovered that the older the tree, the more rapid its growth. Wohlleben then states that if climate change policies are to be enacted (unlikely anytime soon due to partisan politics and short-term greed), trees should be allowed to grow old due to the previous observation.
Wohlleben acknowledges that even though many forests are located inland, they are still able to get water through their roots. He then writes that a major threat to trees are aphids/plant lice/greenflies which “attach their sucking mouthparts to the veins of leaves and needles. Thus positioned, they get royally drunk in a way no other animals can. The tree’s lifeblood rushes right through these tiny insects and comes out the other end in large droplets” (115). Caterpillars, unlike aphids, don’t drink the essential fluids of trees. On the contrary, they mainly eat leaves whole. Although they are small, they have the potential to reproduce rapidly. Bark beetles mount an aggressive, risky offensive. As Wohlleben writes, a single beetle approaches a tree and sees if it can get in. If it could, it would send an aromatic signal to other beetles to join in. If, however, it is killed by the tree’s response, no attack is mounted at all. Beetles want cambium, which is “the actively growing layer between the bark and the wood. This is where the trunk grows as wood cells form on the inside and bark cells form on the outside. The cambium is succulent and stuffed full of sugar and minerals … Cambium tastes like lightly resinous carrots, and it’s very nutritious” (119). If a beetle is successful at getting in a tree, it can stunt the tree’s response due to some of the fungi it carries. Consequently, “Because the fungi grow faster than the beetles drill, once they make it under the bark, they are always one step ahead. This means all the terrain the bark beetles encounter has been decontaminated and they can feed safely. Now there is nothing to stop a population explosion, and the thousands of larvae that hatch eventually weaken even healthy trees. Not many spruce can survive such massive attacks” (120). Honey fungus mushrooms and pinesap are also detrimental to trees, and some trees are killed when deer and other large animals use them for rubbing posts for extensive periods of time. However, if the diameter of the trunk is greater than 4 inches, the trees are generally safe from being maimed. Deer also frequently use trees for sustenance. If they consume too much, the tree can die from its injuries.
Trees, aside from being impressive organisms in their own right, also house many organisms, big and small. Big animals like woodpeckers generally like to live in healthy trees, so they take long stretches of time to create the homes they want, seeing that healthy trees are harder to burrow into than rotten or dead ones. Wohlleben then writes that each tree can house hundreds of organisms, and that “In total, a fifth of all animal and plant species-that’s about six thousand of the species we know about-depend on dead wood. As I have explained, dead wood is useful because its role as a nutrient recycler” (134). Trees do prepare for winter, though they don’t hibernate in the sense that many animals do - their leaves lose the luster brought to them by chlorophyll and eventually fall off to safeguard against storms. In some areas, during the winter there could be storms that have winds that are so strong that they can travel up to 60 miles per hour, which makes it imperative for the trees to rely on each other and to drop their leaves and needles to decrease their surface area. Wohlleben then writes that you can see the “personality” of a tree by going into a clearing in the forest - those trees which have begun to sprout new branches are the minority, the reckless ones, for growing new branches too quickly in the sunlight could make them vulnerable to fungi: “When you take your next walk into the forest, you can check for yourself to see that such behavior really is an individual choice and, therefore, a question of character … all have the same temptation to do something stupid like growing new branches on their trunks, but only a few give in. The rest keep their bark nice and smooth and avoid the predictable risk” (154). Wohlleben then writes of a tree’s potential injuries. He writes that when it comes to the initial reactions of trees in response to being attacked, “In deciduous trees, the vital topmost growth suddenly dies, leaving thick branch stubs with no side branches sticking up into the sky. The initial reaction of conifers is that their needles don’t last as long … In spruce you also get what is known in Germany as the ‘Lametta effect,’ where the twigs hang limply from the branches … A short time later, big flakes of bark break off the trunk. Things can deteriorate quite quickly from this point. Like a deflating hot air balloon, the crown implodes and sinks as it dies, and winter storms break off the dead branches. You can see this even more clearly with spruce, because the desiccated tips of dying trees contrast clearly with the living green of the lower branches” (157-8).
Wohlleben then writes that trees usually annually add a growth ring to the interior of their trunk, but that sick trees will refrain from doing so due to a lack of energy. Furthermore, when trees die, they often strike other trees on the way down. Most of the time, the damage done to other trees is minor, for only some branches break. Other times, however, the trunk is damaged, severely injuring the tree. What causes many trees to collapse are changes in density which are primarily done by injuries. Wohlleben then talks about honeysuckles yet again, and then he discusses mistletoes, which, instead of moving from the bottom to the top like honeysuckles, usually start from the top down: “To do this, they co-opt thrushes, who deposit the mistletoes’ sticky seeds when they clean off their beaks on the upper branches. But how do plants survive up there with no contact with the ground to get water or food? Now, way up in those lofty heights, there’s water and food aplenty-in the trees. To get at them, the mistletoes sink their roots into the branches they’re sitting on and simply suck out what they need. They are photosynthesizing for themselves, at least, so the host tree is ‘only’ short water and minerals. That’s why scientists call them ‘hemiparasites’ and not true parasites” (165-6). Wohlleben then writes of moss, stating that they are not as harmful as honeysuckle or mistletoe, for they don’t exploit the tree to a large degree, seeing how moss needs little water to survive. Lichen, unlike moss, appear higher up the tree, and they don’t harm the tree at all. They also take time to grow into “a moldy-looking coating over the bark, which prompts many visitors to my forest to ask whether the trees are sick. The trees are not sick: lichen doesn’t do them any harm, and the trees are probably completely indifferent to their presence” (168).
Wohlleben then writes that trees which are grown for decoration in urban areas are the equivalent of human street kids, for they are cut off from a community of other trees which can help them survive and grow. He writes that many efforts to create an aesthetically pleasing tree, such as severing the roots to make the tree easier to transport, are tantamount to grievous physical mutilation and torture for the recipient. Wohlebben then writes that while trees in urban areas are spoiled (seeing that they don’t have to wait in the shade, causing them to devour as much sunlight as they wish, not to mention their needs for water are consistently met by gardeners), they will suffer in the long-run due to a lack of self-discipline and prudence when it comes to resource management. These trees, tragically, live much shorter lives than ones which are unmutilated that live in conjunction with other trees in nature, which makes it important to take their wellbeing into account in future operations. Wohlleben describes that certain trees, like birch trees and quaking aspens, rely very little on other trees to survive, seeing that they generally burn themselves out by growing so quickly. In Wohlleben’s own words, these trees “rush through life, live beyond their means, and eventually wear themselves out” (183). Wohlleben then writes of how trees “travel” - although they are rooted into position and can’t move, their seedlings can be equipped with the proper anatomy (like fine hairs) to move away during reproductive seasons. The seeds also rely on other animals, such as mice, birds, and squirrels to get to other places: “The jay transports heavy seeds the farthest. It carries acorns and beechnuts a few miles away. The squirrel manages only a few hundred yards, whereas mice bury their supplies barely more than 30 feet from the tree” (187-8). Wohlleben tells the audience that trees have crossed the Alps millions of years ago, and that this was thanks to the fact that trees worked their way across the treacherous landscape over many consecutive years.
Wohlleben then writes of various events that can put trees in danger. For instance, tornadoes can deal a sizable amount of damage to a forest. Snow itself can apply a massive amount of pressure on a tree, causing it to crack. Also, floods are a major problem. Wohlleben writes that most fires that plague forests right now have been created by humans, which reflects how much damage mere carelessness can cause. Wohlleben then states that forests do indeed go through occasional fires, and that they are commonly necessary: dead material (like needles) need to be cleared in order to prevent them from negatively impacting organic creatures. Speaking from personal experience, when I once went to a national park for trees, the park ranger said that occasional fires are needed to maintain the health of the forest as a whole, for it is quite easy for the ground to be covered with layer upon layer of needles, leaves, and other material. Without fires, seeds that have dropped from trees would find the task of implanting themselves into the ground to be very difficult, for most areas would have been covered with the aforementioned materials. Therefore, a major mistake people make when it comes to fires is that they intentionally try to put them out, which only harms the forest’s health in the long run. As George Carlin once said, people should try not to meddle too much with nature. Clearly illustrated in this incidence, people start unnecessary fires that ravage forests while putting out much-needed ones that maintain cleanliness, clearly showing that we really understand very little of the world around us.
Wohlleben writes of the immigration of trees. While most trees don’t harm the environments they are planted in, sometimes they bring along unwanted guests, which is seen most often and most clearly in human activity, especially commerce which involves movement from one part of the globe to the other. For instance, the Asian long-horned beetle “probably traveled to Europe and other parts of the world from China in packing crates. The beetle is an inch long and has 2-inch-long antennae. To us, it’s a beautiful-looking beetle … Deciduous trees, however, find it decidedly less attractive, because it lays its eggs individually in numerous small splits in their bark. Voracious larvae hatch and feed, and adult beetles drill thumb-sized exit holes in the trunk. These holes are then attacked by fungi, and eventually the trunk breaks” (216). Then there’s ash dieback fungus, a mushroom which grows on fallen leaves, which is “well on its way to finishing off most of the ash trees in Europe” because it is highly infectious and lethal to trees (216). He then states that trees will probably continue to survive for a long time as a whole, for they are so widespread and geographically dispersed that it will take a truly catastrophic event to wipe them out for good (the Sixth Extinction?). Wohlleben then writes of the clean air of forests, writing that “Forest Air is the epitome of healthy air,” for trees filter out toxins and negative material from the air - “Coniferous forests noticeably reduce the number of germs in the air, which feels particularly good to people who suffer from allergies” (221-2). Furthermore, the particles which are filtered by trees in forests include “not only pollutants such as soot but also pollen and dust blown up from the ground. It is the filtered particles from human activity, however, that are particularly harmful. Acids, toxic hydrocarbons, and nitrogen compounds accumulate in the trees like fat in the filter of an exhaust fan above a kitchen stove” (221-2). Wohlleben then states that most people who go through forests do report better health, and that every square mile of forest sees trees releasing 29 tons of oxygen. A person needs 2 pounds of oxygen a day to survive - mathematically speaking, a square mile of forest can provide air for ten thousand people.
Wohlleben writes that trees “breathe” via their needles, leaves, and roots. Trees inhale carbon dioxide and exhale oxygen, which makes them great company for animals, including Homo Sapiens, for we do the opposite. Wohlleben then states that recent scientific notions support the conclusion that trees need to sleep (or at least rest), and that they could suffer from sleep deprivation, for they are unable to constantly photosynthesize. In Wohlleben’s own words, “In 1981, the German journal Gartenamt reported that 4 percent of oak deaths in one American city happened because the trees were subjected to light every night” (226). To specify, trees register whether it’s night or day via the temperature, seeing how in another scenario, when forest fans brought “young oaks and beeches into their houses … where they kept them in pots on windowsills,” the trees couldn’t relax or rest due to the fact that “In cozy living rooms there’s no such thing as winter as far as the temperature is concerned,” which caused them to die from sleep deprivation (226). Wohlleben then writes that humans, in the current age, commonly want to leave for nature. This is seen very well in the establishment of national parks and the general consensus of German politicians to leave 5 percent of forest untouched at the time the book was written. Wohlleben states that trees should be conserved by being left alone - meddling on the part of Homo Sapiens will likely end in trouble, seen in how many trees in plantations commonly collapsed from 60-mile-per-hour winds, while that is much, much rarer in the wild. Wohlleben writes that he doesn’t know “of a single case where an old deciduous forest left to its own devices for many years has suffered comparable damage in similar weather. And so all I can say is: let’s have a bolder approach to wilderness!” (240).
Wohlleben then writes that humans have been carelessly and needlessly brutal with animals and organisms in the past, and that as society becomes more prosperous, people are seeking to decrease the amount of suffering they are linked to. This is seen especially well with veganism and vegetarianism. For example, in 1990 Germany passed a law, TierVerbG, that gave animals more rights (humans are animals too, of course). In Switzerland, the mention of trees and the protection of organic life is explicitly written in the constitution. Wohlleben then writes that even though humans do consume a large amount of organisms and therefore cause a significant degree of suffering, we could certainly cut back on some behaviors, such as burning wood in fireplaces (you’re burning the corpse of a tree that could have helped its surroundings). He ends with the following paragraph: “But we shouldn’t be concerned about trees purely for material reasons, we should also care about them because of the little puzzles and wonders they present us with … perhaps one day the language of trees will eventually be deciphered, giving us the raw material for further amazing stories. Until then, when you take your next walk in the forest, give free rein to your imagination-in many cases, what you imagine is not so far removed from reality, after all!” (245).
Personal thoughts:
The Hidden Life of Trees by Peter Wohlleben is a fantastic, informative, inspiring read, for it clearly presents the mighty organism that is the tree. Wohlleben accurately describes the anatomy and biology of trees, and many of the facts that he presents are sure to change your overall view of the world. I highly recommend The Hidden Life of Trees to anyone interested in biology, trees, and science.
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