There are approximately three trillion trees in the world. That’s about 375 for every human being. To us, that number is almost inconceivable, although according to a 2015 Nature study it has fallen by about 46 per cent since the beginning of human civilisation, as we harvest wood for building materials and fuel. Even now, knowing everything we about how vital trees are for the survival of our planet and its wildlife, we continue to cull more than 15 billion a year.

It’s strange that humans would be so careless with Earth’s forests – not only because they help regulate the planet’s temperature and play host to complex ecosystems, but also because they’re so integral to much of human culture. From prehistory to the present day, trees have been regarded as spiritual hubs and places of worship, and they continue to hold symbolic significance in secular societies as well. Ancient yews guard our graveyards; giant oaks are tangled up in our national history; towering redwoods chart decades, centuries, and even millennia as the world changes around them.

In The Hidden Life of Trees, forester and author Peter Wohlleben lays out yet another reason for protecting our woodland – and, in particular, the last remaining patches of old-growth forest in Europe, which are continually under threat from industrial projects such as HS2. His argument? Trees’ thoughts, feelings, and communities run much deeper than we can imagine. Trees talk to each other via huge, hidden communications networks. Trees scream when they feel pain. Trees go out of their way to care for their young and their elders, just as humans do.

This sounds kind of familiar, right? Even if you didn’t don your 3D glasses and watch James Cameron’s Avatar on a mind-numbing IMAX screen in 2009, you’d no doubt recognise the Na’vi, a blue-skinned race of humanoid hunter-gatherers. This week, the director is taking them underwater in Avatar 2, a film that has been 13 years in the making – as a result, the aliens are plastered on every other billboard and bus stop. In the first film, though, they are forest-dwellers, populating giant, ancient trees on a distant moon named Pandora.

Besides being three metres tall and blue, the Na’vi differ from humans in one important way: they are in tune with the forest around them, bound by Eywa, a deity made up of all living things, which is particularly focused in the Tree of Voices. This is the crux of the film’s concept; humans from Earth, where all of the resources have been depleted, want to come in and slash the Na’vi’s home apart to mine a valuable mineral called unobtainium (inventive, I know). Thus begins an environmental parable that’s not unlike the Studio Ghibli epic Princess Mononoke, which came out 12 years before.

Avatar is a fantasy film, of course. We cannot, unfortunately, figure out if a tree feels pain by plugging our ponytails into a planet-wide neural network. Sadly, we also can’t pray to Eywa to unite all of Earth’s animals against rampant loggers and property developers. But… if Earth’s trees truly are joined in a mystical network, and possess an intelligence beyond our understanding, then maybe the ecological intelligence underpinning our reality isn’t so far away from the Na’vi’s as we think. Would that make us just as brutal and deranged as the film’s square-jawed villain, Colonel Quaritch?

Who better to turn to for answers than Peter Wohlleben himself? When I call him on Zoom, the Hidden Life of Trees author is freshly returned from wandering in the ancient beech forest he manages in Hümmel, Germany. A centuries-old clock heralds his arrival. Luckily, I discover when we get talking, he’s already an Avatar fan.

When did you first begin exploring the hidden life of trees, and why?

Peter Wohlleben: When I was a young child, about six, I wanted to become an environmentalist. It started more with animals than with trees. Then after school I was thinking about what to study and didn’t know what to do. First I thought I would like to study biology, then I found a newspaper report that the German forest commission was searching for students, and I thought okay, a forester is somewhat like a tree keeper. But it turned out that a forester is more like a tree butcher.

Then I thought about how to treat forests more gently. I read new scientific reports in the early 1990s [about how] trees are able to communicate, to care for each other, and things like that. As a forester, I was taught that the trees compete for light, for space, for water, and they are fighting against each other, which turned out to not be true.

Was there a specific moment that turned you away from ‘tree butchery’ – anything that’s lodged in your mind? 

Peter Wohlleben: There were several moments. One is that I felt so sorry for the old beech trees, called ‘mother trees’... as a forester, I was told to produce timber and to fell those old trees. For me, it was almost heartbreaking to see these old trees fall down. And so I changed this. And from this time on, I’ve never felled old trees again. They are still protected today, these areas.

The other thing is this very old stump. The tree had been felled 400 or 500 years ago, and this stump is still living even today. The only explanation that is proven so far, scientifically, is that old stumps like these are supported by surrounding trees, which keep them alive for centuries. Because this old stump needs sugar, and it’s not able to produce it itself anymore. So I realised – and that was 25 years ago or so – that trees support each other. They don’t fight each other. It’s a big community, a big family.

Some of the concepts you talk about sound like high fantasy. Can you explain what you mean, for example, when you say that trees talk to each other?

Peter Wohlleben: The term ‘language’, there is no universal definition for this. But what we always do is make definitions in a way that’s just good for humans, and worth nothing for other species. Tree language is different, it can be with smells, but there are hundreds of ‘words’ detected so far. There’s even communication not just among trees of one species, but also with animals. It’s newly detected that oaks, for example, are talking to birds when they are infested by caterpillars, so the birds come to help and eat those caterpillars, and the trees get rid of [them]. 

Then there’s communication in the underground, through root connections. Electrical and chemical signals are shared, for example, when trees are attacked by insects, or when they are suffering from drought, so the trees that are not yet suffering from the drought can reduce water consumption in advance. I would call what’s going on in the underground ‘tree-mails’, because it’s on electrical waves, like our emails. But it’s much slower because trees are, at minimum, 1000 times slower than we are. So it takes a long, long time to write a tree-mail, and to receive it even longer. Because trees are so slow, it’s so necessary for them to be aware of dangers a long time before things happen.

In The Hidden Life of Trees, you also talk about trees feeling pain, and even ‘screaming’ in some cases.

Peter Wohlleben: There’s strong evidence in conservative, conventional science. It’s nothing esoteric, and many people misunderstand that. You can prove it with hard facts. What we know is that, in certain situations, trees are producing pain-suppressing substances. The question is, are they really for suppressing pain? The truth is, you can sedate plants, sometimes even with the same chemicals as humans – because they have, in some cases, the same neurotransmitters that we have – and when they are sedated, they stop producing pain-suppressing substances. That’s exactly what we do, in similar situations. 

So we have strong hints for both the fact that plants feel pain and that they are conscious, because you have to be conscious to feel pain. I know many people would say, ‘Oh, no, that’s too much. What should we eat, if we don’t eat meat, and now we realise that plants can also feel pain?’ But it’s just a fact. I think the main [reason] why people have so many problems accepting that plants are not that far away from animals is that they think, ‘What will that mean for my everyday life?’ But the real question is, what is the main difference in the function between plants and animals? And most people can’t answer that. It’s photosynthesis, that plants can produce their own food, that’s the main difference. All other things, you can find in animals and plants as well.

Another example of intelligence in trees you give in the book is their ‘empathy’ – could you talk a bit more about signs of empathy in trees?

Peter Wohlleben: Again, there’s no clear definition for humans either. If we, as humans, support each other, we have the advantages of living in a big social community. If you support someone who’s sick, you get support when you are sick, and so on. So the question is, is there really support without condition? Perhaps this is the same with trees? To come back to the old stump, where is the advantage for healthy, intact trees to support this old stump? Perhaps the only thing, and that’s just a guess, is that this old stump has more knowledge. We know that trees can learn their whole life, and the older they get, the more knowledge they have stored. And they can share this; there’s evidence that young trees surrounding old trees behave like the old trees, so there is a transfer of knowledge. But we don’t know if this is really the reason why the strong trees support this old stump. Perhaps they feel just sorry for the old stump and support it like we support old and sick people.

“We have disturbed the cosmos so much that it’s not working properly anymore” – Peter Wohlleben

When you talk about trees as a community, or a family, how much of that is metaphor, and how much of it is you simply describing the world as you see it?

Peter Wohlleben: We know that mother trees are able to detect whether neighbouring trees are the same species. If they are family members, for example seedlings that belong to the mother tree, then you can see that these seedlings get more support than seedlings from other trees. Some plants are even able to see, via light, if the neighbouring plants belong to their family or not. That’s conservative science, from universities and well-known research institutions. So we see more and more that there are social structures among plants. It’s not a metaphor. 

We look at the world as we have since the Age of Enlightenment. That means that we look at other species as if they are just machines driven by genetic codes, acting automatically, and that we are the only ones for whom Mother Nature has invented special wonderful things. But we are a very young species on this planet, and we are on the shoulders of older species, which have developed all these wonderful things. So it would be very, very crazy if we would be the only ones with such social structures and social interaction. What we can imagine is that whales or wolves or other species are able to interact as we do, but to bring this understanding to trees… they are emotionally too far away [for us to be] able to understand or see what’s going on. Therefore it’s not a metaphor, it’s perhaps more a translation.

If we’re not so different to trees than we might think, then what are the ethical repercussions?

Peter Wohlleben: I think we should pay more respect to the needs of trees, or to plants in general. Our society has [worked] to pay respect to animals as much as they should, and now the next step is to pay it to plants, to pay it to the whole environment. 

We depend on all those wonderful creatures, especially on trees, because they are our best companions in fighting climate change, because they cool the air. That’s the most important reason that trees act together, because together they can change the local climate. It can cool down between 10 or 15 degrees celsius in summertime. Over a forest, you have significantly more rain clouds and significantly more rain, so they create their own local climate. They can do it, we can’t. So they are our best companions in fighting climate change. 

Also, such intact forests are communities of hundreds of thousands of species. It’s estimated by many scientists that about 90 per cent of all species in forests are undetected so far – most of them, of course, bacteria, fungi, and whatever. So it’s a wonderful cosmos, and we are able to protect this cosmos by not disturbing it. And that’s exactly what we see worldwide: we have disturbed this cosmos so much that it’s not working properly anymore. So just for our own sake, we should pay more respect to these wonderful creatures.

And we have much better companions in ancient forests than in new plantations?

Peter Wohlleben: Of course. Plantations are like animal factories, for trees. Trees are very much disabled, because when they are planted, their roots – and that’s the plant’s brain – are heavily damaged. We know that trees in such plantations are not interacting anymore, so it’s like a community of lone wolves. They are not able to produce much rain, they are not able to cool down. There is no artificial forest which is as good as a natural forest. We should first protect all remaining primaeval forest worldwide, and then secondly, let forests return. We can’t get forests back by planting trees.

Reading The Hidden Life of Trees, it can feel like forests have a better-functioning society than most humans. What do you think humans can learn about their own relationships from trees?

Peter Wohlleben: I would say, in general, that human society is not as bad as it seems to be when we look at some leaders. But we see it in trees also: some trees are not behaving as they should. Sometimes trees don’t connect to special individuals, and perhaps these are individuals which are not behaving well within this society. What we can learn from trees, and I think we see it in every human society as well, is that if you cooperate more and more individuals feel well. 

If it’s the law of the jungle – well, in reality the jungle is cooperative, but you know what I mean – then mankind wouldn’t last very long. Trees are instinctively working together, the bigger the community, the better. They are working on scales like whole continents together. That’s exactly what is good for humans as well.

I have some questions about Avatar, and the concept of Eywa – a worldwide neural network embodied in plants, animals, and particularly ancient trees. does this sound too far-fetched?

Peter Wohlleben: I think James Cameron has read the scientific papers very well, and implemented some things into his story which I think are very good. Yes, there is a network in the underground. We don’t know how far it reaches, but I’ll give one example: we know that oak trees and beech trees arrange together to bloom in one year – to produce a lot of acorns or seeds – and perhaps the next two, three, four years not [to bloom], to bring down the plant-eating mammal population. There is communication over hundreds of kilometres, which is proven. What we don’t know, so far, is how trees are doing this. 

To come back to your question, yeah, I think there is a big network of communication over hundreds, perhaps even thousands of kilometres. [The trees] are working together, and benefit from each other. Avatar, I think, is a wonderful story based on facts, or on things which might be very much possible.

“When you come to a traditional graveyard, the message is: this is a place of death. To come into a burial forest, the message is: it’s a place of life” – Peter Wohlleben

The film also explores the concept of a universal energy, which is ‘borrowed’ from nature and ‘returned’ upon death. As someone who runs a forest burial site, what do you think about that?

Peter Wohlleben: All our energy is borrowed, it’s sun energy. Sun energy, when it arrives on a dead planet, is wasted. But trees, or the whole environment, try to store this energy and to [transfer] this energy from one individual to the next. We are also benefiting from this stored plant energy. So the worst thing is to burn plants, for example in power plants, because plants are very good at storing energy.

At our individual end [in other words, when we die] we give this energy back to bacteria, to fungi, to other creatures. So the best thing would be to give the whole body completely back to the environment, but I think with eight billion people that would be a little problematic. So the second best thing is to be burned, and to bring the ashes back to the trees, and to protect the trees, because the ‘living headstone’ trees are better protected than in a national park or whatever.

Do you find that people are reassured by this concept of returning to the earth in your forest cemetery? Does it make the transition into death easier?

Peter Wohlleben: Of course, we experience this a lot. This idea, to be back in the cycle of life – that if one life ends, the next one starts – is best visualised in such a forest. When you come to a traditional graveyard, the message is: this is a place of death. To come into a burial forest, the message is: it’s a place of life. Life goes on, not individually, but we have to make space for the next individual. That’s just fair. It’s a completely different message, and for many people, it’s much easier to let family members go in such a place.

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