Family Trees, Forests and The Intelligent Green Network Under Our Feet

It’s difficult to escape from a World where everything is connected.  To spend time in Nature, to find quiet and rest from our unbalanced existences inside our man-made concrete jungles.  To seek wisdom in the forest.  But we don’t understand Nature.  We think: If only those trees could talk!

Three Trillion Trees

A photograph of a busy pedestrian crossing at a city road junction. From "Intelligent Trees" Screenshot: NaturPhilosophie
A man-made connected network.

Little do we realize that underneath a world of stillness and peace, information is rushing back and forth inside a connected network of roots and fungi.

The Coastal Pacific Rainforest of North America is famous all over the World for its ancient giants.  Trees of heights around 100 metres and over 1,000 years of age.

People can walk and wonder about these amazing trees growing across the centuries.  But no longer are these places only described by mythological metaphors.  For we live in an age of Science.

Trees and Kins at a Microscopic Level

Scientists are beginning to understand the importance of forests as they uncover more details about the relationships between trees on a microscopic scale.

At the University of British Columbia in Vancouver, Canada, Dr. Suzanne Simard, Professor of Forest Ecology, conducts ground-breaking research.  Together with a team of dedicated forestry scientists, she wants to find out more about the methods of communication amongst trees:

Before I became a professor, I was actually a forester. […]  As I started working for the forest industry, I started to realize that what was happening didn’t really mesh very well with what I understood forests to work like.

What the forest industry was doing then was planting one or two species in clear cuts.  This was very different than what I understood forests to grow like, where there are mixes of species.

Managing the Forests

Northwest Coastal Map: Coastal temperate rainforests, among the rarest ecosystems on Earth as well as being the most carbon dense, stretch along the Pacific Coast from northern California to the Alaska panhandle. Map (left) by Dominick DellaSala and Island Press / photo (right) by John Schoen.

Pristine forests are rather unique places on Earth.

When we go walking into the woods, we expect to find Nature untouched and pure.  What we experience is very different.

Forests have been intensively managed for centuries.

We wander through an environment that has been largely shaped by people.

What happened was that they ended up using the same species everywhere.  The standard practice was to clear-cut and then plant either Pine or Fir or Spruce.  One species.  And I thought, what was going on here?  The community was not intact any more.

Dr. Suzanne Simard, Professor of Forest Ecology, University of British Columbia, Canada


An old-growth stump remains in an old clearcut in the Caycuse watershed, British Cloumbia, Canada. Photo: Jesse Winter / The Narwhal

The problem with clearcutting of trees started with the beginning of logging in late 19th Century Canada.  The aim was to harvest timber in the most economical way possible.

At the time, reforestation, aesthetics and habitat conservation of fish and wildlife were simply not considerations.

Clear-cutting removes trees from an area of one hectare or more, and greater than two tree heights in width, in a single harvesting operation.  A new even-aged stand is then obtained by planting natural or advanced regeneration, or direct seeding.

The opening size and dimensions created are generally large enough to limit significant microclimatic influence from the surrounding stand.

Although a broadly accepted practice in the forest industry, opponents of clear-cutting suggest it should never be done because:

    • Old growth forests are healthy ecosystems that have evolved over centuries to be more resistant to insects and disease.
    • Clear-cutting inhibits the sustainability of healthy forest ecosystems.
    • It increases soil erosion, as well as water degradation and silting in creeks, rivers, and reservoirs.
    • It can result in deforestation.
    • Aesthetics and forest views are compromised.

Since 2000, the annual rate of deforestation in British Columbia has been approximately 6,200 hectares per year.

British Columbia’s rarest forest ecosystems are rapidly disappearing and if the province doesn’t act immediately to defer logging in key areas, as recommended by the 2020 Old Growth Strategic Review, they will be lost forever.

Lonely Trees Do Not Thrive

A famed, solitary old-growth Douglas fir named Lonely Doug stands in a clear cut not far from the Fairy Creek and Caycuse watersheds, British Columbia, Canada. Photo: Jesse Winter / The Narwhal

The forestry scientists started to examine why trees didn’t seem to grow well when they were by themselves.

They found out that when you remove certain species from their neighbours that these trees actually became ill.  They became diseased and at greater risk of insect attack.

Thinking that part of the solution must lay below the ground, they decided to take a closer look.

A diagram showing the basic anatomy of a tree, including the crown of foliage, the trunk and the underground root system.The Trees

What we call a tree is only what is visible above ground.  We consider a tree to consist of a trunk and crown.  However, the major part of its life takes place underground.  A lot more happens in the forest than at first meets the eye.

The Roots

The root system of a tree can extend as far as 2-4 times the diameter of its crown.  Only scientists with state-of-the-art research techniques are able to dig deep enough into this matter to uncover that these roots are more than water pipes.

I started looking at the root systems and I found that the roots of these different species when they grew together, Birch and Fir an Cedar and Hemlock, were all intertwined and linked together.  I learned later on through more research that these root systems actually formed what is called a Mycorrhizal Fungal Association.

Dr. Suzanne Simard, Professor of Forest Ecology, University of British Columbia, Canada

The Mycorrhizal Fungal Associations

Typical appearance of ectomycorrhizal roots of trees – the short, nutrient-absorbing lateral roots lack root hairs but are covered by a multilayered sheath of fungus (light-coloured). Image: Archive Bio Ed

Mycorrhizal fungi are a certain species of fungi which associate with all of the tree species worldwide.  They form a symbiotic relationship where the fungus grows into the roots and provides the tree with nutrients and water gathered from the soil.

Mushrooms are only the fruiting bodies of fungi, just as apples are the fruit of apple trees.  Fungi are very underestimated organisms because most of us appreciate only the fruit.

Fungi can spread over several square kilometres.  One teaspoon of soil may contain several kilometres of threadlike hyphae that form the mycelium of the fungus.

For their services, they charge sugar and other products of tree photosynthesis.

The tree shares up to a third of its total production with the fungi.

How does this actually affect the way trees are growing?

We found, when we mapped these forests, that all of the trees were linked together in a single massive network.  So then I thought OK if they are all linked below ground, then what are these linkages about?

Dr. Suzanne Simard, Professor of Forest Ecology, University of British Columbia, Canada

Networking Opportunities

Once they knew those links were present, the team carried out more sophisticated experiments.

Mycorrhizal fungi in temperate forests allow the exchange of carbon among trees. Source: New Zealand Geographics

They labelled one tree with an isotope and traced it to its neighbour.  They found that carbon molecules were moving from one tree to another through these mycorrhizal networks.

Then they thought that if carbon was involved, maybe other molecules were involved too.  They started labelling trees with nitrogen, phosphorus and deuterated water.

All these elements were found to move back and forth between the trees.

This started to provide a rudimentary understanding of the language of trees.

Birch trees will be linked to other Birch trees, but also to the Douglas Fir and the Hemlock. […]  The mycorrhizal network is just below the surface of the forest floor.

Dr. Suzanne Simard, Professor of Forest Ecology, University of British Columbia, Canada

As you walk on the forest floor, you are only centimetres or millimetres away of the top of this network.  The network below ground can be visualized as a market place, where the food is either offered or received by all the trees that are linked together.

But what about the competition?

Trees of One Species Are Not Competitors

If all trees are eating at the same table, then why do they not steal from each other and suck each other dry, in a struggle for the survival of the fittest?

Trees of one species are not competitors.  On the contrary, they actually support each other almost unconditionally.  The weak are supported by the strong.  Only together they can, for example, regulate the micro-climate and lower the air temperature because trees like it cool and moist.

Peter Wohlleben, Forest Ranger, West Germany, Author of ‘The Hidden Life of Trees’

Here, the individual tree is not as important as its community.

Trees care for each other.  We can think of that as an interaction between trees, but really they are looking after each other.

Trees Are Not Loners

When we mistake trees for loners, each of them growing by themselves, oblivious to their neighbours and the environment, we underestimate them by far.

If forests are actually not the kind of harsh environment we expect them to be, where competition determines the survival of the strongest, fastest and toughest, then maybe a closer look might reveal even further relationships that surpass our expectations.

The forest industry wants trees to grow quickly.

Initially, trees do grow quite fast, when they grow by themselves.  However, that is not what they prefer.

Normally, trees would rather stand closely together.  They love company and taking things slow.  Trees do not need to be separated from alleged competitors.  On the contrary, we need to allow them to live in tight groups as they like to do.

Friendship Among Trees

Oak and Beech Forever in Mark Ash Wood, New Forest, United Kingdom  Image : Pinterest

There is actually friendship among trees.  It doesn’t happen very often because tree seedlings cannot choose whom they will be growing next to for the rest of their lives.

Maybe 1 out of 50 trees will befriend its neighbour.

But they grow their branches away from each other, so that they don’t interfere.  Their roots intertwine intensively.

It’s like an old couple.  If one of them dies, the one left behind might suffer, and die soon after.

For a tree, it is a disaster when the social network collapses.

Where trees have blown over in a storm, any remaining tree is now left by itself and gets sick.  The tips of its branches die back.  The leaves turn earlier in the fall, so it cannot photosynthesize properly.  It really suffers.  If it is not able to reconnect with other trees, it will likely die as well.

Do trees have a sense of friendship?  It’s language that we are using here to describe how trees relate to each other.  In Ecology, we call those things: interactions.

Dr. Suzanne Simard, Professor of Forest Ecology, University of British Columbia, Canada

Interaction is a very clinical term.  When we think about interactions, we think of:

    • Do they help each other?
    • Do they compete against one another?
    • Is one a parasite or a pathogen?

Species interact in a myriad of ways.  Some of them are beneficial. Science calls this facilitation.  In human relations, we call that friendship.

It’s just a matter of language.  When I think back to my early work with plantations and we were planting single species of trees and weeding out the species we didn’t want, I found that Douglas Fir would suffer, when we took Birch away from it.  We were affecting that facilitation between them.

So, is there friendship in forests?  Sure there is friendship in forests.  There are mutualistic facilitative relationships going on all the time.

Dr. Suzanne Simard, Professor of Forest Ecology, University of British Columbia, Canada

The transfer of carbon back and forth, the nutrition that the Birch provided for the Fir, the resistance against the pathogens in the soil. When the Birch was taken away, the Douglas Fir lost its friend, its facilitator.

Connected trees may form bonds of friendship, but they also link each tree to all of the others over hubs, very similar to our computer networks.  This is in a way the ‘Internet of the Forest’.

The Wood Wide Web

Sixty-seven Douglas fir trees of various ages were found to be intricately connected below ground by ectomychorrhiza from the Rhizopogon genus. Rhizopogon, which means ‘root beard’ in Greek, is commonly found living in a symbiotic relationship with pine and fir trees, and thus is thought to play an important ecological role in coniferous forests. Areas occupied and trees connected by Rhizopogon vesiculosus are shaded blue, or shown with blue lines, while Rhizopogon vinicolor colonies and connections between trees are coloured pink, or shown by pink lines. The most highly connected tree was linked to 47 other trees through eight colonies of R. vesiculosus and three of R. vinicolor. Source: NewZealandGeographics

Scientists who try to visualize these connections have been creating complex models that look like a map.  A map of the ‘Wood Wide Web’.

We were also able to identify which trees were the most important part of the network.  Which ones were the most highly linked.  We found that the biggest, oldest trees were the most highly linked.  We ended up calling these the Mother Trees, because we discovered through this map that the younger trees were growing up by hooking into the network and growing up around these Mother Trees.

Dr. Suzanne Simard, Professor of Forest Ecology, University of British Columbia, Canada

Trees are very social beings.  The parents, the mother trees, are looking after their offspring.  Their roots grow together and they feed them a sugar solution.

One could say that the Mother Tree suckles their offspring.

Peter Wohlleben, Forest Ranger, West Germany, Author of ‘The Hidden Life of Trees’

Growth Rate and Relatedness

To some it may seem strange to compare the flow of nutrients between older trees and their kin with human relationships.

Analogies like that, based on the observations of a practitioner should stand on a solid ground of scientific facts.

At UBC, students at the Faculty of Forestry conduct basic research about those relationships between Mother Trees and their kin.

All their experiments involved both field and greenhouse environments.  Similar techniques were used in both to compare it the other one.

We go into a Douglas Fir forest to gather soil.  That soil has a mixture of mycorrhizal fungi that prefer to associate with Douglas Fir.  We use that mixture to inoculate our trees.

Dr Monika A. Gorzelak, Forest and Conservation Sciences, UBC

They grew ‘Mother Trees’.  Basically, these were potted seedlings, inside mesh-bags.  These mesh-bags would either allow the mycorrhizal network to form with the neighbouring seedling, or not.

  We use mesh-bag to keep the roots from going through and touching each other and transferring between roots.  We want just the fungi to meet in the middle.

Dr Monika A. Gorzelak, Forest and Conservation Sciences, UBC

Over a period of a few months, they allowed these two seedlings, the ‘Mother Tree’ and her kin, or the ‘Mother Tree’ and the stranger, to communicate with each other through this mycorrhizal network that had formed.

We had to be able to do the experiment in the greenhouse, so we couldn’t bring in a big old ‘Mother Tree’ and plant her in a plot.  We had to use seedlings, because of the restrictive environment of a greenhouse.

Dr. Suzanne Simard, Professor of Forest Ecology, University of British Columbia, Canada

The idea was that the tree seedling that grew up first was well established and had more nutrients to spare than the one planted later.

So the one that was previously established had more resources than it needed.  It was able to shuttle some of those resources to its little brother growing up next to it.

Dr Amanda  Asay, Forest and Conservation Sciences, UBC

The term ‘Mother Tree’ is a term that resonates with people, because our culture understand the importance of mothers in families.  But it’s probably not the most scientifically accurate term.

What scientists are really talking about is relatedness.

Whether Mother Trees are related to trees around her or new trees that are coming up in her neighbourhood, it’s really about whether their genetics are well related to each other or not.  Whether they are distant or close together.

Dr. Suzanne Simard, Professor of Forest Ecology, University of British Columbia, Canada

One of the differential responses was when the newer seedling, was related to the older seedling.

The big seedling actually slowed down its growth rate.

And it appeared to make room for its younger sibling to grow.

Carbon and Nutrients

The tree seedlings are labelled with C13 isotopes and left to photosynthesize in the greenhouse.

The scientists labelled these mother trees with Carbon-13, which is an isotope they injected into a plastic bag around the seedling.

That bag completely sealed in the air around the tree seedling.

Then they allowed the seedling to photosynthesize with 13CO2.

Any sugars, any products it made was labelled.

We then look for that 13C in the recipient plants.  Remember the recipients are kin or stranger.  So, we look at the ratio of the amount of carbon that is present.

Dr Monika A. Gorzelak, Forest and Conservation Sciences, UBC

A photograph showing a female forestry scientist looking through a microscope at UBC greenhouse. From "Intelligent Trees" Screenshot: NaturPhilosophieAfter a while, the roots were clipped and washed, then morphotyped using a microscope.

What the scientists are studying are the fungal connections on the root tips.

At this point, the roots were ready to be dried in a large oven, then each portion was frozen separately using liquid nitrogen.

The root samples were then ground into a powder that was weighed carefully in very small increments.  This powder was eventually analyzed in the laboratory using micro-spectroscopy to determine how much 13C was in the sample.

And we found out that seedlings that were kin seedlings were receiving more carbon from Mother Trees than strangers were.  Then it starts to look like a family.

Dr. Suzanne Simard, Professor of Forest Ecology, University of British Columbia, Canada

The Mother Tree is effectively nurturing her own family.  But she is also looking after her whole neighbourhood.

So it’s not just a family.  It’s a whole community of trees.  Each with their own role to play in the forest.

Dr. Suzanne Simard, Professor of Forest Ecology, University of British Columbia, Canada

Mother trees who care lovingly for their children and their neighbours?

Information Flow

We discovered that the Mother Tree was affecting how those seedlings grew.  So if we changed the linkages or we removed them, those seedlings would behave differently.  They would either grow worse or they would grow better.

Dr. Suzanne Simard, Professor of Forest Ecology, University of British Columbia, Canada

What the forestry conservation scientists were gathering from all this data was:

If the Mother Tree was trying to make a favourable place for her seedlings, then she would encourage their growth and send more nutrients to those seedlings and they would grow better.

But if the Mother Tree ‘knew’ that the environment around her was not very hospitable for her young, if there were diseases or insects around, she would make it more difficult for the seedlings to grow.

She would be antagonistic towards them or become more competitive.  This said to me that the Mother Tree was communicating with her young, in order to favour the survival of those seedlings, whether they should be further away or close to her depending on how favourable the environment was.

Dr. Suzanne Simard, Professor of Forest Ecology, University of British Columbia, Canada

The experiments are also carried out in the forest.  The scientists go to big old Mother Trees and grow seedlings that are related or distantly related to her, and they study how they perform.

They compare the results they obtained in the greenhouse with what actually happens in the forest.

Do Trees Know Fear or Pain?

Trees are studied, measured, cultivated or cut.  They seem defenceless because they cannot run away from danger.

But some plants have developed amazing skills to react to attacks.

Mimosa pudica reacts by folding its leaves when touched or exposed to heat.  The foliage closes during darkness and reopens in light.  Its unique response makes it ideal for many experiments regarding plant habituation and memory.

Even plants don’t like to get hurt.

Trees have feelings.  They can feel pain.  But can also have emotions such as fear.  This is apparent for example in this Oak. It grows these clusters of twigs.  Signs of great distress.  But the Oak will behave differently if, for example, attacked by insects that bore into its bark.  It would feel pain.  Electrical signals would run through its fiber and the Oak would accumulate defence substances.  At the same time, it will alarm its colleagues via root networks and fungi.  So that they could get ready to accumulate defence substances even though they haven’t been attacked yet.  Once the insects arrive, the other Oaks will be prepared.

Peter Wohlleben, Forest Ranger, West Germany, Author of ‘The Hidden Life of Trees’

A forest is much healthier and more resistant when individual trees warn the rest of their community as soon as they realize something is wrong with their environment.

At the same time that we were looking at carbon transfer or energy transfer, we were also looking at defence signal transfers through those mycorrhizal networks.

Dr. Suzanne Simard, Professor of Forest Ecology, University of British Columbia, Canada

It’s mysterious that a plant would leak these particular compounds and that a fungus would pick them up and transmit them through their hyphae to another plant.  We haven’t seen this before, this flow of signalling molecules.

Dr Julia Amerongen Maddison, Forest and Conservation Sciences, UBC

Researchers have been trying to figure out what those signals are.  Now, they have an idea that certain chemical compounds are involved.

Mycorrhizal fungal networks linking the roots of trees in forests are
increasingly recognized to facilitate inter-tree communication through resource sharing, defence and kin recognition, and can thereby influence the behaviour of their neighbours.

What happens is that an injured seedling sends a defence signal.  The seedling that receives the signal, or that piece of communication, can then regulate their defence genes accordingly.

These genes start to produce more defence enzymes.  And in turn, those enzymes increase the defence of those seedlings against a potential attack by insects.

When you are scared, your body is producing chemicals that are telling your whole body that you are scared.  It’s getting your legs ready to run, and your arms ready to do whatever they need to do.

Those chemicals are specific for that purpose.  If those would leak out of your feet and something in the ground, let’s say a fungus, would pick up those chemicals and transmit them through the ground and someone else standing nearby would pick up those chemicals through their feet and get scared because they would get those scary chemicals in their body.  That’s what we are looking at with the trees.

Dr Julia Amerongen Maddison, Forest and Conservation Sciences, UBC

The Future of Our Remaining Forests

An aerial photograph showing a busy motorway junction. From "Intelligent Trees" Screenshot: NaturPhilosophieIs this survival of the fittest after all?  Maybe our own?  We use trees to provide wood for our homes, which are then built where these trees used to stand.

But can we afford continuing what is in effect slow deforestation?

Conserving those intelligent connections below the ground would mean doing forestry in a vey different way.

We need to change terminology.  We shouldn’t claim that we are tending to the forest when we are in fact utilizing wood.

Just as a butcher is not an animal keeper, a forester is no forest keeper.  Once we realize that we always destroy something when we use a chainsaw, we might start to treat the forest more carefully.

It’s possible to manage forests so gently that they can emulate pristine forest processes.

Peter Wohlleben, Forest Ranger, West Germany, Author of ‘The Hidden Life of Trees’

With over 8 billion people on Earth, we cannot go on cutting forest at such a brutal pace.  As our cities grow and we displace forests, have we unwillingly turned to enemies competing for the same land?

As long as there is a limit to logging, the forest will cope and recover.  But if humans take too much, it will be destroyed.

Can we find a sustainable alternative way to how we treat the forests so that we can coexist and preserve what is left?

Every single one of us can do something to help care for our forests.  Consume less.

We must take special care of our remaining old growth forests, because they are absolutely essential to slowing down climate change.

And because below the top soil is a huge store of information, yet to be fully understood.

Trees are indeed wise.  And they do talk.

We just need to tune into their language.