Tree Talk: Dr. Susan Simard by Sara Wright

Scientist Susan Simard is a professor of forest ecology at the University in Vancouver, British Columbia, who has been studying the below-ground fungal networks that connect trees and facilitate underground inter-tree communication and interaction. Over a period of more than thirty years this field scientist and her students have learned how fungi networks move water, carbon and nutrients such as nitrogen between and among trees as well as across species. Her research has demonstrated that these complex, symbiotic networks in our forests — at the hub of which stand what she calls the “mother trees” — mimic our own neural and social networks. This groundbreaking work on symbiotic plant communication has far-reaching implications that include developing sustainable ways to ‘manage’ forests, and to improve tree and plant resistance to pathogens. Although much of Simard’s research occurs in forests, she has also studied the underground systems of grasslands, wetlands, tundra and alpine ecosystems.

Under our feet there is a whole world of biological pathways that connect trees and allow them to communicate and share resources and information. Other scientists who study these networks (like Dr. Merlin Sheldrake) agree with Susan who suggests that the forest behaves as though it’s a single cohesive organism.

When Simard first studied forestry she discovered that the extent of the clear-cutting was alarming, and the spraying and hacking away of aspens and birches to make way for the more commercially valuable planted pines and firs was frightening. By the time she was doing graduate work scientists had discovered in the laboratory that one pine seedling root could transmit carbon to another pine seedling root, and Susan hypothesized that this kind of exchange was exactly what occurred in real forests. Although many believed she was crazy Susan finally procured funding for conducting experiments deep in the forest. She grew 80 replicates of three species: paper birch, Douglas fir, and western red cedar believing the birch and the fir would be involved in two way communication underground while the cedar would not (cedar and maple have a symbiotic relationship of their own). To test her idea she injected two isotopes of carbon into the trees (in plastic bags) and within an hour the birch and fir exchanged carbon through their root systems.

The carbon isotopes revealed that paper birch and Douglas fir were in a lively two-way conversation. It turns out at that time of the year, in the summer, that birch was sending more carbon to fir than fir was sending back to birch, especially when the fir was shaded. And then in later experiments, she found the opposite. Fir was sending more carbon to birch than birch was sending to fir, and this was because the fir was still growing while the birch was leafless. The two species were interdependent.

Douglas fir and birch were conversing not only in the language of carbon but also exchanged nitrogen, phosphorus, water, defense signals, allele (gene) chemicals and hormones.

Scientists already had learned that an underground mutualistic symbiosis called the ‘myco-net was involved in this exchange. Mushrooms are the above ground reproductive evidence of the underground fungal threads that form  mycelium, and that mycelium infects and colonizes the roots of all the trees and plants. And where the fungal cells interact with the root cells, there’s a trade of carbon for nutrients, and that fungus gets those nutrients by growing through the soil and coating every soil particle. The web is so dense that there can be hundreds of kilometers of mycelium under a single footstep. Mycelium connects different individuals in the forest, not just individuals of the same species but also works between species, like birch and fir. Hub or “mother trees” (can be male or female) have the most powerful fungal highways. These trees nurture their young, the ones growing in the understory. In a single forest, a mother tree can be connected to hundreds of other trees each of which can send excess carbon etc. through the mycorrhizal network to understory seedlings, but especially to their own kin. Mother trees recognize and colonize their kin with bigger mycorrhizal networks. They send them more carbon below ground. They even reduce their own root competition to create space for their seedlings to grow. When mother trees are injured or dying, they also send carbon and defense signals to the next generation of seedlings helping the youngsters to resist future stresses.Through back and forth conversations, trees increase the survival rate of the whole community.

 What makes the forest so resilient is that there are many hub or mother trees and many overlapping networks.

Unfortunately forests are also vulnerable, vulnerable not only to natural disturbances like bark beetles that preferentially attack big old trees but also to clear-cut logging. It is possible to remove one or two hub trees but not many of them; there is a tipping point after which the whole system collapses.

Trees may not have nervous systems but they can feel what is happening and can experience something analogous to pain. When a tree is cut it sends out electrical signals like wounded human tissue does.

Thirty years ago Simard hoped that her initial discoveries would change the way forestry was practiced. She was wrong. Forestry practices remain the same everywhere. In 2014, the World Resources Institute reported that Canada had the highest forest disturbance rate of any country worldwide, and that includes Brazil.

Massive disturbance at this scale affects hydrological cycles, degrades wildlife habitat, and emits greenhouse gases back into the atmosphere, which creates more disturbance and more tree diebacks.

Worse, foresters continue to plant one or two species of trees for harvesting and weed out other trees like aspens and birches. These simplified forests lack complexity, and they’re really vulnerable to infections and insect infestation. As climate changes this is creating a perfect storm for extreme events to occur.

Simard explains her frustrations with Western science. “We don’t ask good questions about the interconnectedness of the forest, because we’re all trained as reductionists. We pick it apart and study one process at a time, even though we know these processes don’t happen in isolation. When I walk into a forest, I feel the spirit of the whole thing, everything working together in harmony, but we don’t have a way to map or measure that.” In her view her research and that of others is exposing the limitations of the Western scientific method itself.*

The one hope is that forests as complex systems have an enormous capacity to self-heal. Simard has demonstrated this capacity with recent experiments in which retention of hub trees, and careful patch cutting can lead to regeneration and recovering species diversity.

Simard leaves us with three simple solutions:

  • Spend time in your forest, grassland etc – learn about local conditions of that particular micro-climate.
  • Save our old growth forests – these are the repositories of genes, mother trees, and mycorrhizal networks. We need this information to be passed on to the next generation of trees to help them withstand future stresses (as of 2019 we have less than 3 percent of our old growth forests left)
  • We must regenerate our forests with a diversity of species and genotypes by planting and allow for natural regeneration to occur.

Because it is January, the time of year that bears give birth I want to close this essay with a bear – tree – carbon networking story. On the west coast in the Pacific temperate rainforests bears sit under trees and eat salmon leaving their carcasses behind. Researchers have discovered that the trees are absorbing salmon nitrogen and then sharing it with each other through the underground network. According to the Smithsonian this creates an interlinked system: fish forest fungi.

Someone forgot to mention the role that bears play in this story; the last sentence should read: bears, fish, forest, fungi.



Using reductionism and the scientific mechanistic paradigm as a baseline – scientists can think, intuit, even sense but they can’t be allowed to feel. Our bodies carry our feelings/emotions. When we refuse to credit emotional intelligence as a form of knowledge we cripple ourselves. Without using our capacity to feel we can’t help but distort our perceptions, skewing results – scientific or otherwise. We need all our faculties to problem solve efficiently…. Field scientists and ethologists like me probably have a better handle on this than most because we are looking at a more holistic picture.

It is not surprising that most of the criticism of Simard’s research comes from scientists who immediately throw out the accusation that the researcher is anthropomorphizing the moment feeling enters the picture.


Sara is a naturalist, ethologist ( a person who studies animals in their natural habitats) (former) Jungian Pattern Analyst, and a writer. She publishes her work regularly in a number of different venues and is presently living in Northern New Mexico.

Author: Sara Wright

I am a writer and naturalist who lives in a little log cabin by a brook with my two dogs and a ring necked dove named Lily B. I write a naturalist column for a local paper and also publish essays, poems and prose in a number of other publications.

18 thoughts on “Tree Talk: Dr. Susan Simard by Sara Wright”

    1. How exciting! I wrote the article and find it amazing! Forests are amazing organisms who could teach humans so much about how to live sustainably and sanely if we allowed them sentience…

      We share 25 percent of our DNA with trees though we parted ways 1.5 billion years ago!

      Liked by 2 people

        1. Google the work of Susan Simard and that of Gagliano’s…field researchers have been learning amazing things about forests – the information is out there – and I will be writing more of what I learn as I go.

          Liked by 1 person

  1. Amazing! As I keep saying when a conversation turns to trees, I hate it when trees are cut down. At the same time, of course, I know that most houses are framed in wood and that paper is produced from wood pulp. Lots of paper means lots of pulped trees.

    I’ve heard of the underground network with which trees talk to each other. And it’s cool to think about that fish-forest-fungi network.What can we do to learn to be less reductionist and more humane and understand that we are all kin (children of our Mother Planet)–humans and furred, feathered, and finny people plus flowery and leafy people plus mineral people?

    And, still, I remember a song from Paint Your Wagon: “I talk to the trees, but they don’t listen to me.” Maybe the trees are too busy talking to each other to listen to a mere gold miner??


  2. Barbara, trees DO talk to us, but first we have to listen how to listen, and our western conditioning keeps us deaf to what they might be saying… walk quietly through any forest long enough and you will hear voices, I promise…

    As to what we can do? We could begin by attributing sentience to a species 400 billion years old… a species that learned how to cooperate long before humans evolved…

    Liked by 2 people

  3. Thank you so much for this post, Sara! I recently saw the film Fabulous Fungi which shows the fungi’s role in the great arboreal conversation and community. I love knowing that bears and salmon are part of this communion, that we can be too if we learn to listen. I feel lucky to live in mountains (the Shawangunks and Catskills) that have returned to forest after 19th century human industrial exploitation. Much of the regions forests are now protected from human depredation. Thank you for sharing your knowledge, intuition and compassion.


      1. Fantastic Fungi came four or five times by popular demand to our funky little art house collective cinema. That place almost never sells out, but it sold out each time for this film. I just looked it up online. I think it will eventually be available on netflix or youtube. Right now there’s a map of screenings. You can click on it and find out where the nearest one might be. I hope you get a chance to see it! Note: I misnamed it above. It is Fantastic Fungi–though clearly these beings are also fabulous!


  4. What a wonderful post, Sara! I just read BRAIDING SWEETGRASS, and something deep inside screamed that the tale of the pecan trees was so true, so true, and here is the evidence to prove its truthiness!! I feel so blessed to be in a world that is re-discovering the wonders of the worlds around us. We all need to find ways to tell others of these mysteries. Thank you so much for this post.


    1. Oh, when I say that writing it is my pleasure I mean it with all my heart…. we need to get the word out. Ironically I have felt that all plants speak and have very complex relationships so you can imagine my joy when I discover each new scientific facet…. note that it appears to me that WOMEN scientists have a better handle on this research than most men

      Liked by 1 person

  5. Thank you, Sara, for writing about the trees and their amazing communication system. Many of us have sensed for years that there was a lot more going on with trees than we learned in biology classes. How wonderful to hear of so much more that is being discovered! But then the Native Americans have long been saying “We are all related,” which of course includes the standing ones (trees).

    Liked by 1 person

  6. Yes, any of us who have loved plants and trees have known intuitively that these beings are very special – it’s too bad that we have to wait for science to validate what we already know…

    Frankly, this infuriates me.

    Indigenous peoples, as you say, have known all along.

    No mind body splits there… we are still being educated out of what we know.

    And I believe that because women think more holistically they have the edge – potentially.


  7. So many beautiful aspects to this Sara, thank you for sharing it. I had a few hours today and it was warmer than a usual January so I did a short walk-about in a local preserve. Among the things I was musing on was how frightened people are of the woods and how much they are missing by avoiding it. In my area we have tics and lime disease and people are really frightened of going into the woods. There were so many woodland birds and they all seemed to be singing.

    I wonder how much we, in our culture, have made the woods, the forest, nature in general, foreign to ourselves and how much that contributes to the destruction that we are seeing in all directions.

    Love to the trees!


    1. Fear of the woods is endemic to our culture, I believe – probably the result of the man against nature paradigm – and yes, this fear in my opinion has only too much to do with our need to destroy the planet.

      There is nothing more peaceful than walking in a forest and nothing to be afraid of. In Maine Lyme is a threat to my dogs – I can no longer walk them in the woods – but I do regularly wearing rubber boots. People have to see the sky – forests are so full of life that for many it is overwhelming. I’m struck here in New Mexico by the fact that so much new age/ positive thinking stuff acts as a wall of denial – everyone is standing on top of barren mountain tops raving at the views and oblivious to pollution etc – and it’s only really dark here for about a week – too much moonscape even at night – Give me a forest of trees and moon shadows….


Please familiarize yourself with our Comment Policy before posting.

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: