I’m not much of a hiker or outdoors person, but I’ve done enough walking through the forests of the Pacific Northwest to appreciate their beauty and complexity. I kind of knew, in a vague abstract way, that the trees and the wildlife were connected in a whole ecosystem.

Finding the Mother Tree: Discovering the Wisdom of the Forest completely changed how I think about trees and forests.

The author, Dr. Suzanne Simard, is a Professor of Forest Ecology at the University of British Columbia. During a career spanning thirty years Simard has published over 200 peer reviewed papers focused on how trees communicate using below-ground fungal networks. Her work partly inspired The Overstory by Richard Powers, a novel about trees and people which I reviewed here back in July.

Finding the Mother Tree is Simard’s first book. It’s a memoir that explores her life, career, and research. It’s beautifully written and absolutely fascinating.

Finding the Mother Tree
By Suzanne Simard
Alfred A. Knopf, New York, 2021

The Fungus Under Us

Simard’s research on trees is mainly about what happens underground, in their roots. It turns out that trees, and many other plants, are connected to the soil and to each other by complex networks of fungi. I’ll try to explain this briefly.

When we think about fungi (c’mon, admit it, you occasionally think about fungi) most of us probably think of mushrooms. Well, mushrooms are actually the fruit of the fungus, used to produce the spores by which the fungus reproduces. The main body of a fungus lies underground. It’s called the mycelium. A mycelium consists of a tangled mass of long branching filaments called hyphae. These hyphae are typically just 4-6 microns in diameter. (A micron is a millionth of a meter). By contrast a human hair is about 70 microns in diameter, so hyphae are pretty much invisible to the human eye.

Many species of fungi have hyphae that bind with the tips of tree roots, forming what is called a mycorrhizal network, a symbiotic relationship between a fungus and a tree. The hyphae help tree roots absorb water and nutrients like nitrogen and phosphorus from the soil. In other words, hyphae connect trees to the soil. In return, trees pass some of the sugars they make from photosynthesis down through their roots to nourish the hyphae. (Hyphae bind with the roots of all kinds of plants, not just trees.)

Now here’s the cool part: through this underground fungal network, trees connect and communicate with each other.

In her early research, Simard discovered that neighboring birch and fir trees were involved in a two-way exchange of carbon through the hyphal network. Trees of different species were supporting each other.

Later, Simard learned that mature trees – which she calls Mother Trees – support their descendants through this same network, sending water and nutrients to help them survive during their vulnerable early years under the forest canopy until they became self-sufficient.

Network Effects

Finding the Mother Tree taught me how trees are connected to each other in a tangible, down-to-earth, down-in-the-earth way. Even more amazing, Simard shows how trees form interdependent communities similar in many ways to human communities, cooperating, sharing resources, nurturing their young.

This connectedness extends beyond the trees. Simard has found a relationship between trees and salmon. It’s fairly well known that trees growing along riverbanks stabilize the soil and shade the water from the sun’s heat. This helps provide a welcome habitat for salmon and other species. Simard tells us that when the salmon return to their native rivers and streams to spawn, they’re hunted by wolves, bears and eagles who carry their prey into the forests to eat. The leftover fish bones and flesh decay and provide nitrogen to the soil which is absorbed by the trees and can be detected in their rings.

The trees protect salmon habitat and the salmon nourish the trees. 

Life at the Speed of Trees

Finding the Mother Tree tells the story of Simard’s life and research. It’s very detailed. Simard takes paragraphs to describe a handful of earth and pages to describe some of her experiments. The book moves slowly. Sometimes it’s hard to detect any movement at all, especially when she’s trying to convince government bureaucrats to change forest management policies. Yet it’s not boring. On the contrary, I found it incredibly interesting.

Her experiments move slowly too, often taking years to show results. In 2015, she started The Mother Tree Project, a study that will run for a hundred years.

At some point I realized that Simard was telling her story at a tree’s pace.

Her writing is beautiful, almost lyrical at times. You can feel her passion for the forests and her joy when she’s among the trees. Here, for example, she’s describing her discovery of a stand of Douglas fir trees perfect for a project to map out mycorrhizal networks:

“Adrenaline pulsed in my ears; I’d found just what I’d been looking for—a hill slope from creek to crest covered with Douglas fir of all ages. The oldest giants looked thirty-five meters in height, branches with plenty of muscle to shower seeds every few years into the shadowy beds packed with needles and humus. The youngsters sprouting from this veil looked like kids in a schoolyard: cohorts of seedlings and saplings flocking and scattering under the watchful gaze of towering teachers. From the road, the tree line seemed as complex as the Manhattan skyline.” [p. 238]

Connectedness is the central message of Finding the Mother Tree. Like many environmentalists, Simard urges us to stop thinking of the environment as something separate and apart from ourselves, just a resource to be exploited. We humans are part of the environment, embedded within it. We need to learn from the trees:

“This begins by recognizing that trees and plants have agency. They perceive, relate, and communicate; they exercise various behaviors. They cooperate, make decisions, learn, and remember— qualities we normally ascribe to sentience, wisdom, intelligence. By noting how trees, animals, and even fungi—any and all nonhuman species—have this agency, we can acknowledge that they deserve as much regard as we accord ourselves. We can continue pushing our earth out of balance, with greenhouse gases accelerating each year, or we can regain balance by acknowledging that if we harm one species one forest, one lake, this ripples through the entire complex web. Mistreatment of one species is mistreatment of all.

The rest of the planet has been waiting patiently for us to figure that out.” [p. 294]

Forests produce oxygen, filter the air, clean the water and store vast amounts of carbon. We must act urgently to save them. Despite the climate crisis we’ve caused, Simard remains hopeful. Her research has shown that densely connected forests are resilient and can heal themselves as long as the damage is not too extensive.

If we can save the forests, they might just save us in return.

Thanks for reading.

Related Links

How Smart is a Forest?
Interview with Suzanne Simard on the People I (Mostly) Admire podcast, January 20, 2023

How trees talk to each other
TED Talk by Suzanne Simard from June 2016

Mother Trees Connect the Forest
A short video in which Simard describes the idea of Mother Trees, 2011

Simard, S., Perry, D., Jones, M. et al. Net transfer of carbon between ectomycorrhizal tree species in the field. Nature 388, 579–582 (1997). https://doi.org/10.1038/41557
Early paper published in Nature first showing the transfer of carbon between birch and Douglas fir trees in the field.