“My instinct has always been to listen to what living things are saying.” With these words ecologist Suzanne Simard expresses the intention and passion that has guided her life-long striving to better understand the natural world. Her forebears and relatives lived from logging forests in western Canada. She knew the logging world well, and yet she was always interested in what makes nature thrive, in what brings more life. Throughout her training to become a scientist and in her later work as a Canadian forest service researcher and then professor, she often had to navigate between conventional forest practices and theories, and her underlying sense of their inadequacy. She describes this journey in her book, Finding the Mother Tree – Discovering the Wisdom of the Forest (New York: Alfred A. Knopf, 2021).
At the age of 20, she had a seasonal job working for a logging company. Her task was to assess the health of the prickly spruce seedlings that had been planted after large areas of subalpine fir forest had been clear cut. She was disturbed to find so many unhealthy seedlings with yellowing needles. The seedlings had hardly connected with the soil, making them easy to pull out of the ground. The contrast to a young healthy subalpine fir growing nearby was striking:
I uprooted it to compare. Unlike the planted spruce, which I’d plucked like a carrot out of the soil, these sprawling fir roots were anchored so tightly that I had to plant both feet on either side of the stem and pull with all my might.... I was amazed to see the same bright yellow fungal threads wrapped around the root tips as I’d seen in the old-growth forest.... Digging a little more around my fir excavation, I found the yellow threads infusing the organic mat that capped the soil, forming a network of mycelium that was radiating farther and farther afield.
She did not know what the significance of this mycelium network — which consists of fungal threads — might be. But the observation led to a question that motivated and guided her work for the next 40 years: “But what exactly were these branching fungal threads, and what were they doing?”
The manifold discoveries she (and later her students) made showing the connections between soil, fungi, and trees were not easily gained. She worked in a man’s world of forestry with its emphasis on clear-cut logging. In an early job for the Canadian forest service she carried out experiments related to a practice called “free-to-grow plantations.” The theory behind this practice was that if you minimize competition with other plants, the trees will grow best. Her first experiments involved applying herbicide (glyphosate) to all the plants that were growing around and above all the young seedlings that had been planted in a clear-cut area a few years before. “I loved learning how to conduct an experiment in the forest but hated turning these plants into ghosts.” Her gut feeling was that the notion of getting rid of all the competition to improve the growth of the plantation trees was misguided. “Here I was, a soldier in a war I didn’t believe in.”
In a related experiment, she eradicated assumed competitors and found that “all but one of the treatments would end up failing to improve conifer growth and, no surprise, native plant diversity was lowered. In the case of birch, killing it improved the growth of some of the firs but caused even more to die — the opposite of expectations.”
When she landed a permanent research position with the Canadian forest service, she was finally able to carry out research that focused on discovering how diversity might enhance rather than inhibit the healthy growth of trees. Simard carried out a variety of experiments over many years with ingenuity and great perseverance. Some led to her earning advanced degrees. Her doctoral work included the study of the relation between the growth of birches (considered bad weeds by free-to-grow forestry) and valued Douglas fir seedlings. Along the way she discovered that these two species share a variety of mycorrhizal fungi.
Their threads (mycelia) connect the roots of the two plants with each other. She planted paper birch, Douglas fir, and Western red cedar (as a control, since it doesn’t share mycorrhizal fungi with the other two) in groups; she deeply shaded some of the Douglas fir seedlings, while others were lightly shaded or left unshaded. This was intended to mimic shade conditions that could occur naturally due to the growth of broad-leaf trees like birches.
Simard made a remarkable discovery. The intricate procedures applied in the experiment involved using two different isotopes (carbon-13 and radioactive carbon-14) in carbon dioxide. Carbon-14 was added to bagged air around birch and carbon-13 to bagged air around Douglas fir. The leaves of a plant take up carbon dioxide from the air to make sugars. If carbon-14 could be detected in the tissue of Douglas fir, or carbon-13 in the tissue of birch, then she would know if the plants were, via the mycorrhizal connection, exchanging sugar sap. The experiment, which spanned two growing seasons, showed that the carbon isotopes were in fact being exchanged. The Douglas fir seedlings received more sugar from the birch than vice versa. The greater the shade, the more transfer of sugar from birch to fir. “Birch was cooperating in lockstep with fir.” Birches have a high rate of photosynthesis and were evidently passing on surplus sugar to the firs, especially in shady conditions when the firs on their own would only be able to grow slowly. This was the first field experiment to show that different tree species were exchanging substances via their fungi connection.
This research was featured on the cover of Nature in 1997 and drew lots of attention. It contributed to a burst in research into the underground interconnectedness of plants that continues to this day. In the second half of the book, Simard describes extensive research that she and her colleagues and graduate students have carried out. She also makes clear how the logging industry and regulatory agencies, with their focus on short-term gains and the rigid paradigm of eliminating competition to stimulate growth, have been very slow to acknowledge the reality of mutual enhancement through diversity in a plant community.
Her book culminates in the discussion of “mother trees.” She and her students discovered extensive mycorrhizal networks connecting the trees within an area of a forest. And it is the biggest, oldest trees that have the most connections and they have the ability to share their substances with other trees and young saplings. So when we picture individual trees in a forest, we are picturing an abstraction. Below ground they are dynamically woven into each other.
Toward the end of the book, Simard summarizes vividly her journey as a researcher:
I’d been taught in the university to take apart the ecosystem, to reduce it into its parts, to study the trees and plants and soils in isolation, so that I could look at the forest objectively. This dissection, this control and categorization and cauterization, were supposed to bring clarity, credibility, and validation to any findings. When I followed these steps of taking the system apart to look at the pieces, I was able to publish my results, and I soon learned that it was almost impossible for a study of the diversity and connectivity of a whole ecosystem to get into print. There’s no control! the reviews cried at my early papers. Somehow with my Latin squares and factorial designs, my isotopes and mass spectrometers and scintillation counters, and my training to consider only sharp lines of statistically significant differences, I have come full circle to stumble onto some of the indigenous ideals: Diversity matters. And everything in the universe is connected—between the forests and prairies, the land and the water, the sky and the soil, the spirits and the living, the people and other creatures.
Simard refers to the knowledge and practices of Aboriginal peoples of western North America. They can speak of trees as “people,” as beings, that have agency and are wise. This resonates strongly with her, and at the same time she must acknowledge that she cannot “presume to grasp Aboriginal knowledge. It comes from a way of knowing the earth — an epistemology — different from that of my own culture.” I know this feeling well.
The epistemology of Western culture, which modern science epitomizes, starts with the implicit and sometimes explicit premise of separation or disconnect: I – world; subject – object; inner – outer; spirit – matter. In her scientific work, Simard embodies the epistemology of separation and at the same time, through her strong sense of the connectedness of things, she has been able to use science to show connectedness. And yet she realizes there is still a gulf between scientific knowledge that points to connectedness and a living awareness of being connected, such as that she feels in Aboriginal knowing.
For me this felt tension leads to important questions. Say I have begun to glimpse, as Simard has, the fundamental connectedness of things. In other words, I have begun to realize that separate “things” don’t exist in the living world. Can I then begin to practice a way of knowing that takes, from the outset, connection as a reality? How, then, would world (me-in-world; world-in-me) appear? Only then might I understand and bring to realization my agency as part of world agency.