Finding the Mother Tree: Discovering the Wisdom of the Forest

by Suzanne Simard

There is a necessary wisdom in the give-and-take of nature—its quiet agreements and search for balance. There is an extraordinary generosity.

Chemicals identical to our own neurotransmitters. Signals created by ions cascading across fungal membranes. The older trees are able to discern which seedlings are their own kin. The old trees nurture the young ones and provide them food and water just as we do with our own children. It is enough to make one pause, take a deep breath, and contemplate the social nature of the forest and how this is critical for evolution. The fungal network appears to wire the trees for fitness. And more. These old trees are mothering their children.

This is not a book about how we can save the trees. This is a book about how the trees might save us.

Planting seedlings with naked roots in the soil was insufficient. The trees seemed to need helpful fungal symbionts too.

“The Coast Salish say that the trees also teach about their symbiotic nature. That under the forest floor, there are fungi that keep the trees connected and strong.”

By now, I knew that there were more than a hundred species of mycorrhizal fungi in this forest. About half were generalists, colonizing both paper birch and Douglas fir in a diverse network. An intricately woven rug. The other half were specialists, with fidelity to either birch or fir, but not both.

What was known was that older forests had a greater variety of fungi than plantations did, and these suites of species especially associated with old trees were thick and fleshy and robust and able to access resources sequestered in hard-to-get-to corners of the soil. They unlocked essential nutrients that had been held tightly for centuries, in tenacious complexes of humus and mineral particles.

By collecting mushrooms over the seasons and years, Dan and I had figured out that the old-growth forests contained special old-growth fungi. Some only showed up in particularly rainy months and years, and some appeared only once. Others fruited only in dry months, while some mushrooms flushed no matter the season. We’d also dug up roots of birch and fir in forests ranging from a few years to hundreds of years old. We’d analyzed their DNA and compared it to data in a universal genetic library to determine the fungal species.

ectomycorrhizas.

“It’s as you thought,” he said, pointing at histograms proving that clear-cutting and removal of birch was detrimental to the long-term productivity of the forest. The numbers showed that forest growth declined with each successive one-hundred-year cutting-and-weeding cycle. Without the companionship of birch, with its microbes transforming nitrogen along mycorrhizal networks and bacteria helping guard against root disease, the growth of pure Douglas-fir stands declined to half of that evidenced in mixtures with birch. Birch, on the other hand, maintained its productivity without fir. According to this model, it didn’t seem to depend on fir for anything. “But I bet it does in some other way,” I said, leaning in for a kiss.

Ecosystems are so similar to human societies—they’re built on relationships. The stronger those are, the more resilient the system.

Root begets fungus begets root begets fungus. The partners keeping a positive feedback loop until a tree is made and a cubic foot of soil is packed with a hundred miles of mycelium. A web of life like our own cardiovascular system of arteries, veins, and capillaries.

Amazing

Yes, that’s it. Mother Trees. Mother Trees connect the forest. This Mother Tree was the central hub that the saplings and seedlings nested around, with threads of different fungal species, of different colors and weights, linking them, layer upon layer, in a strong, complex web.

If the mycorrhizal network is a facsimile of a neural network, the molecules moving among trees were like neurotransmitters. The signals between the trees could be as sharp as the electrochemical impulses between neurons, the brain chemistry that allows us to think and communicate. Is it possible that the trees are as perceptive of their neighbors as we are of our own thoughts and moods?

Could information be transmitted across synapses in mycorrhizal networks, the same way it happens in our brains?

“This outbreak is so intense most trees can’t fend off the bugs. They’ve even detected the swarms with satellites,” I said.

If dying trees communicate with incoming species, we might use this knowledge to better assist the migration of tree species as the old forests become maladapted to their native places. A warning-and-aid system—those infested Douglas firs telling pines to upgrade their defense arsenal, for instance—might be important for the growth of the new species or races (genotypes) as the old forests were dying back. As the injured Mother Trees slowly folded their cards, did they transmit their remaining carbon and energy to their offspring? As part of the active dying process. Like senescing grasses, handing over their remaining photosynthates to boost the next generation. Maybe they just dispersed the content of their dying cells randomly to the rest of the ecosystem, since energy is neither created nor destroyed.

What the trees were conveying made sense. Over millions of years, they’d evolved for survival, built relationships with their mutualists and competitors, and they were integrated with their partners in one system. The firs had sent warning signals that the forest was in danger, and the pines had been poised, eavesdropping for clues, wired to receive the messages, ensuring the community remained whole, still a healthy place to rear their offspring.

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 all other creatures.

The data also showed that injury, whether by western spruce budworm or the shears, induced the Mother-Tree seedlings to transfer even more carbon to her kin. Facing an uncertain future, she was passing her life force straight to her offspring, helping them to prepare for changes ahead. Dying enabled the living; the aged fueled their young.

This brings me to another adventure, one I’m still exploring because it speaks so graphically to the species connections we overlook. Scientists before me have discovered that the nitrogen from decayed salmon lives in the rings of trees along the rivers from where they came. I wanted to know whether salmon nitrogen was absorbed by mycorrhizal fungi of the Mother Trees and transmitted through their networks to other trees deeper in the forest. Even more, were the salmon nutrients in the trees declining with the reduction in salmon populations and habitat loss, causing the forests to suffer? If so, could this be remedied?

believe this kind of transformative thinking is what will save us. It is a philosophy of treating the world’s creatures, its gifts, as of equal importance to us. 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.

Mistreatment of one species is mistreatment of all. The rest of the planet has been waiting patiently for us to figure that out. Making this transformation requires that humans reconnect with nature—the forests, the prairie, the oceans—instead of treating everything and everyone as objects for exploitation. It means expanding our modern ways, our epistemology and scientific methodologies, so that they complement, build on, and align with Aboriginal roots. Mowing down the forests and harvesting the waters to fulfill our wildest dreams of material wealth just because we can has caught up to us.

Scientists now are more willing to say that forests are complex adaptive systems, comprised of many species that adjust and learn, that include legacies such as old trees and seed banks and logs, and these parts interact in intricate dynamic networks, with information feedbacks and self-organization. Systems-level properties emerge from this that add up to more than the sum of the parts.