The Talking Trees

Great-Great Grandfather Oak stands sentinel overlooking Summit Valley Park sharing ancient wisdom with restored oak woodlands nearby and people who wander into the shade of his embrace seeking respite or perhaps a gentle turn on the swing. Photo by Flavia Potenza


From Santa Monica to the Oxnard plain, among the canyons which cut through the landscape to the ocean, Topanga is unique in its rich ecosystem of trees and shrubs. It is also unmatched in its residents’ commitment to preserving and protecting its native habitat and animal species

While most residents and visitors appreciate the beauty and diversity of this environment it is seen on the surface. But a mystery lies hidden below ground that few suspect. Some years ago an intrepid scientist named Suzanne Simard came to believe and later prove that a vast network connected forest trees, which nourish and sustain them by what must be called intelligence and communication.

A professor of forest ecology at the University of British Columbia’s Department of Forest and Conservation Sciences in Vancouver, Suzanne Simard studies the surprising and delicate complexity in nature. Her first revelation occurred when, decades ago, she and her grandfather rescued the family dog from a septic pit. As her grandfather dug into the muck she became fascinated with the root structure of the trees and the fungal network that accompanied them. In a TED talk given in July 2016 she explained, “…it was at that moment that I realized that that palette of roots and soil was really the foundation of the forest.”

Simard began studying forestry and in time found herself working with  commercial harvesters. But she was conflicted by the extensive spraying and hacking of birches and aspens to make way for more commercially valuable pines and firs. She went back to school.

At that time forestry scientists had just discovered, in the laboratory, that one pine seedling root could transmit carbon to another pine seedling root. Simard wondered, did  this happen in real forests? So she began conducting experiments deep in the forest.

Simard says, “I grew 80 replicates of three species: paper birch, Douglas fir, and western red cedar. I figured the birch and the fir would be connected in a below ground web, but not the cedar. It was in its own other world.”

She bought plastic bags and duct tape and shade cloth, a timer, a paper suit, a respirator, and then borrowed some high-tech equipment from her university: a Geiger counter, a scintillation counter, a mass spectrometer, microscopes. Next were syringes of radioactive carbon-14, carbon dioxide gas and some high pressure bottles of the stable isotope carbon-13 carbon dioxide gas.

“I pulled on my white paper suit,” Simard continues, “put on my respirator, and then put the plastic bags over my trees. I got my giant syringes and I injected the bags with my tracer isotope carbon dioxide gases. I injected carbon-14, the radioactive gas, into the bag of birch. And then for fir, I injected the stable isotope carbon-13, carbon dioxide gas. I used two isotopes, because I was wondering whether there was two-way communication going on between these species.”

After an hour she checked the results. She pulled the bag off the birch and ran the Geiger counter around the leaves, finding it had taken up the  radioactive gas. Then she checked the fir needles which were also responding. Simard checked all 80 replicates. The evidence was clear. The C-13 and C-14 was showing that the paper birch and Douglas fir were in a lively two-way conversation.At that time of the year, in the summer, the birch was sending more carbon to fir than fir was sending back to birch, especially when the fir was shaded. In later experiments, Simard and her team found the opposite, that fir was sending more carbon to birch than birch was sending to fir, because the fir was still growing while the birch was leafless. The two species were interdependent, like yin and yang.

Simard continues, “How were paper birch and Douglas fir communicating? Well, it turns out they were conversing not only in the language of carbon but also nitrogen and phosphorus and water and defense signals and allele chemicals and hormones — information.”

When walking through a forest we see mushrooms, the visible part of a fungal system. Threads from that system infect and colonize the roots of all the trees and interact with the root cells to exchange carbon for nutrients. Like all networks it is composed of nodes and links. The biggest and busiest are called “hub trees.” The  hub trees are connected to hundreds of other trees. The hub or “mother trees” nurture their young by sending excess carbon through the network to seedlings, increasing their survival rate by four times.

Simard continues, “I wondered, could Douglas fir recognize its own kin? So … we grew mother trees with kin and stranger’s seedlings. And it turns out they do recognize their kin. Mother trees colonize their kin with bigger mycorrhizal networks. They send them more carbon below ground. They even reduce their own root competition to make elbow room for their kids. When mother trees are injured or dying, they also send messages of wisdom on to the next generation of seedlings. So we’ve used isotope tracing to trace carbon moving from an injured mother tree down her trunk into the mycorrhizal network and into her neighboring seedlings, not only carbon but also defense signals. And these two compounds have increased the resistance of those seedlings to future stresses. So trees talk. Through back and forth conversations, they increase the resilience of the whole community.”

Simard says, “We need to regenerate our forests with a diversity of species and genotypes and structures by planting and allowing natural regeneration. We have to give Mother Nature the tools she needs to use her intelligence to self-heal. And we need to remember that forests aren’t just a bunch of trees competing with each other, they’re super-cooperators.”

Understanding that Simard’s work would apply to other large forests, we queried her about it;s application to lesser wooded areas like those in Southern California, including Topanga. Her reply was yes, it would apply to local forests. (But we’re still not  sure that Topanga’s trees can be considered a forest. We also asked if the interaction between tree species would apply here. She said yes.

This suggests the present practice of cutting down non-native trees and plants in favor of indigenous species should be revisited. If non-native trees thrive in this ecosystem, why not trust Nature to do what it does best? Instead of imposing an ideological limit, planting more and diverse species might prove the better goal.

Preserving the trees of this world is not a matter of aesthetics and recreational activities; it’s one of survival.

Nahuatl is the native language of the indigenous people of Mexico. One of their proverbs says, “When the last tree dies, the last man dies.”


By Bob Mendel


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