Tree Speak and the Wood Wide Web

Traditionally, we have viewed trees as individuals, stoic as they compete for sunlight, survive storms, and slowly grow from tiny seeds to monstrous sentinels. This viewpoint is human, a sort of anthropomorphized version of a natural-resource economy or a misunderstanding of Darwinism. Only the strong trees endure, as they gobble up the supplies needed to survive. These ideals dominated forestry and ecology through much of the 20th century.

As our understanding of physical sciences matured, we learned many of the notions of individualism on the planet are fiction. Ecological systems of all sizes display intricate levels of interdependencies. The Earth itself can be viewed as a system of ecologies; all matter on the planet interacts. Plants break down rocks. Weather systems push energies across the globe. You breathe air molecules once exhaled by Geronimo. And, of course, the connectedness doesn’t stop at the boundaries of our atmosphere. Everything we are was born in stars. As Carl Sagan often said, “we are all made of star stuff,” and he wasn’t employing a metaphor. To view anything as an individual is a myth crafted by our consciousnesses.

So, it comes as no surprise that the trope of loner trees is patently false. As dendrologists learn more and more about trees, we have begun to understand that these woody plants display some incredible traits not normally attributed to non-animals. Instead of mute agents of photosynthesis, they are communicating networkers, purveyors of tree-talk.

Old-growth stand of beeches in Belgium - photo by Donar Reiskoffer

Research shows that trees act as communities instead of individuals. The communities, in this case, are not simply a group of entities that share resources by happenstance. Trees have developed, over 400 million years on Earth, what some scientists term the Wood Wide Web. Through this matrix, they communicate with each other and share resources, forming something akin to insect colonies, which spread intelligence and food among members.

Though the leaves and crowns of trees draw our eyes, the magic happens in the areas we cannot see. Walking through a forest, one often encounters a wealth of mushrooms. Like the trees, these organisms feature a large portion of their bodies underground. With the help of fungi, healthy forests contain what scientists call mycorrhizal networks. Filaments from fungi coat the wispy ends of tree roots. This physical meeting provides an overt symbiosis: fungi get to consume sugars the trees produce, while trees get nutrients that the fungi slurp from the soil. But this combination is not a simple bartering of goods.

The mesh created by trees and fungi creates a literal network, by which nearly every tree in a forest is connected. They employ chemicals, hormones, and electrical pulses to send information to other trees. If a tree lacks something – sugar, water, nitrogen – it sends a signal through the network. Bigger trees with better access to sunlight will then divert sugar or nutrients to spots that need it. According to forester Peter Wohlleben, trees that wrench themselves in odd directions, hoping to find sunlight, are the aberration in a forest, not the norm. Parent trees will provide nutrients for younger ones, overriding the need for all trees to have direct sunlight. Scientists have taken to calling these helpers “Mother Trees.”

Graphic of a mycorrhizal network created by Charlotte Roy, Salsero35, and Nefronus

With a bit of consideration, this sort of communal nature makes more sense than the survival of the fittest among individuals. 

Ecologist Suzanne Simard told Smithsonian Magazine, “Actually, it doesn’t make evolutionary sense for trees to behave like resource-grabbing individualists. They live longest and reproduce most often in a healthy stable forest. That’s why they’ve evolved to help their neighbors.”

As it turns out, trees that can monopolize sunlight do produce more sugar and grow faster, but ultimately are vulnerable and live for shorter periods. Forest systems produce much better results for trees across the board. Keeping the forest floor cool and damp maintains the network and provides the soil in which trees flourish. Wind damages individual trees far less in healthy groves, as they are buoyed by the crowns of their neighbors, causing fewer blowdowns and uprootings. Stable forests allow for a spread of ages, which is vital for several reasons. Clear-cut a forest and any returning trees will be saplings, which are sitting ducks for tree-eating animals. These regions are also prone to fungi that don’t play nicely. Older, healthy trees provide cover for these threats, while also fostering new life. The cycle is able to continue.

An acacia tree - photo by Judgefloro

Trees don’t only use the network to talk to each other, though.

One of a giraffe’s favorite meals is the leaf of the acacia tree. When the long-necked mammals start to munch on them, the trees recognize the injury and send out a signal in the form of ethylene gas. When another acacia “smells” the gas, they put on armor, pumping tannin into their leaves, hoping to deter the giraffes from eating them. Tannins can sicken or kill animals in large quantities. In an interesting evolutionary song-and-dance, giraffes caught on to this process. They now tend to eat into the wind, so ethylene won’t reach their next target. If it’s not windy, they learned to walk a distance greater than the gas can travel in still air before partaking anew. The giraffes discovered the trees were communicating!

According to Wohlleben, trees can also “taste.” Elms and pines can detect the saliva of leaf-eating caterpillars. When they notice the saliva, they release pheromones that draw wasps that eat the caterpillars. Trees can also detect deer. When deer saliva is noticed, trees produce foul-tasting chemicals to deter the foragers. Researchers know this behavior is deer-specific because injuries caused by humans or weather do not produce the same chemicals. The wounds of one tree can often protect others in the network or area.

Simard’s research showed that trees can distinguish between their own seedlings and those introduced from outside groves. She also demonstrated that trees of different species can produce networks with each other. Apparently, forests are healthiest not only when the variety of ages is widespread, but also the type of tree.

These findings have vast implications for logging. Modern foresters believe they can harvest trees like crops such as corn or wheat. Grow them, cut them down, and replant them. But the more we learn about forests, the more this method seems to be incorrect. New plantings lack mycorrhizal networks and tend to lack species variety, as companies prize certain trees for lumber. Forests managed by Wohlleben in Germany have shown an alternative is feasible. After spending decades as a lumber harvester, he began to manage forests as if they were giant systems. In these systems, trees could still be logged, but in a more sustainable way. Trees became larger, which meant fewer needed to be harvested to make profits. The networks were maintained and the ecosystems remained healthy.

Diagram of fungal network that links a group of trees, showing the presence of highly connected “mother trees" - graphic by BEILER ET AL 2010

Some scientists liken the communication and networking of trees to the neurons in systems with brains, raising the beings to near-sentient levels. To others, this attribution is more anthropomorphism. The contrarian viewpoint holds that just because entities can develop and recognize chemical and electrical signals does not mean they can “talk,” even if they can alter their behavior after receiving those signals. This take correlates to trees to evolved sensors.

My sense lies somewhere in the middle. Humans have a tendency to compare other things to humans because that’s what we know, but we also have the tendency to place ourselves above other organisms. Are trees a step away from Tolkien’s talking ents? Perhaps not. Is it possible that other forms can communicate in ways that we can’t really comprehend? Every extraterrestrial novel or film I’ve encountered tells me yes. Just because an entity might not talk the way we communicate does not automatically preclude their method from legitimacy.

A generation ago, we had no idea that mycorrhizal networks existed. We viewed trees as lone wolves, instead of families with Mother Trees. Our understanding of this system is nascent, as well. Could the communication system be more sophisticated than we glean even now? The answer to this question is certainly yes.

The next time you meander through a forest, spend some time thinking about it as a unit, instead of a collection of individuals. As you tread over a leaf-strewn floor, ponder the organic computer network running beneath your feet and wonder what the trees are saying at that moment.

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