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Mycorrhiza: the alliance of tree and fungusWood Wide Web: a beautiful metaphor with real groundingTrees can warn neighbors with scentsHow trees defend themselves from pestsUnderground signals through fungal networks“Mother trees”: a beautiful hypothesis or a proven fact?Fungi are not wires, but independent organismsTrees constantly sense their surroundingsWhere science ends and myth beginsThe forest is a network of interconnections
This content has been automatically translated from Ukrainian.
Trees do not speak in human understanding, but they can exchange signals through fungal networks, roots, and volatile organic compounds. We explain what mycorrhiza is, how the “Wood Wide Web” works, what research supports this, and where popular notions of a “smart forest” exaggerate real scientific data.
In the forest, there is rarely true silence. Even if the songs of birds, the rustle of the wind, or the cracking of branches are not heard, life continues everywhere: in the leaves, bark, soil, roots, and microscopic threads of fungi beneath our feet. Trees do not have a voice, a nervous system, or a brain, but that does not mean they exist in isolation from one another.
Modern ecology increasingly shows that plants can respond to neighbors, pests, drought, light, diseases, and changes in the soil. They can release signaling chemicals, alter root growth, and enter into complex symbiotic relationships with fungi. That is why popular literature often says that trees “communicate.”
Of course, this is just a metaphor. Trees do not transmit thoughts to one another or have conversations like humans do. But there can indeed be exchanges of substances and chemical signals between them. This is what makes the forest not just a collection of individual trees, but a complex interconnected ecosystem.
Mycorrhiza: the alliance of tree and fungus
To understand the underground “communication” of trees, one must start with mycorrhiza.
Mycorrhiza is a symbiosis between plant roots and fungi. The fungus receives photosynthesis products from the tree—primarily sugars—in exchange for helping to extract water, phosphorus, nitrogen, and other minerals from the soil. This is extremely beneficial for the tree, as fungal threads—hyphae—are much thinner than roots and can penetrate the smallest pores of the soil.
In fact, the fungus significantly expands the area from which the tree can obtain nutrients and water.
Such alliances emerged a long time ago. Scientists believe that mycorrhizal fungi helped the first plants colonize land over 400 million years ago. Today, approximately 90% of terrestrial plants form some type of mycorrhiza.
In forests, ectomycorrhizal fungi are particularly important, as they envelop the roots of trees externally and form a complex underground network. This is what is associated with the well-known concept of the “forest internet.”
Wood Wide Web: a beautiful metaphor with real grounding
In the 1990s, Canadian ecologist Suzanne Simard studied the forests of British Columbia. In one of her most famous experiments, she demonstrated that carbon can be transferred between paper birch and Douglas fir through shared mycorrhizal fungi.
This work became one of the reasons for the emergence of the popular phrase Wood Wide Web—a kind of “worldwide web of the forest.”
The metaphor proved to be so successful that it quickly spread far beyond scientific circles. It creates an image of the forest as a vast network where trees supposedly exchange messages and help each other.
Partially, this corresponds to reality. Shared fungal networks do indeed exist. Through them, laboratory and field experiments have recorded the movement of carbon, nitrogen, phosphorus, and some signaling molecules.
However, it is important to remember: Wood Wide Web is just a fitting metaphor. The fungal network does not operate like the human internet. There is no conscious transmission of messages or a single control center. The movement of substances depends on many factors: the type of fungus, the condition of the trees, soil moisture, light, and even the time of year.
Trees can warn neighbors with scents
Underground connections are not the only way plants interact.
When leaves are damaged by insects, the tree begins to release volatile organic compounds into the air. These substances can be perceived by neighboring plants, which in turn activate their own defense mechanisms even before the pests reach them.
In other words, trees do not “scream” about danger, but the change in their chemical composition becomes a kind of signal for other plants.
Such mechanisms have been confirmed by numerous studies and are now considered one of the best-studied examples of plant communication.
How trees defend themselves from pests
Chemical signals serve another interesting function.
When caterpillars or other insects begin to eat leaves, the tree can release substances that attract the natural enemies of these insects—parasitic wasps or predatory insects.
In this way, the plant not only enhances its own defense but also alters the behavior of other organisms around it.
In modern ecology, there is even talk of two conditional channels of information transmission between plants: the “airborne” channel—through volatile organic compounds, and the “underground” channel—through roots and mycorrhizal fungi.
Underground signals through fungal networks
The roots of trees also actively interact with the surrounding environment. They release hundreds of different compounds that alter the composition of microorganisms in the soil, affect fungi, and can change the response of neighboring plants.
In laboratory experiments, researchers have repeatedly shown that plants connected by a shared fungal network sometimes respond more quickly to pest attacks or other stress factors.
However, caution should be exercised with conclusions here. A significant portion of such studies has been conducted under controlled conditions—in greenhouses or special containers. In a natural forest, everything is much more complex: dozens of species of fungi, thousands of roots, and countless other organisms interact simultaneously.
Therefore, today scientists agree: the transmission of signals through mycorrhiza is possible, but its significance for natural ecosystems is still actively being researched.
“Mother trees”: a beautiful hypothesis or a proven fact?
One of the most well-known ideas is the concept of “mother trees.” It suggests that large old trees can support young seedlings by transferring nutrients to them through fungal networks.
This idea gained immense popularity after Suzanne Simard's publications. It wonderfully aligns with the human perception of nature as a friendly community.
However, modern reviews of the scientific literature present a more cautious picture.
The existence of shared fungal networks is beyond doubt. But there is currently insufficient evidence that adult trees systematically “feed” young plants on a scale sufficient to significantly impact their survival.
In other words, resources can move between plants, but that does not mean that trees consciously “care” for one another.
Fungi are not wires, but independent organisms
Another common misconception is that fungi are sometimes imagined only as “cables” between trees.
In reality, they are separate living organisms with their own needs.
The fungus receives sugars from the tree, while providing it with minerals and water. If conditions change, the nature of this interaction can also change.
Therefore, it is more accurate to envision the fungal network not as a message transmission system, but as a complex ecological network where each participant primarily responds to its own needs.
Trees constantly sense their surroundings
Even without the help of fungi, trees continuously receive information about the surrounding world.
They respond to shading, lack of water, competition for resources, changes in soil composition, and the ratio of different wavelengths of light. If a competitor appears nearby, the tree may change the direction of growth of its shoots or roots.
Such reactions are not conscious decisions, but they indicate an extraordinarily complex system of perceiving the environment.
Where science ends and myth begins
Today, it can be confidently stated: trees are indeed capable of influencing one another through chemical signals, root interactions, and mycorrhizal fungi.
At the same time, we should not attribute human emotions or intentions to them. Expressions like “trees talk,” “friend each other,” or “care for their young” are artistic images that help popularize science but are not a literal description of natural processes.
In reality, plants respond to physical and chemical signals arising in the environment. This does not make them any less amazing—instead, it shows how complex ecosystems can be without the involvement of a nervous system or brain.
The forest is a network of interconnections
The more scientists study forests, the clearer it becomes: an individual tree cannot be considered in isolation from everything that surrounds it. It is connected to fungi, bacteria, insects, other plants, and soil through thousands of invisible interactions.
Perhaps this is the most interesting discovery of modern ecology. Not that trees are like humans, but that they have created their own way of interacting with the world—a slow, chemical, and almost invisible one to us. And the more closely we study the forest, the more we understand: behind its outward silence lies one of the most complex natural systems on Earth.
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