How Trees Secretly Communicate and Protect Each Other

Susan Simard loved nature from early childhood. She grew up in a family of foresters and spent every summer in the vast forests of Canada. Surrounded by trees and wilderness, she developed a deep connection to the natural world.

As she grew older, she studied forestry and began working for companies that harvested trees and replanted others, planning and managing forests. Over time, Susan noticed a puzzling pattern. The more she tried to improve forests by removing trees she considered unnecessary and planting new ones, the more the forests seemed to suffer. They became more vulnerable to disease and often lacked essential minerals. In contrast, forests that were left largely untouched appeared healthier and more resilient.

These observations led her back to academia in search of answers.

An Underground Communication System

While continuing her studies, Susan encountered new research describing a system called mycorrhizae, tiny fungal filaments that connect tree roots underground. These filaments form a vast network that allows trees to exchange nutrients and signals.

Intrigued, she began investigating the phenomenon in depth. She discovered that forests are interwoven with communication networks that resemble a modern system of underground cables.

As extraordinary as the idea sounded, she demonstrated it in a simple way. She injected one tree with a radioactive isotope, and soon afterward traces of the isotope appeared in surrounding trees. The evidence showed that trees exchange substances through an underground network. In other words, trees engage in a form of organic communication.

Trees That Help One Another

Further tracking of these transmissions revealed remarkable details. The communication between trees is not constant but changes according to need.

A tree that lacks carbon because of weather conditions or soil quality reaches out through the network to trees that have more. Those trees then send minerals through the fungal connections, making the transfer largely one sided.

The research also showed that trees give priority to their own offspring. A Douglas fir, for example, provided mineral support primarily to seedlings that originated from itself and shared its genetic material.

Trees maintain a certain reserve of minerals for themselves. Yet as a tree nears the end of its life, it transfers its remaining reserves to other trees in the network.

It may sound unbelievable, but these findings are supported by scientific research. Trees live in families and communities. They communicate, support weaker members, and even help ensure the survival of future generations.

Warnings and Cooperation

Trees can also warn one another of danger.

In one case, a fir tree that was wounded by a parasite sent warning signals through the network. Nearby trees responded by producing protective enzymes, which helped them survive the attack.

The communication network operates through fungi. In return for carrying nutrients and signals, the fungi receive sugar produced by the trees, something they cannot produce on their own. The relationship benefits both sides.

A Forest That Functions Like a Brain

Susan Simard and her colleagues mapped a section of forest and discovered that the communication networks resemble synapses in a brain. The forest functions as a vast interconnected system with hubs and nodes of communication.

In this sense, the forest operates almost like the large brain of a living organism.

This insight suggests that before cutting down a tree, it is important to understand its place in the network. Removing a tree that plays a central role could affect many other trees, while removing a more isolated tree may have little impact. Only after such an assessment can we know whether cutting a tree will cause significant harm to the forest.

This area of research is known as the neurobiology of plants, and there is still much to discover about the hidden life of forests.