The Network Itself
Mycorrhizal associations between fungi and plant roots are ancient — fossil evidence places them at roughly 450 million years ago — and nearly universal. More than 90 percent of terrestrial plant species form some kind of mycorrhizal relationship. The fungi colonise plant roots and extend far into the surrounding soil, dramatically increasing the plant's effective root surface area and improving access to water and minerals. In return, the plant provides the fungus with carbohydrates produced through photosynthesis.
What makes these networks ecologically interesting is that a single fungal individual can connect the root systems of multiple plants simultaneously. In a forest, this creates an interconnected web through which carbon, water, and nutrients can potentially flow between trees. The existence of this network is not in dispute. What is disputed is what it means.
What the Evidence Actually Shows
The most carefully conducted studies have demonstrated that carbon can move between connected trees via mycorrhizal networks under controlled conditions. In some experiments, labelled carbon from a large, light-exposed tree has been detected in smaller, shaded seedlings connected through the same fungal network. This is a genuine finding with interesting implications for how we understand carbon cycling in forest ecosystems.
Claims go considerably further in the popular literature. Books and documentaries have suggested that trees actively send carbon to struggling neighbours, that mother trees deliberately nurture their offspring, and that forests function as cooperative superorganisms with something resembling collective intelligence. These claims are not supported by the experimental evidence with anything like the certainty their popular presentation implies.
The transfer of carbon through mycorrhizal networks is real but modest in most field conditions. It is also bidirectional and governed by concentration gradients rather than any directional intent. The amounts transferred are typically small relative to a tree's total carbon budget. And crucially, the fungi themselves are not passive pipes — they are organisms with their own interests.
The Intelligence Question
The suggestion that plants possess something like intelligence is scientifically legitimate as a research question. Plants do respond to stimuli in sophisticated ways. They can detect light direction, gravity, touch, damage, and the presence of competing roots. Some responses involve electrochemical signalling that has a superficial resemblance to neural activity.
Whether these processes constitute anything meaningfully called intelligence depends almost entirely on how you define the term. If intelligence requires a nervous system, subjective experience, or deliberate decision-making, then plants almost certainly do not possess it. If intelligence means only the capacity to produce adaptive responses to environmental information, then plants qualify — but so do thermostats and immune systems, which dilutes the concept considerably.
Why It Matters Anyway
None of this means mycorrhizal networks are unimportant. The ecological implications of interconnected root systems are real and significant. Forest resilience, carbon sequestration, and the recovery of disturbed ecosystems may all be influenced by the health of mycorrhizal communities. The network is a genuine feature of forest ecosystems worth studying carefully.
The problem is not the science but the story layered over it. When popular accounts attribute intent, emotion, and social solidarity to trees, they produce a warming narrative that people find compelling — but they do so at the cost of accuracy. Understanding what mycorrhizal networks really do is both scientifically important and, in its own way, more remarkable than the stories we have been telling about them.