Mycorrhizal Networks: The Underground Internet of Forests?
Do trees really exchange resources and signals through underground networks? To answer that question, we need to understand mycorrhizae and mycorrhizal networks — partnerships between fungi and plant roots that have become a major subject of scientific research.
Contents
Remarkable symbiotic partnerships
Understanding mycorrhizal networks begins with the word ‘mycorrhiza’: a symbiotic relationship between fungi and plant roots. Mycorrhizal fungi form underground networks of microscopic hyphae associated with plant roots. Some fungi can connect with several plants within a community. The establishment of these associations is known as mycorrhization.
These networks are popularly nicknamed the forest’s underground internet, the internet of trees, or the “Wood Wide Web”, a play on the World Wide Web. In this symbiosis, fungi receive carbon compounds produced through photosynthesis from plants. In return, fungal hyphae can help roots access water and mineral nutrients more efficiently from the soil.
In ectomycorrhizal associations, fungal tissue surrounds fine roots. The fungal mycelium — the vegetative body of the fungus, made up of filaments called “hyphae” — forms a mycorrhizal mantle around the root without entering the plant’s cells. Different fungal species vary greatly in the range of plants with which they associate.
Other plants form endomycorrhizal associations, another form of symbiosis that is extremely widespread. These associations involve a closer contact between fungus and plant root cells. In arbuscular mycorrhizae, fungal hyphae enter cells in the root cortex and form highly branched structures called “arbuscules”.
La Forêt et le bois en 100 questions from the French Academy of Agriculture offers a detailed online introduction to these symbiotic associations for readers who want to go further.
More recently, research led by the French National Institute for Research in Digital Science and Technology (Inria), published in April 2025, helped visualise the remarkable structural complexity of mycorrhizal networks using advanced imaging analysis (see the example below).
Nutrient transfers and defence signalling
What do these symbiotic associations actually do?
A study by a team at the University of British Columbia in Canada, published in Nature in 1997, provided influential evidence that carbon can move between plants associated with common mycorrhizal fungi. This can involve carbon transfer in photosynthetically derived compounds between plants under particular experimental and ecological conditions. How important such transfers are in natural forests remains an active area of research.
In arbuscular mycorrhizal systems, the fine fungal network can greatly increase the effective absorptive area associated with roots and thereby improve access to nutrients and water.
Other research, including work published in Science in 2020, has examined the ways plants and fungi can be involved in information transfer and signalling through chemical compounds including volatile organic compounds (VOCs), organic acids and plant hormones. Experiments have reported changes in defence responses among plants connected by fungal networks under some stress conditions, such as herbivore attack. Neighbouring plants may then increase production of defensive compounds that deter or harm herbivores.
Limits and open questions about mycorrhizal networks
From a scientific perspective, the idea that this communication is conscious or intentional through mycorrhizal networks has not been demonstrated. Plants unquestionably have signalling and response mechanisms, but they do not possess a nervous system comparable to that of humans or other animals. There is currently no scientific evidence that plants experience feelings or pain in the animal sense.
More precisely, a plant can detect and respond to damaging conditions such as heat, cutting or drought without this implying subjective suffering. Molecules released during stress — including VOCs and compounds often discussed as phytoncides — read my article on the subject here — can function as biochemical signals. The familiar smell of freshly cut grass, for example, includes compounds released after tissue damage. Current evidence supports interpreting the chemical signals and nutrient exchanges described here as products of evolved biochemical and physiological processes.
Many scientists therefore warn against anthropomorphic interpretations that assign human intentions to plants, however attractive the metaphor may be. It is generally more precise to use terms such as ‘information transfer’, ‘signalling’ or ‘ecological interactions’.
At the same time, it is worth remembering how strongly our descriptions of nature are shaped by a human point of view. Science continually invites us to revise what we think we know — and, in my own spiritual practice, other traditions can also prompt useful questions about our relationship with the Living World. 😉
Many questions about mycorrhizal networks remain unresolved, despite the growing body of research.
Two examples are:
To what extent do below-ground exchanges influence forest ecosystem dynamics as a whole?
What are the long-term effects of these interactions on biodiversity and forest resilience in the face of climate change ?
A story to keep following — perhaps in a future article…
Come and experience forest therapy and discover the hidden world beneath your feet during my public walks in the Pays d’Ancenis area, between Nantes and Angers in western France (see the Forest Therapy Walks & Training section).
I also offer gift cards for forest therapy experiences — something to keep in mind for your next birthday. They are also a lovely way to share a memorable moment with a friend or family member.
Wishing you many beautiful walks in nature.
Comments