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Claim check

Do trees talk to each other through fungal networks?

Disputed

Specialists actively disagree, and the disagreement is substantive.

Fungi really do connect plant roots, and carbon really does move between trees below ground. The elaborated story — that networks are ubiquitous, that transfers matter to the recipient, and that mature trees preferentially feed their kin — was examined by two independent reviews in 2023 and found unsupported by the primary literature.

The claim as it circulates

“Forests are connected by a wood wide web, through which mother trees recognise and feed their own seedlings and warn each other of danger.”

Where you may have met it: Best-selling popular science books; Documentary features on forest ecology; Widely shared explainer videos and infographics

Taking it apart

What was claimed
That forests function as cooperative networks in which fungal connections let trees share resources and information, with old "mother trees" directing support to their own offspring.
What was actually observed
A 1997 field experiment detected carbon moving between birch and Douglas fir seedlings, with a small net transfer. A 2016 study found labelled carbon from mature spruce in the roots of neighbouring trees. A 2013 pot experiment found broad bean plants connected by fungi mounting defensive chemistry when a connected neighbour was infested with aphids.
What the evidence supports
That mycorrhizal fungi connect plants, that carbon moves between trees below ground, and that under controlled conditions something informational can pass between connected plants.
What it does not support
That such networks are widespread in real forests, that the quantities transferred matter to a receiving tree, or that trees preferentially supply relatives. Carbon detected near a seedling may have been used by the fungi rather than by the plant, and labelling designs generally cannot tell the difference.

Where researchers disagree

Two independent reviews in 2023 concluded that the headline claims are not supported by the primary literature, and one documented strong positive citation bias in how the field has been cited. Researchers associated with the original work dispute that framing and argue the evidence base is stronger than the reviews allow. The disagreement is genuine, current, and about scale and function rather than about whether anything moves at all.

What makes this case unusually instructive is that the drift is documented. The 2023 review did not only assess the evidence; it traced how the studies had been cited, and found positive results being cited far more often than negative ones, with claims growing in the retelling. That mechanism is not specific to forests, and it is worth recognising elsewhere.

Go deeper

The claims underneath

Each one carries its own evidence, scope and caveats. Expand any of them to reach the studies.

The idea that "mother trees" deliberately feed their own seedlings is not supported by the evidence

Contested

Researchers actively disagree, and the disagreement is substantive.

Systematic and critical reviews find that three widely repeated claims — that common mycorrhizal networks are ubiquitous in forests, that they transfer resources to seedlings in quantities that matter, and that mature trees preferentially supply related seedlings — are not supported by the primary literature, and that citation patterns have amplified positive results.

Who this applies to
the temperate forest systems where the idea originatedDo not extend this beyond the taxa listed — the popular version over-reaches.
Studied in
Pseudotsuga menziesii, Betula papyrifera, Picea abies

You may have heard

“Forests are connected by a wood wide web through which mother trees feed their young.”

The underlying observation — carbon moving between trees below ground — is real. The elaboration into deliberate, kin-directed nurture came from popular books and documentaries rather than from the measurements, and two independent reviews have now found the specific claims unsupported. It is an unusually clear case of a story travelling faster than its evidence.

Why we rate it this way, and what the caveats are
ContestedModerate confidence

Two independent reviews reached similar conclusions, which is significant. They are reviews rather than new data, researchers in the field dispute their framing, and absence of strong evidence is not proof the phenomena are absent.

How far it can be extended

The reviews concern the specific systems the original claims were built from. Extending either the claim or its rebuttal to forests generally would repeat the error being criticised.

Caveats

  • This does not mean fungal networks are fictional, or that carbon does not move between trees.
  • The reviews are literature analyses, not new field measurements.

Where researchers disagree

  • Researchers associated with the original work dispute the reviews' framing and argue that the evidence base is stronger than the reviews allow.
  • Field experiments do detect below-ground carbon movement, so the disagreement is about scale, direction and function rather than about whether anything moves at all.

Still unanswered

  • How common are common mycorrhizal networks in real forests?
  • What experiment could show whether transferred resources actually benefit a receiving seedling?

Last reviewed 2026-08-09

The evidence (3 studies)

Carbon does move between trees below ground

Well supported

Good evidence backs this, though some details remain open.

Isotope-labelling experiments in the field have detected movement of carbon between trees of different species, including between mature trees, with mycorrhizal fungi the most likely route.

Who this applies to
the temperate forest tree species tested so far
Studied in
Betula papyrifera, Pseudotsuga menziesii, Picea abies, Fagus sylvatica
Why we rate it this way, and what the caveats are
Well supportedModerate confidence

That carbon moves is well evidenced by two independent field experiments. What is far less certain is how much, by which route, and whether the receiving tree benefits at all.

How far it can be extended

Detected independently in North American and European forests, in seedlings and in mature trees, using different labelling approaches.

Caveats

  • Carbon found in a neighbour's roots may have been used by the fungi rather than by the tree.
  • Net transfers measured were small relative to a tree's total carbon budget.
  • Labelling designs struggle to exclude movement through soil rather than through fungi.

Still unanswered

  • How much of the transferred carbon is actually used by the receiving tree?
  • Is the fungus a conduit, a trader, or the main beneficiary?

Last reviewed 2026-08-09

The evidence (2 studies)

In pot experiments, plants connected by fungi respond to a neighbour being attacked

Emerging evidence

Real findings exist, but too few or too recent to be settled.

Broad bean plants connected by intact mycorrhizal mycelium produced aphid-repellent and parasitoid-attracting volatiles when a connected neighbour was infested; plants whose fungal connections were severed did not.

Who this applies to
broad bean plants with one fungal species, in pots
Studied in
Vicia faba

You may have heard

“Plants talk to each other through the wood wide web.”

A controlled pot experiment showed defensive chemistry appearing in a connected neighbour and not in a disconnected one, which is a real and careful result. Turning that into forests holding conversations skips several unanswered questions, starting with what the signal is.

Why we rate it this way, and what the caveats are
Emerging evidenceModerate confidence

The mesh design cleanly separates fungal connection from soil chemistry, which makes the result credible. It is one crop species, one fungus, in pots, with the signal itself unidentified.

Caveats

  • A pot experiment with a single crop species and a single fungus.
  • The nature of the transmitted signal is unknown.
  • No demonstration that this operates at meaningful scales in a wild ecosystem.

Still unanswered

  • What is the signal?
  • Does anything comparable happen in a forest, where networks are far more complex?

Last reviewed 2026-08-09

The evidence (1 study)

Go deeper

Mycorrhizal networks

The fungi are real. The forest internet, as usually described, is not.

Last reviewed 2026-08-09