The ‘wood wide web’: what is confirmed and what isn’t

You have probably heard of the ‘wood wide web’. Underground, the story goes, mycelium links trees together, and old ‘mother’ trees use it to feed their young. It is a lovely story, but how true is it? Below we go through three scientific papers: what in this story is confirmed, what isn’t, and why the debate is not yet settled.

What do we mean by a fungal network?

Scientists talk about a ‘common mycorrhizal network’. This is where the threads of mycorrhizal fungi, the hyphae, connect the roots of several plants underground, of the same species or of different ones. That is how Karst and colleagues define it in their review ¹.

One thing to be clear about from the start: none of the three papers claims that such connections don’t exist. The disagreement is about something else: how widespread they are, what passes through them, and whether the plant that receives something actually benefits.

Are networks present in forests everywhere? This is not confirmed

Karst and colleagues published their work in Nature Ecology & Evolution. It is a review: the authors went through studies that had already been published and checked what actually follows from them. Their conclusion is that the claims that networks are widespread in forests and that resources flow through them to the benefit of seedlings are not sufficiently supported. The results of field studies differ too much from one another, allow other explanations, or are too limited to support general conclusions.

The wording is harsher still on the central image of the popular story. The claim that mature trees preferentially send resources and defence signals to their offspring is not backed by a single peer-reviewed paper, that is, an article that other scientists checked before publication ¹.

This review has the same limit as any review: it assesses whether the published evidence is sufficient. A lack of evidence does not mean the phenomenon doesn’t exist. It only means there is currently nothing on which to assert it.

So where does all the confidence come from? From the way papers are cited

If the evidence is thin, why has the story taken such firm root? The second part of the same review is about scientific texts rather than the forest: how studies on networks are cited in them. The authors counted that over the last 25 years the number of insufficiently supported claims has doubled. In their view, researchers are more willing to cite positive results, and this may distort the overall picture of how networks in forests are built and how they work.

The authors sum up cautiously: knowledge about networks is still too limited and too unsettled to base forest management on it ¹.

Does carbon pass from tree to tree? Apparently yes, but how much is unclear

If the general claims are shaky, a simpler question remains: does anything measurable pass through the network at all? Henriksson and colleagues, in New Phytologist, re-examined the evidence for the mother tree hypothesis. This is also a review of other people’s work, not a new experiment. Their conclusion: there is as yet no evidence that a significant net transfer of carbon goes through the networks and benefits the recipient. ‘Net’ here means what is left with the recipient after subtracting the flow in the opposite direction.

Why is this so hard to test? Isotope labels are usually used. A plant is given carbon marked with a special variety of atom, and researchers look to see where the label ends up. The method is good for tracing the flow of substances. But the mycorrhizal partnership is complex, the sensitivity thresholds of the instruments are low, and natural differences in isotopes are small. As a result, conclusions are sometimes drawn from tiny shifts, and this can be misleading.

At the same time, the authors acknowledge that some carbon transfer does, apparently, take place ².

How much carbon can come from a neighbour? In the strongest case, 40%

The highest figure came from the work of Klein and colleagues, 2016, which Henriksson and co-authors cite as the main argument of the supporters. Klein and colleagues studied 40 m tall trees of different species with overlapping roots and found a two-way exchange of photosynthesis products. According to their conclusion, 40% of the carbon in a tree’s fine roots had been obtained from other trees through networks.

Together with the data of Avital and colleagues, 2022, this is the highest published estimate of how much carbon a plant receives from another. Most other studies give figures 10–20 times lower. And the main caveat: at the time of writing, it has not been conclusively shown how much of such flows go through the network rather than by other routes ².

The location, the tree species and the number of trees in these studies are not given in our source. So the 40% cannot be carried over to any other forest: it is the result of a single study, not a rule.

Where did the ‘mothers’ come from? According to critics, from a wish to humanise trees

The third paper deals not with figures but with the image itself. Robinson and colleagues, in Trends in Plant Science, dispute that ‘mother trees’ pass a substantial amount of carbon through the network to their offspring and to neighbouring seedlings. There are no new measurements here. It is a critical article, and the authors rely on recent reviews according to which the evidence is unconvincing or absent altogether.

They see the root of the idea in a wish to humanise plants. In their view, this leads to misunderstandings and false interpretations and may ultimately harm rather than help the good cause of forest conservation ³. This is their assessment, not the result of an experiment.

Who is missing from this review? The supporters of the hypothesis

All three sources are written by critics of the hypothesis. The supporters’ side is represented only by the figures of Klein and Avital as retold by Henriksson and colleagues. Our selection contains no replies from supporters to this criticism. So the honest conclusion is this: the debate goes on, and neither side can be considered definitively right.

This debate has no bearing on the MicoRadar forecast. The forecast on the map is a calculation by our model, not an observation in the forest, and it does not rely on the theory of fungal networks.

What follows from this and what doesn’t

• None of the critics denies connections between roots through mycelium. It has not been confirmed that they are widespread and help seedlings.
• Some carbon transfer between trees apparently does occur. A significant net transfer that benefits the recipient has not yet been shown.
• There is no peer-reviewed evidence that old trees look after their own offspring in particular.
• The figure of 40% is the highest published. It does not describe all forests, and the route through the network has not been conclusively shown for it.
• The selection contains only critics. This is an open scientific question, not ready-made knowledge and not practical advice.

Checked against the sources on 3 October 2026.