Beneath every forest runs a real network of hyphae connecting root to root—this is a microscopic fact documented for decades. What has changed in recent years is not the finding itself, but how it was interpreted: the most recent scientific review calls for considerably more caution about how much trees actually “converse” with each other through their fungi.
What a common mycorrhizal network is, structurally
When the hyphae of a single mycorrhizal fungus simultaneously colonize the roots of several trees, they form what is known as a common mycorrhizal network (CMN). Its physical existence is well established in forestry ecology literature: a single mycelium can, in fact, physically connect root systems of different individuals and even different species of trees.
The popular narrative and its limitations
The idea that these networks allow mother trees to send carbon, water, and warning signals to their seedlings—popularized under the term “Wood Wide Web”—captured the public imagination in the last decade. However, a review published in 2023 in Nature Ecology & Evolution examined how studies on common mycorrhizal networks are cited in scientific literature and found a troubling pattern: unsupported claims doubled in twenty-five years, a result of a systematic bias towards citing only positive results.
Revisiting the mother tree hypothesis
That same year, an exhaustive analysis in New Phytologist re-examined the original data supporting the mother tree hypothesis, noting that isotopic labeling methods—a central tool in these studies—are enormously sensitive to minimal variations that are difficult to interpret. The team's conclusion was clear: evidence of net carbon transfer that effectively benefits the recipient tree remains unconfirmed, and a role for the fungus as an altruistic pipeline between trees is also difficult to reconcile with any adaptive advantage for the fungus itself.
The voice of silviculture
A third group of researchers, this time from plant physiology and forest management, published a warning in Trends in Plant Science about the risks of personifying plant life: attributing maternal or altruistic intentions to an organism without a nervous system can lead to erroneous interpretations with real consequences for forest management policies.
Why scientific honesty matters more than metaphor
None of this denies the real elegance of the phenomenon: mycorrhizal fungi do build physical networks underground, and this subterranean architecture remains a legitimate object of wonder. But rigorous science demands distinguishing between what is proven—structural connectivity—and what remains a hypothesis under review—intentional communication and maternal altruism. At Simbiosis, we believe that curiosity is best sustained by evidence rather than metaphor, even when the metaphor is easier to tell.
References
- Karst J, Jones MD, Hoeksema JD. Positive citation bias and overinterpreted results lead to misinformation on common mycorrhizal networks in forests. Nat Ecol Evol. 2023;7(4):501-511. PMID: 36782032. DOI: 10.1038/s41559-023-01986-1
- Henriksson N, Marshall J, Högberg MN, Högberg P, Polle A, Franklin O, Näsholm T. Re-examining the evidence for the mother tree hypothesis - resource sharing among trees via ectomycorrhizal networks. New Phytol. 2023;239(1):19-28. PMID: 37149889. DOI: 10.1111/nph.18935
- Robinson DG, Ammer C, Polle A, et al. Mother trees, altruistic fungi, and the perils of plant personification. Trends Plant Sci. 2024;29(1):20-31. PMID: 37735061. DOI: 10.1016/j.tplants.2023.08.010