Few ideas in modern ecology have travelled as far as the wood wide web, the notion that trees in a forest are wired together through underground fungi, trading carbon and even warning each other of danger. The idea was born in British Columbia, it is being stress tested in British Columbia, and the fiercest scientific fight over it is largely a Canadian affair. What the evidence actually shows is messier, and more interesting, than either the popular story or the backlash suggests.
Born in a BC clearcut
In 1997, Suzanne Simard, then a forestry researcher in British Columbia and now a professor at the University of British Columbia, published experiments showing that paper birch and Douglas fir seedlings in the field exchanged carbon in both directions, apparently through shared mycorrhizal fungi colonizing their roots. Mycorrhizas are ancient partnerships in which fungal filaments extend a root system enormously, delivering water and nutrients in exchange for sugars. When one fungus links the roots of several trees, it forms a common mycorrhizal network, and Simard’s work suggested resources could flow across it.
From that seed grew two decades of research, the Mother Tree Project, a long term experiment spread across dozens of sites in BC’s interior forests, and a set of popular claims: that big old trees nurture their seedlings, that dying trees bequeath carbon to neighbours, that forests behave a little like societies.
The pushback, also from Canada
In 2023, a high profile review led by mycorrhizal ecologist Justine Karst at the University of Alberta argued the popular story had run far ahead of the data. The critics did not deny that mycorrhizal fungi matter, but contended that field evidence for widespread resource sharing through networks was thinner than advertised, that some canonical experiments had alternative explanations, and that citations had drifted toward overstatement.
The reply came in January 2025, when Simard and colleagues published a detailed response in Frontiers in Forests and Global Change, affirming that inter-plant transfers through fungal connections have been demonstrated repeatedly while conceding that the size and direction of those transfers vary widely between forests, seasons and species. Read side by side, the two camps agree on more than the headlines imply.
| Reasonably settled | Genuinely contested |
|---|---|
| Mycorrhizal fungi are essential partners for most trees | How often networks move ecologically meaningful amounts of carbon |
| Fungi can physically link roots of different trees | Whether transfers favour kin or seedlings in any directed way |
| Carbon transfer between plants has occurred in experiments | Whether trees send warning signals through networks in nature |
| Soil fungal diversity declines with intensive harvest | How much network effects shape whole forest dynamics |
Fire is the new laboratory
British Columbia’s recent record wildfire seasons have pushed the research somewhere urgent. Work co-authored by Simard published in March 2026 examines how vegetation recovers after fire depending on burn severity, part of a broader effort to understand how soil fungal communities survive fire and how they influence which forests grow back. Related UBC research is tracking arbuscular mycorrhizal fungi in temperate rainforest soils altered by logging and climate change. If intact fungal communities speed regeneration, that becomes a practical argument, independent of the wood wide web debate, for leaving living trees and untouched soil patches inside harvested and burned areas.
Why it matters beyond the lab
The stakes are concrete in a province that replants hundreds of millions of seedlings. If seedlings establish better near mature trees and their fungal partners, then retention forestry, which leaves standing trees scattered through cutblocks, beats bare clearcuts on biology and not just aesthetics. Plantations of a single species, planted into soil stripped of its fungal diversity, may be the forestry equivalent of a monoculture farm: productive until stressed, then fragile.
Underground biology has a way of preserving its own history: the same soils that host living fungal networks also archive genetic traces of forests long gone, as researchers reading ancient DNA from Canadian permafrost have shown. The wood wide web may end up remembered less as a settled fact than as the argument that forced forest science to look down, and Canadian forests are where the answer is being dug up, one root tip at a time.
