What the wood wide web actually supports

The popular version is easy to want. Trees pass sugars and warnings through a fungal internet. Old trees feed young ones. A forest is a cooperative, and the mushrooms are the cables.

Some of the biology under that story is solid. The leap to intention is not.

What a mycorrhiza is

A mycorrhiza is a partnership between a plant root and a fungus. It is common enough to be the usual condition of most land plants, not a curiosity of a few famous trees. Two forms cover a lot of what a walker actually meets.

Arbuscular mycorrhizae reach inside the root cells. The association is ancient, and it turns up across a wide range of plants, including many crops. Ectomycorrhizae wrap the outside of a root in a sheath and grow between the outer cells. They are typical of a familiar set of forest trees — pines, oaks, and beeches among them — and the fungal partners are often the ones that also make mushrooms. Some of those partners are ascomycetes. Truffles are the famous case. The fungus is not decorating the tree. It is trading.

The trade, stated at textbook scale, is this. The plant has carbon, fixed from the air by photosynthesis, and shares some of it. The fungus is good at scavenging water and mineral nutrients, phosphorus in particular, and shares some of that. Both partners are organisms with a metabolism, not characters in a fable. The exchange can be large. It is still an exchange measured in experiments, not a conversation someone transcribed. What “mycorrhizal” means without the myth keeps that vocabulary honest.

Networks without a chat log

Hyphae can also connect the roots of more than one plant. Researchers have tracked labeled carbon and labeled nitrogen moving between plants in setups where fungal links were available. A movement is not automatically a message, and it is not proof that a tree chose to provision its offspring. How much moves, which way, and whether the transfer matters to the survival of either plant are live arguments. Even the share of that movement that truly passes through the fungus, rather than through soil or through roots that are touching, is argued. The disagreement is the topic. It is not a failure of the public to keep up.

Common mycorrhizal networks are a research subject, not a finished children’s story. Some experiments support meaningful transfer under particular conditions. Other work urges caution about overgeneralizing from pots to old-growth narratives. Holding both sentences at once is adult literacy.

“Wood wide web” and “mother tree” are metaphors from essays and talks. They are good at getting a person to care about a hidden partnership. They are bad at describing a mechanism. A shared network can move materials by physics and by the ordinary self-interest of a fungus. Neither requires the forest to be kind.

A cleaner human story

There is a cleaner human story beside this one, and it does not need the metaphor. People have used fungal fruiting bodies as material for a very long time. The man known as Ötzi, found in the Alps in 1991 and more than five thousand years dead when he was found, was carrying the tinder fungus Fomes fomentarius, a hard bracket still known for catching a spark. He was also carrying a birch polypore, Fomitopsis betulina, long filed as Piptoporus betulinus. Why the second fungus was in the kit is inferred. Nobody left a note. The find is enough: fungi were tools before they were a theory of the forest.

Food history carries another non-metaphorical thread — yeast, cheese rinds, cultivated mushrooms — told in Fungi in food history. Language carries a third: Mushroom and toadstool.

Wonder survives the trim. The partnership is real, it is old, and most of it happens where you cannot see it. What the evidence does not hand us is a forest that talks. Lifestyle categories — decomposer, pathogen, mutualist — blur in the field; Decomposers, pathogens, mutualists holds the map without pretending the borders are fences. Keep the partnership. Return the sermon.