The Wood Wide Web: What Simard's Research Actually Shows

“Simard showed that trees share carbon through mycorrhizal networks, preferentially supporting kin. This is not metaphor. It is documented carbon transfer. The question is what it means for how we understand intelligence.”

Suzanne Simard's 1997 Nature paper is the most cited paper in plant communication research. It showed that Douglas fir and paper birch trees growing together exchange carbon through mycorrhizal fungal networks, the fir sending carbon to the birch in summer when the birch is shaded, the birch returning carbon to the fir in autumn. The exchange is bidirectional, responsive to seasonal conditions, and follows kin recognition patterns: mother trees preferentially allocate carbon to their own seedlings through the network.

Carbon transfer through shared fungal networks has been reported in several studies, but how often it happens in natural forests, and how much it matters to the trees, is disputed. What it means conceptually is more contested. Simard uses the language of communication and intelligence; critics argue the word 'communication' implies intentionality that the mechanism doesn't support, the carbon transfer is a consequence of mycorrhizal fungal behavior, not necessarily coordinated by the trees themselves.

A 2023 review by Karst et al. in Nature Ecology & Evolution engaged this debate directly, finding positive citation bias and overinterpreted field results, arguing that the 'wood wide web' framing has outpaced the evidence, that many popular accounts of inter-tree communication describe a degree of coordination and intentionality that the underlying mechanism doesn't require.

For Narby's argument, the Simard finding matters as one of several empirical pillars supporting the claim that plant intelligence is a legitimate research object. Whether the specific mechanism is 'communication' in a strong sense matters less than the fact that plants are embedded in information-exchanging systems that Western science had previously overlooked entirely.

Sources

• Simard et al., Nature (1997)
• Simard, Finding the Mother Tree (2021)
• Karst et al., Nature Ecology & Evolution (2023)