Bonus Ep: Suzanne Simard and the Social World of Trees

Suzanne Simard, speaking from a Powell’s Books event about her book Finding the Mother Tree, walked listeners through her arc from growing up in a logging family to becoming a forest ecologist who uncovered the extent and function of the Wood-Wide Web. She described early work in industry where clearcutting and nursery-grown seedlings focused on above-ground growth left new plantations failing. That led her to study roots and fungi: mycorrhizal fungi form obligate, mutualistic links between roots and soil, transporting carbon, nutrients and water. In PhD work at Oregon State she used isotopic labeling (carbon-14 and carbon-13) in controlled experiments and found interspecies carbon transfer (e.g., paper birch donating carbon to Douglas-fir). Later, with graduate student Kevin Beiler, she spent five years sequencing fungal and tree DNA across an uneven-aged Douglas-fir forest to create a spatial map showing that most trees are linked, with the oldest, largest trees acting as hubs — the "mother trees." These hubs donate resources to seedlings and help bootstrap regeneration.

Simard explained the transmitted compounds are largely amino acids (her team estimated glutamate as a dominant mover), and the network’s architecture resembles biological neural networks: hubs, many connections and signaling that effectively lets trees perceive neighbor identity, kinship and stress. She defended the use of terms like "intelligence" for the functional resilience and information flow in these systems. The research challenged prevailing competition-centered forestry and provoked backlash after her Nature paper, but it has practical implications: conserve old trees and their groups instead of leaving lone residual trees, avoid wholesale conversion to single-species plantations, rethink salvage logging (dying trees contribute carbon to neighbors), and use locally sourced soil transfers or carefully managed inocula in restoration. She also addressed fire (networks can recover but severe combustion of the forest floor impedes fungi recovery for decades), advocated controlled burns where appropriate, and promoted assisted migration of genotypes combined with mother-tree conservation to match future climates. Throughout the conversation she tied her science to Indigenous ecological knowledge, climate mitigation (old growth as major carbon sinks), and civic action—urging public pressure, policy change and multifaceted approaches to protect and restore forests.