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Mycelium Networks — The Forest's Underground Internet

9 min read

Mycelium Networks — The Forest’s Underground Internet

Beneath a square meter of temperate forest soil, there may be hundreds of kilometers of fungal threads — hyphae — woven into networks that connect the roots of trees, shrubs, and plants across entire ecosystems. These mycorrhizal networks transport carbon, water, phosphorus, and nitrogen between plants. They transmit electrical signals that propagate through the network like action potentials in neurons. They can solve maze problems. They exhibit rudimentary memory. And increasingly, they are being studied as models for biological computing, as materials for space habitats, and as a lens on the nature of distributed intelligence.

Confidence: established (nutrient transport, electrical signals); emerging (information processing, “learning”); speculative (true computation, sentience)

Key Facts

  • ~90% of land plant species form mycorrhizal associations with fungi
  • The fungal mycelium in 1 teaspoon of healthy soil can total 1–3 km of hyphae
  • Mycelium produces action-potential-like electrical spikes — measurable by microelectrodes, propagating at 0.5–3 mm/s along hyphae
  • Andrew Adamatzky (UWE Bristol) was first to report spiking electrical activity in fungi and to develop “fungal computing” architectures
  • SPUN’s 2025 global map: using 2.8 billion fungal sequences from 130 countries, the Society for the Protection of Underground Networks released the world’s first high-resolution predictive biodiversity maps of mycorrhizal fungal communities globally
  • Mycelium can grow at ~1 cm/day; can survive space-analog vacuum conditions; absorbs radiation

The “Wood Wide Web” — Real but Oversimplified

The popular framing (trees talk to each other, mother trees feed their children) is based on real phenomena but substantially oversimplified:

What’s established:

  • Nutrients (especially carbon, phosphorus) move between plants via shared mycorrhizal networks
  • Defense signals (chemical, possibly electrical) propagate through networks — plants connected to attacked neighbors sometimes upregulate defenses before being attacked themselves
  • Older, larger trees (“hub trees”) are more connected in the network and can subsidize seedlings in low-light understory conditions

What’s contested — and the evidence is increasingly skeptical:

  • A 2024 meta-analysis by Karst et al. examined 28 field experiments on CMN nutrient transfer. Only 5 showed any potential transfer — and none demonstrated measurable impact on seedling survival or growth
  • The claim that “mother trees preferentially send resources to offspring via CMNs” has no peer-reviewed field evidence. The “Fantastic Fungi” narrative is not supported by controlled field experiments
  • A Nature Ecology & Evolution (2022, widely discussed 2024–2025) analysis found fewer than half of popular wood-wide-web claims trace back to actual evidence
  • With current technology, it is not possible to confirm that continuous, non-transient mycelial connections persist between trees in the field — networks may be far more ephemeral than assumed
  • The degree to which fungi act as mutualists vs. parasites is unresolved — some fungi exploit the network, extracting more than they contribute

Verdict: The networks are real. The “intelligent mother-tree communication” framing is romantic overreach without adequate field evidence. The truth is more complicated and more interesting — especially in the electrical signaling domain.

Cambridge University Press published Slime Mould and Philosophy (2024) — the first major academic philosophy volume on cognition in brainless organisms, addressing these exact interpretive disputes.

Electrical Signals and Proto-Computation

The most surprising recent research is on mycelium as an electrical computing substrate:

  • Fungi produce action-potential-like voltage spikes (~0.5–2 mV, duration ~5–10 minutes) that propagate along hyphae
  • Adamatzky’s group at UWE documented trains of ~50 spikes per minute in Ghost fungi (Omphalotus nidiformis); a 2025 FEMS Microbiology Reviews analysis found that spike-length distributions statistically match properties of human language — 50 distinct “words” in some species (contested but not debunked)
  • The spikes resemble neural oscillations: they can be entrained by stimuli, their frequency changes with environmental conditions (light, chemicals, temperature)

7-day oscillation cycle (Scientific Reports, July 2024): Researchers monitoring Pholiota brunnescens mycelium continuously for 100+ days found a week-long electrical oscillation — the longest periodic phenomenon ever recorded in fungi. The oscillation appeared at the food-bait location after ~60 days, coinciding with a directional shift in causal signal flow across the whole network. No mechanism is yet known.

Shape recognition (Fungal Ecology, September 2024, Tohoku University): Phanerochaete velutina mycelium placed in Circle vs. Cross arrangements of wood blocks responded differently to each geometry — allocating network resources differently based on spatial configuration over 116 days. Wood decay rates differed between the two geometries. The network appeared to “read” abstract spatial arrangements without sensory organs.

Spatial memory after severing (Fungal Ecology, 2024): When mycelial cord connections were completely severed after a fungus had oriented toward a food bait, the mycelium retained directional memory and resumed growing toward the bait’s remembered location. Spatial information is encoded in the network’s growth architecture — not just in continuous electrical state.

  • Memory: when repeatedly exposed to the same stimulus pattern, mycelium shows faster, more coordinated electrical responses — a form of biological learning. The network “remembers” without neurons.

Fungal Computing

Andrew Adamatzky’s lab has proposed and demonstrated early-stage fungal computers:

  • Information is represented by spikes of electrical activity
  • Computation is implemented in the mycelium network topology
  • The interface is realized via fruit bodies (mushrooms) as input/output nodes
  • Basic logic gates have been demonstrated

Shiitake memristors (PLOS ONE, October 2025, Ohio State University): The most significant bioelectronics result yet. Shiitake mycelium (Lentinula edodes) grown as functional memristors — the core component of neuromorphic computing — switched between resistance states at 5,850 times per second with ~90% accuracy (95% at optimal settings). After dehydration and rehydration, the devices retained their programmed resistance states — meaning fungal bioelectronic components could be stored dry and reactivated. The researchers also noted shiitake’s inherent radiation resistance, flagging aerospace computing applications.

Properties that make fungal computing interesting:

  • Self-repairing: damaged hyphae are regrown; computation continues
  • Self-organizing: the network topology adapts to resource distribution
  • Biodegradable — no rare-earth minerals required; can be grown on agricultural waste
  • Radiation-resistant (shiitake specifically) — relevant for space electronics
  • The mycelium network topology is a scale-free small-world network — the same graph architecture as artificial neural networks and the internet (measurable graph theory, not metaphor)

The memristor result is a proof of concept. Scaling to practical computing remains an open engineering challenge.

Cornell Biohybrid Robots (2024–2025)

Researchers at Cornell University’s Organic Robotics Lab developed the first biohybrid robot system converting mycelium electrical signals into digital commands — published in Science Robotics. The system:

  • Uses living mycelium as a sensor-actuator interface
  • Mycelium electrical signals control robotic motion
  • The living component senses and responds to environment; the machine amplifies and acts
  • First demonstrated robot that can receive real-time biological signals from fungal networks

This connects directly to concept-distributed-cognition and concept-octopus-intelligence — the mycelium network, like an octopus arm, is a distributed computation substrate that can act semi-autonomously.

Space Applications: NASA Myco-Architecture

NASA’s Mycotecture Off Planet project (Ames Research Center) received a Phase III NIAC award ($2M over 2 years) — this is not concept art but active prototype fabrication:

  • Proposed three-layer structure: outer layer of frozen Martian/Lunar ice (radiation shielding), middle layer of cyanobacteria (O₂ + nutrients), innermost layer of mycelium growing into habitable structure on-site
  • Astronauts carry dormant fungal spores (lightweight, compact); on arrival combine with locally available organic matter and water
  • Mycelium grows into structural forms over days, guided by molds
  • The resulting material rivals wood in strength, is fully biodegradable, provides radiation shielding

ISS test confirmed (2025): A PNAS 2025 paper tested fungal melanin + polylactic acid (PLA) biocomposites aboard the International Space Station in low Earth orbit, evaluating radiation protection and structural stability. Results confirmed viability. This is the first ISS-confirmed fungal material test.

Chernobyl connection: Radiotrophic fungi (e.g., Cladosporium sphaerospermum) grow toward radiation sources in the Chernobyl reactor, using melanin to convert gamma radiation into chemical energy via radiosynthesis — analogous to photosynthesis. This makes fungal melanin one of the most exotic radiation-protection materials known — and a direct inspiration for the space habitat design.

Closed-loop biomes: Mycelium can simultaneously perform water filtration, bioluminescent lighting, humidity regulation, and organic waste decomposition — a candidate for circular life-support systems on long-duration missions. The fungal circular economy aboard a generation ship is a genuine engineering proposal.

Cross-Realm Connections

  • concept-distributed-cognition: Mycelium networks are the botanical version of distributed cognition — no central processor, computation embedded in network topology. Same principle as octopus arm ganglia and slime mold computation.
  • concept-octopus-intelligence: Both mycelium and octopus arms are distributed processing systems capable of local computation without central control. They represent convergent solutions to the same architectural problem.
  • tech-generation-ship: Myco-architecture is a serious candidate technology for closed-loop life support in long-duration space missions — solving food, medicine, materials, and radiation shielding simultaneously.
  • event-bronze-age-collapse: Mycorrhizal network resilience vs. Bronze Age network fragility — distributed biological networks are highly resilient to node failures (any path through the network works); human trade networks were fragile to correlated failures.
  • concept-convergent-evolution: Electrical signaling in fungi, neurons, and plant vascular systems — convergent discovery of the same information-transfer mechanism across radically different lineages.
  • Textiles / concept-fabric-as-data: Mycelium can be grown into fabrics and leather-like materials. Bolt Threads (Mylo), Ecovative, Hermès-partnered Bolt Threads. The boundary between organism and material dissolves.

The Philosophical Problem

The hardest question: is a mycelium network computing, sensing, or alive in a richer sense than we assume?

The electrical signals are real. The learning-like responses are real. The distributed architecture is real. But “intelligence” implies representation of world models — and there is no evidence mycelium encodes representations. The behaviour may be entirely explicable by simple molecular gradients and electrochemical feedback without any form of processing that resembles cognition.

The same debate applies to concept-distributed-cognition in slime molds, immune systems, and markets. Where does chemistry become cognition?

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