First Global Map Reveals Vast Underground Fungal Network and Its Climate Role

A new study presents the first global map of underground fungal (mycorrhizal) networks. By integrating data from 322 prior studies and 16,000 soil samples, researchers estimated the networks’ total length, biomass, and carbon-transport capacity.

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The team used high-resolution imaging, machine-learning, and robotic sampling to quantify fungal structures across diverse terrestrial ecosystems, allowing a planetary-scale assessment of network density and distribution.

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The analysis estimates the underground fungal network spans roughly 110 quadrillion kilometers and stores about 300 megaton of carbon—four to six times the mass of all humans. Annually, the networks move ~4 billion metric tons of CO2 into soils, representing ~11 percent of anthropogenic emissions. By transporting carbon into the soil and recycling nutrients, the networks contribute to ecosystem carbon storage, though lower density in agricultural soils could weaken these functions.

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The authors note that new imaging and computational tools now reveal previously hidden fungal infrastructure. They warn that agricultural conversion has halved network density relative to natural ecosystems, risking reduced soil carbon storage and nutrient turnover. They recommend preserving or restoring fungal connectivity to support climate mitigation and food security.

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Scientists warn that grasslands, containing ~40 percent of global arbuscular mycorrhizal biomass, are being converted to agriculture at a rate four times faster than forest loss, threatening fungal network integrity and soil carbon sequestration.

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• “With the advent of new technologies in high-resolution imaging, machine learning, and robotics, we are beginning to reveal what has long remained hidden beneath our feet,” — Corentin Bisot, coauthor

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• “It is difficult to overstate the importance and sheer scale of these fungi,” — Justin Stewart, lead author, Society for the Protection of Underground Networks

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• “A single teaspoon of soil can contain up to 10 meters of mycorrhizal network.” — Justin Stewart, lead author

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• “Mycorrhizal fungi have shaped life on Earth for hundreds of millions of years, yet we still know remarkably little about how the infrastructure of these living transport systems is distributed across the planet,” — Merlin Sheldrake, coauthor

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The authors propose expanding mapping to track temporal changes in network density, especially in intensively farmed regions, and integrating fungal network considerations into climate policy and agricultural management to preserve identified ecosystem services.

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