Global Map of Mycorrhizal Fungal Networks: 110 Quadrillion Kilometers of Fungal Filaments in Soil

An international research team published the first global map of arbuscular mycorrhizal fungal networks in Science in 2026 — a milestone that makes the "Wood Wide Web" visible on a planetary scale for the first time. The study was led by the nonprofit organization SPUN (Society for the Protection of Underground Networks) and the AMOLF physics institute in Amsterdam. In this article, we summarize the study, put the impressive numbers into scientific context, and honestly explain what this map means for mushroom enthusiasts — and what it doesn't.

What the Global Map of Mycorrhizal Fungal Networks Shows

Arbuscular mycorrhizal fungi (AM fungi, botanically the phylum Glomeromycota) live in symbiosis with about 70% of all plant species. They form fine threads in the soil — called hyphae — and exchange nutrients like phosphorus for sugars from the roots of their host plants. The team compiled over 4,000 measurements from more than 16,000 soil samples, covering 9 of the 14 global biomes. Using machine learning (random forest models), the researchers predicted hyphal density for every square kilometer of land area — including regions never sampled before.

The result is the first spatially resolved map of this underground network. It shows that the highest densities are not found in tropical rainforests, but often in wild grasslands — from the Tibetan Plateau to the prairies of North America. If you want to zoom in yourself, check out the interactive display in the SPUN Underground Atlas. To see how spatial environmental data also come together in a mushroom app, check out the FungiFind Mushroom Map.

The Numbers — Correctly Contextualized

The study provides figures that are hard to grasp. To keep them reliable, here are the verified orders of magnitude:

• 110 quadrillion kilometers of hyphae: Laid end to end, the living AM hyphae in the top 15 cm of soil would stretch about 1.10 × 10¹⁷ km. That's hundreds of millions of times the Earth–Sun distance — an underground infrastructure of planetary proportions.
• ~300 million tons of carbon: That's the weight of this living hyphal biomass in the top 15 cm of soil — according to the study, about four to six times the biomass of all humans.
• ~1 billion tons of carbon per year: That's how much carbon plants channel annually into their AM fungal partners — equivalent to about 3.9 billion tons of CO₂ equivalent or roughly 11% of annual fossil fuel emissions.

An important note on accuracy: This roughly 11% describes the carbon flow that plants feed into the networks — not a permanently "stored" amount. Some of this carbon is respired or released again; some contributes to long-term soil carbon formation. AM fungi are thus a central but complex component of the global carbon cycle — not a simple CO₂ sink. For more background on such symbioses, visit the FungiFind Blog.

Agriculture Weakens the Networks

A key finding concerns agriculture: In cropland soils, the density of AM hyphae was on average about 50% lower than in natural soils (non-cultivated soils had roughly 47% higher densities on average). Plowing, fertilization, and fungicides disrupt the delicate fungal threads. The authors also emphasize the limits of their model — differences in management intensity could not be fully captured. Still, the direction is clear: Intensive land use reduces a network that is important for nutrient cycles, soil structure, and carbon sequestration.

Important for Mushroom Enthusiasts: AM Fungi Are Not the Mushrooms in Your Basket

Scientific honesty is needed here — especially because headlines can easily mislead. Arbuscular mycorrhizal fungi do not produce fruiting bodies that can be collected. They are microscopic and live entirely in the soil and plant roots.

The mushrooms that foragers seek — porcini (Boletus edulis), chanterelle (Cantharellus cibarius), fly agaric (Amanita muscaria), and many others — belong to a completely different ecological guild: They are mostly ectomycorrhizal fungi (ECM) or decomposers (saprotrophs). Ectomycorrhizal fungi envelop tree roots from the outside, rather than penetrating them like AM fungi. The new Science map thus describes AM networks and their role in soil carbon — it is not a "foraging map" for edible mushrooms.

What remains relevant for mushroom enthusiasts? The map tells us something about healthy soils and intact ecosystems. Where underground fungal networks thrive, the foundations for trees, forests, and indirectly for edible mushrooms are often better. But for the specific question "Where and when do I find porcini?", habitat, tree partners, soil, and weather remain decisive — exactly the factors that also go into the FungiFind Species Encyclopedia entry for porcini (Boletus edulis) and into the score model. Helpful to know: In the Underground Atlas, SPUN also maps ectomycorrhizal biodiversity — these data are thematically closer to forest mushrooms, but they are still diversity maps, not fruiting maps.

Conclusion: An Invisible Network of Planetary Significance

The first global map of mycorrhizal fungal networks makes visible how much life above ground depends on life below. 110 quadrillion kilometers of fungal filaments, about 300 million tons of carbon, a carbon flow on the order of 11% of fossil emissions — and at the same time a clear warning that intensive agriculture halves these networks. For us at FungiFind, the message is clear: Healthy soils and intact ecosystems are the foundation for all fungal diversity. Take a look at the FungiFind Mushroom Map and the Underground Atlas — and stay curious about the world beneath our feet.

Note: This article was created with the help of AI and editorially reviewed against primary scientific sources. It is for general information only and does not replace professional mushroom advice. Never identify or consume mushrooms based solely on apps or texts — when in doubt, consult a certified mushroom expert.