110 quadrillion km of AMF hyphae in topsoil

A study published in Science in June 2026 estimated the combined length of living hyphae of arbuscular mycorrhizal fungi in the top 15 centimetres of global soils at 1.10 × 10¹⁷ kilometres. The model's standard deviation is 0.13 × 10¹⁷ km. That is roughly 110 quadrillion kilometres, but the scientific notation is a better reminder that we are dealing with an extrapolation, not an unrolled and measured thread.

The team gathered data from 322 studies and more than 16,000 soil cores from nine biomes. Measurements of hyphal density were combined with environmental conditions and machine learning models in order to predict values in places without samples. Biomass was estimated separately. The method allows a step from many local measurements to a world map, but the result depends on how representative the samples are and on how well the spatial variables describe the underground environment.

The figure applies to the AMF group, not to all fungi, and not to a single connected "network wrapping the planet". The hyphae belong to an enormous number of organisms and local associations tied to roots. The model covers a defined soil layer; it does not describe the full depth, nor ectomycorrhizal hyphae. Comparisons with cosmic distances may work as an illustration of scale, but they do not replace those limits.

The value has an application as a reference point for monitoring. The authors showed the distribution of biomass and density, making it possible to ask which habitats hold exceptionally large amounts of mycelium and where a change in land use may reduce it. Further measurements should update the map rather than confirm one striking number.

What entered the model

The global model used 322 studies, more than 16,000 soil cores, nine biomes and measurements of over 300,000 hyphae. Its estimate for living arbuscular-mycorrhizal fungal hyphae in the top 15 cm of soil is 1.10 × 10¹⁷ km with a standard deviation of 0.13 × 10¹⁷ km. The corresponding biomass was estimated at about 300 ± 60 million tonnes.

These quantities were not produced by unrolling and measuring a global thread. The model transfers local measurements to areas with similar conditions. It excludes deeper soil and other mycelial types, and the standard deviation belongs beside the central value.