First Global Map of Underground Fungal Network Created

The Network Beneath Our Feet

A vast underground fungal network of almost unimaginable scale exists beneath the Earth's surface. For the first time, an international research team has created a global map of this mycorrhizal network—a system of fungal filaments that forms mutually beneficial partnerships with plants. The map reveals a total length of approximately 110 quadrillion kilometers, nearly a billion times the distance from Earth to the Sun. The findings were published in Science.

Symbiosis with Plants

Arbuscular mycorrhizal fungi form underground networks that support plant life and help regulate the climate. Through microscopic filaments called hyphae, they exchange water and nutrients for carbon produced by plants via photosynthesis. Current estimates suggest about 70% of all plant species depend on these partnerships for survival.

Building the Map

To create the first global map, the authors compiled data from 322 previous studies and 16,000 soil samples from a wide range of terrestrial ecosystems. Using machine learning and advanced imaging, they estimated the network's extent and biomass. Coauthor Corentin Bisot noted that new technologies are revealing what has long remained hidden beneath our feet, showing how fungal networks transport nutrients and help regulate the climate.

Carbon Transport and Scale

The researchers calculated that the underground network contains about 300 megatons of carbon in biomass—four to six times the total mass of all living humans. These fungal networks transport the equivalent of around 4 billion metric tons of carbon dioxide into the soil each year, representing approximately 11% of annual human-caused CO₂ emissions. Lead author Justin Stewart of the Society for the Protection of Underground Networks emphasized the difficulty of overstating the importance and sheer scale of these fungi.

Agricultural Concerns

The study also issued a warning: the density of fungal networks in agricultural soils is only about half that in natural ecosystems. Grasslands, which contain an estimated 40% of the world's arbuscular mycorrhizal biomass, are among the least protected ecosystems and are being converted to farmland four times faster than forests. Less dense fungal networks could reduce the soil's capacity to store carbon and recycle nutrients. Coauthor Merlin Sheldrake called the map an exciting step toward understanding this planetary circulatory system and working with fungi to address challenges like food security and climate change.