Global map of Earth’s mycorrhizal fungal networks could help protect them – Image for illustrative purposes only (Image credits: Unsplash)
Hidden beneath the surface lies a vast web of fungal threads that stretches across the planet’s soils. Researchers have now produced the first global maps showing where these arbuscular mycorrhizal networks are concentrated and how much biomass they contain. The work draws on thousands of soil samples and machine-learning models to reveal patterns that were previously invisible.
The Sheer Scale of the Underground Web
Scientists estimate that the total length of these living fungal threads reaches roughly 110 quadrillion kilometers. If laid end to end, that distance would equal nearly a billion round trips between Earth and the sun. In a single teaspoon of soil, the networks can extend up to 10 meters, according to lead author Justin Stewart of the Society for the Protection of Underground Networks.
The mapping effort focused on arbuscular mycorrhizal fungi, which form partnerships with nearly all land plants. These fungi supply water and nutrients in exchange for carbon produced through photosynthesis. The new density and biomass maps cover nine major biomes and highlight how the networks vary across different environments.
How Researchers Built the Global Maps
The team compiled data from more than 16,000 soil cores drawn from 322 published studies. Machine-learning models then predicted network density and biomass in areas without direct samples. The resulting maps show both the distribution and the total amount of fungal infrastructure present in soils worldwide.
This builds on earlier work published last year in Nature that examined diversity patterns and introduced the Underground Atlas for conservation planning. The current study shifts attention to quantity and location, providing a clearer picture of the physical extent of these networks.
Carbon Movement and Ecological Importance
The networks function as a planetary circulatory system, transferring an estimated 4 billion tons of CO2 equivalent into soils each year. That figure represents roughly 11 percent of global human-related emissions. The maps help identify regions where this underground infrastructure is most dense and potentially most vulnerable.
Because the fungi depend on plant partners, changes in vegetation or land use can affect network extent. The new visualizations offer a tool for understanding these connections at a planetary scale.
Key measurements from the study
- Total estimated length of fungal threads: 110 quadrillion kilometers
- Maximum length in one teaspoon of soil: up to 10 meters
- Annual carbon transfer into soils: 4 billion tons CO2 equivalent
- Share of human-related emissions moved underground: about 11 percent
The maps mark an important step toward recognizing the full extent of life beneath the surface. Further work will be needed to refine predictions in under-sampled regions and to track how networks respond to environmental change over time.
