Scientists have created the first global map of mycorrhizal fungi, the microscopic filaments that form vast underground networks connecting plant roots and cycling nutrients and carbon through soil. These fungi, which have partnered with plants for over 400 million years, are invisible to the naked eye but immense in scale—researchers estimate 68 quadrillion miles of fungal threads across Earth, equivalent to 730 million times the distance from Earth to the sun. Using soil samples, satellite data, and AI, the team mapped where these networks are densest, including wetlands like the Everglades and unexpected hotspots in grasslands, which are often overlooked in conservation efforts compared to forests.

The mapping project, led by ecologist Justin Stewart and researchers with the Society for the Protection of Underground Networks, aims to bring visibility to a critical but hidden part of Earth's ecosystem. Fungi trade nutrients like nitrogen and phosphorus with plants in exchange for carbon from photosynthesis, then sequester that carbon deep in the soil—playing a major role in climate regulation. Despite their importance, these networks remain vulnerable to land-use changes, agriculture, and desertification.

The discovery underscores a growing realization: you can't protect what you don't know. By revealing where fungal networks thrive and where they're sparse—such as in deserts like the Sahara—this research provides a baseline for future conservation strategies. The findings also challenge assumptions about which ecosystems deserve protection, highlighting grasslands as unexpectedly vital underground hubs.