A vast living infrastructure lies hidden beneath forests, grasslands, farms, and wild landscapes. Arbuscular mycorrhizal fungi attach to plant roots and send threadlike filaments through the soil, helping plants receive nutrients and water while moving carbon underground. These networks are increasingly being recognized as one of the planet’s great biological systems.
New research in Europe used machine learning, a high-resolution imaging robot, and data from more than 16,000 soil samples to estimate the size of this underground web. If laid end to end, the fungal filaments would stretch 68 quadrillion miles. Together they contain roughly 300 megatons of carbon, several times the carbon contained in all human bodies on Earth. The study also found particularly dense fungal networks beneath grasslands, ecosystems that often receive far less conservation attention than forests.
Toby Kiers of Vrije University Amsterdam said the goal is to “shine a light on some of these hidden patterns underground.” The finding changes the way soil should be understood. It is not dead matter or simply a substrate for crops. It is a living, carbon-storing, plant-feeding, climate-regulating network. Protecting it may become central to regenerative agriculture, climate repair, and ecological restoration.