A living web runs through the soil beneath forests, prairies, marshes, and croplands, linking plants to fungal partners that help feed them, move water, and pull carbon underground. Until now, no one had mapped that web at the scale of the planet. The new analysis, published in Science, offers the first global estimate of the physical reach of arbuscular mycorrhizal fungal networks. This is one of the most widespread partnerships in nature. The researchers calculate that the top 15 centimeters of Earth’s soils hold about 110 quadrillion kilometers of these fungal filaments, known as hyphae, and roughly 300 megatons of carbon in living fungal biomass. “It is hard to overstate the importance and enormity of these fungi,” said lead author Dr. Justin Stewart of the Society for the Protection of Underground Networks, or SPUN. “There could be up to 10 meters (32 feet) of mycorrhizal network in just a teaspoon of soil.” The numbers point to an unseen system that helps support much of life on land. Arbuscular mycorrhizal, or AM, fungi form symbiotic partnerships …