Scientists have mapped Earth’s vast underground fungal networks for the first time, revealing a staggering 68 quadrillion miles of fungal threads that help regulate the climate. A groundbreaking new study estimates that arbuscular mycorrhizal fungi form an underground network stretching roughly 110 quadrillion kilometers (68 quadrillion miles), equivalent to nearly a billion times the distance from Earth to the Sun. These microscopic fungal threads create symbiotic relationships with over 70% of land plants, exchanging nutrients and water for carbon while locking away massive amounts of CO₂ in the soil. The research, led by the Society for the Protection of Underground Networks (SPUN), used machine learning models trained on data from more than 16,000 global soil cores, combined with high-resolution robotic imaging of fungal hyphae. However, these critical networks face a serious threat from modern industrial agriculture. Fungal density in croplands is nearly 50% lower than in undisturbed ecosystems, largely due to tilling, chemical fertilizers, and fungicides. This loss reduces the soil’s ability to store carbon, weakens nutrient cycling, and increases chemical runoff. The findings underscore the urgent need to protect these hidden ecosystems. Researchers plan to present the data at the upcoming UN desertification summit to push for global conservation benchmarks. [Stewart, J. D., et al. (2026). Global density and biomass of arbuscular mycorrhizal fungal networks. Science. DOI: 10.1126/science.adu4373]