Scientists have published the first global map of arbuscular mycorrhizal fungi, the underground network that connects about 70 percent of Earth's plants. The study in Science estimates the fungal web holds roughly 300 megatons of carbon, equivalent to four to six times the carbon stored in all living humans. The network acts as a natural carbon sink, moving and storing carbon underground each year and helping regulate the climate. The map, built from over 16,000 soil samples and machine learning models, shows the densest fungal activity occurs beneath grasslands, wetlands, and prairies rather than forests. Croplands have about half the fungal density of wild ecosystems, and grasslands that hold 40 percent of global fungal biomass are disappearing due to development. This raises questions about how land use change affects natural carbon storage capacity.
