Researchers have mapped Earth's underground fungal networks, revealing threads of arbuscular mycorrhizal fungi that collectively span distances exceeding the Solar System's reach. The study, led by Stewart and colleagues, focuses specifically on living fungal networks while acknowledging dead networks also contribute significantly to carbon storage and ecosystem biomass.

Croplands show fungal network densities at just 50 percent of wild ecosystems, with grasslands containing 40 percent of the world's arbuscular mycorrhizal biomass. However, these vital grasslands face intense pressure — they're converted to farmland four times faster than forests, despite being among Earth's least protected ecosystems.

SPUN's previous research indicates 90 percent of global fungal communities lack protection, while understudied regions like the American Southwest deserts remain poorly understood. The team will present findings at COP31 to advocate for fungal network preservation in climate policy discussions.

Co-author Corentin Bisot notes researchers lack the tools to restore fungal networks even in adjacent grasslands. Stewart emphasizes this mapping represents only the beginning — like early Spanish cartography of California, future discoveries will refine our understanding of these critical underground systems that support plant life and carbon sequestration.