Scientists Map Hidden Fungal Networks Storing Carbon

Beneath every step you take, an invisible web of life is quietly saving the planet.

Scientists just mapped the world's mycorrhizal fungal networks for the first time, revealing an underground system so vast it would stretch to the sun and back nearly a billion times. The Society for the Protection of Underground Networks and collaborators published their findings in Science, giving us our first clear picture of where these vital threads exist and how much carbon they store.

The numbers are staggering. A single teaspoon of healthy soil can contain up to 10 meters of living fungal network. Globally, these microscopic threads capture and store an estimated 4 billion tons of CO2 equivalent annually, roughly 11% of all human-related emissions.

The team analyzed more than 16,000 soil samples from nine different ecosystems worldwide. They used machine learning to predict network density in areas they couldn't physically sample, then confirmed their models by imaging over 300,000 individual fungal threads in laboratory conditions.

Their interactive Mycorrhizal Infrastructure Map now shows density estimates for every square kilometer of land on Earth. Anyone can zoom in to see the fungal infrastructure beneath their own community.

The maps reveal surprising patterns. Grasslands hold 40% of Earth's total arbuscular mycorrhizal fungal biomass, with especially dense networks in South Sudan's flooded grasslands, Florida's Everglades, and the Tibetan Plateau. These fungi partner with nearly all land plants, trading water and nutrients for carbon made from sunlight.

Croplands tell a different story. Farmland soils contain roughly half the fungal density of wild ecosystems, potentially reducing their ability to store carbon and cycle nutrients. The researchers say more work is needed to understand exactly which farming practices protect or harm these underground partners.

The Ripple Effect

This map arrives at a critical moment. Previous research found that 90% of fungal biodiversity hotspots sit outside protected areas, leaving them vulnerable to development and destruction. Now conservationists and policymakers can see not just where diverse fungal species live, but where the densest networks exist.

The implications stretch beyond carbon storage. These fungal networks form a living circulatory system that keeps ecosystems healthy, helping plants access water during droughts and nutrients from deep in the soil. Protecting them means protecting the foundation that supports forests, grasslands, and food systems.

Lead author Justin Stewart and executive director Toby Kiers both emphasize that fungi have been overlooked in climate and conservation planning for too long. Their new map gives decision makers the tool they need to change that, showing exactly where to prioritize protection efforts.

The invisible world beneath our feet just became visible, and it's working harder for the planet than we ever imagined.