Fungi are living below your feet. Roughly 110 quadrillion kilometers of living fungal threads are woven through the world’s soils. Stretched end-to-end they would cover a distance nearly a billion times that from Earth to the sun. Now, scientists have mapped where those networks are, how dense they are, and what threatens them.
Last year, researchers published global analyses in Nature about the diversity patterns of underground mycorrhizal fungal communities along with the Underground Atlas to help decision makers visualize where to prioritize conservation.
Now, they ask the question: How much fungal infrastructure exists, and where?
A new study published in Science by researchers with the Society for the Protection of Underground Networks (SPUN) and collaborators produced the first global maps of arbuscular mycorrhizal (AM) fungal network density and biomass.
“There could be up to 10 meters (32 feet) of mycorrhizal network in just a teaspoon of soil,” lead author Justin Stewart of SPUN said in a press statement.
Nearly all land plants live in partnership with arbuscular mycorrhizal fungi. The fungi exchange water and nutrients for carbon made from sunlight. These underground networks act as a living circulatory system for the planet, and the new study found they move an estimated 4 billion tons of CO2 equivalent into soils annually, roughly 11% of global human-related emissions.
To build the density maps, the team drew on data from more than 16,000 soil cores collected across nine biomes referenced in 322 published studies. They developed machine-learning models to predict network density in unsampled regions, then calibrated those predictions using robotic imaging of more than 300,000 individual living hyphae (the tubular cells that make up fungal networks) grown under laboratory conditions at the Amsterdam research institute AMOLF.
The researchers visualized their results in a new interactive tool called the Mycorrhizal Infrastructure Map with estimates calculated for every square kilometer of terrestrial land. The maps reveal striking geographic variation.
Grassland ecosystems harbor an estimated 40% of all AM fungal biomass on Earth, with especially dense networks in South Sudan’s flooded grasslands, Florida’s Everglades in the U.S., and the Tibetan Plateau in Asia.
Croplands had roughly half the fungal network density of wild ecosystems. While researchers say more work is needed to link specific farming practices to fungal health, less dense networks may diminish soils’ ability to store carbon and cycle nutrients.
Previous research found that 90% of AM fungal biodiversity hotspots lie outside protected areas. The new data suggest the physical infrastructure of those networks is similarly exposed.
“Fungi have been ignored in climate and conservation for too long,” study co-author Toby Kiers, SPUN’s executive director, said. “Now is the time to change that trajectory.”
Banner image: A screenshot from the Mycorrhizal Infrastructure Map.
This story first appeared on Mongabay
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