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A billion-times hidden web
Scientists have mapped a global underground network of arbuscular mycorrhizal fungi stretching an estimated 110 quadrillion kilometres across Earth’s topsoil, a distance described as nearly a billion times the distance to the Sun.
“Hidden underground around the world lie 110 quadrillion kilometers of arbuscular mycorrhizal fungal networks—webs of ultra-thin threads that, if connected in a single line, would stretch almost a billion times the distance between the Earth and the sun, according to new research published in Science on Thursday”
The work, published in Science on Thursday, June 11, used more than 16,000 soil samples and machine-learning models to build what Le Monde calls the first global map of these networks’ scale.
The study estimates that Earth’s topsoils contain approximately 300 megatons of carbon locked inside these fungal networks, and it reports that the fungi form symbiotic relationships with 70% of land plant species.
Researchers say the networks are made of hyphae—microscopic fungal threads that collectively stretch through the world’s soils—and that they support plant growth and ecosystem health by helping plants absorb water and essential nutrients such as phosphorus and nitrogen.
The Times of India frames the discovery through a comparison to Andy Weir’s science-fiction novel Project Hail Mary, noting that the fungi are not alien organisms and do not behave like Astrophage.
Voices on scale and method
Inside Climate News quotes Toby Kiers saying, "This is the moment where we went from knowing that this system exists to really knowing where it is, how dense it is and where it’s been," as the study estimates distribution and mass using soil samples, machine learning, and laboratory testing.
EurekAlert! adds that the research produced first global maps estimating the distribution and mass of Earth’s arbuscular mycorrhizal fungal networks, and it says the work includes an interactive visualization to show where the systems are thriving and where they are threatened.
The mapping effort is grounded in data from over 16,000 soil cores and uses machine-learning models to predict network density in unsampled ecosystems, with calibration tied to robotic imaging of over 300,000 living AM fungal hyphae grown in the lab.
EurekAlert! reports that grassland ecosystems are home to an estimated ~40% of Earth’s arbuscular mycorrhizal fungal infrastructure, and it identifies the flooded grasslands of South Sudan, the Everglades in Florida, and the Tibetan plateau as exceptionally high predicted network density.
The study also quantifies a carbon pathway, estimating that AM fungal networks transport an estimated ~4 billion tons of CO2e into soils each year, equivalent to 11% of all human-related carbon-dioxide emissions.
What’s at risk next
The Guardian reports that the study documents potential threats, finding that network densities in cropland are 47.3% lower than in wild ecosystems, and it quotes Justin Stewart saying, "A lot of large-scale agriculture practices harm fungal networks."
“Even if you don’t like eating mushrooms, you’re in debt to fungi”
The same Guardian account says tilling can "literally rip it up," while fertilisers or fungicides can disrupt the symbiosis between plants and the fungi.
It warns that lower-density fungal networks reduce the soil’s ability to store carbon and distribute nutrients, and it says the networks also protect waterways from nitrogen, phosphorus and other chemicals.
Le Monde reports that the international team compiled data from 322 studies, analyzing more than 16,000 soil cores from nine major global ecosystems (biomes) and developing machine-learning models to reveal the networks’ colossal scale.
The Guardian concludes by saying the researchers plan to present the data to governments at the upcoming desertification Cop in Mongolia in August, framing the dataset as a way to understand where fungal systems are thriving and where they are threatened.
