Threads of underground fungal networks are long enough to reach beyond the Solar System

Text settings Story text Size Small Standard Large Width * Standard Wide Links Standard Orange * Subscribers only   Learn more Minimize to nav 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. These fungal communities form intimate relationships with the roots of plants, which they provide with nutrients like phosphorus and nitrogen in exchange for carbon, 1 billion tons of which the networks sequester underground annually, previous research has found. If the fungal network wasn’t storing it, that carbon would be warming the atmosphere. But those networks have never been mapped globally until now. The new study led , or SPUN, an organization founded to map mycorrhizal fungi networks, used a combination of literature review, soil samples from around the globe, machine learning and laboratory testing to estimate the distribution and mass of these systems and map where they are densest. “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,” said Toby Kiers, executive director and co-founder of SPUN and a co-author of the study. For decades, researchers have known arbuscular mycorrhizal fungi form intimate symbiotic relationships with roughly 80 percent of the globe’s plant species and are found nearly everywhere plants are. But the extent of those networks and where they are densest, such as grasslands, and where they are being lost, like in agricultural areas, hasn’t been well understood until now. “[The study] helps us come to grips with how important these below ground organisms can be to everything that we see above ground,” said James Bever, a professor of ecology and evolutionary biology at the University of Kansas who studies the interactions between plants and microbes like fungi in soils but was not involved in the new study. Justin Stewart, an evolutionary ecologist at SPUN and lead author of the study, said previous studies the team had done on biodiversity of fungi were similar to asking someone to describe the forest outside their home. “They could say ‘well there are three tree species in it.’ That’s great. That tells me about the biodiversity,” he said. “But you don’t actually know how big the forest is, how far apart the trees are.