A colossal network of arbuscular mycorrhizal (AM) fungi, stretching an estimated 68.35 quadrillion miles, has been mapped beneath the Earth's surface, according to a new study. This extensive fungal web is capable of circling the globe 2.7 trillion times and contains approximately 300 megatonnes of carbon, a weight roughly five times that of all living humans. IMAGE4[Scientists have mapped a vast hidden network of fungi beneath our feet, which could stretch 2.7 trillion times around the Earth "Scientists have mapped a vast hidden network of fungi beneath our feet, which could stretch 2.7 trillion times around the Earth"]
These microscopic threads, known as hyphae, are found in nearly every terrestrial environment, from soil surfaces to depths of up to 26 feet. AM fungi form symbiotic relationships with an estimated 70 percent of all plant species, facilitating the exchange of essential nutrients like nitrogen and phosphorus for carbon. Plants rely on these fungal partnerships for up to 80 percent of their phosphorus and 20 percent of their nitrogen. IMAGE6[Researchers found that the network contains approximately 300 megatonnes of carbon - about five times the weight of all living humans on Earth put together "Researchers found that the network contains approximately 300 megatonnes of carbon - about five times the weight of all living humans on Earth put together"]
The research, led by Dr. Justin Stewart of the Society for the Protection of Underground Networks (SPUN), involved analyzing over 1,600 soil samples from 4,000 global sites. Machine learning models were then trained using this data, alongside information on climate, soil chemistry, and vegetation, to predict fungal density across different ecosystems. The study also utilized a robotic imaging system to measure the radius of hyphae strands, allowing for a calculation of the network's total biomass.
Dr. Stewart described the fungal network as akin to a vast underground "transport infrastructure," comparable to road networks above ground, which moves carbon and nutrients to support life. The findings indicate that farmland soils exhibit roughly half the mycorrhizal density of wild ecosystems. Wild grasslands, such as those found on the Tibetan Plateau, harbor a significant portion of the world's AM fungi, yet these areas are among the least protected ecosystems, being converted to agricultural land at a faster rate than woodlands. IMAGE5[Grasslands such as the Tibetan Plateau are home to 40 per cent of the world's AM fungi, despite being some of the least protected ecosystems on Earth "Grasslands such as the Tibetan Plateau are home to 40 per cent of the world's AM fungi, despite being some of the least protected ecosystems on Earth"]
Experts warn that degradation or loss of this fungal network could have severe consequences for terrestrial ecosystems. Dr. Toby Kiers, executive director of SPUN, highlighted that these fungi are fundamental to ecosystem resilience. Without them, soils may lose their capacity to recover, making above-ground vegetation more vulnerable.
Arbuscular mycorrhizal fungi are ancient organisms primarily composed of thread-like hyphae that permeate the soil. They are distinct from plants and do not photosynthesize. Their role in the ecosystem extends to carbon sequestration, with estimates suggesting they absorb around four billion tonnes of carbon dioxide annually. IMAGE3[Stretched end to end, these complex networks would cover the distance from the Earth to the sun over one billion times over "Stretched end to end, these complex networks would cover the distance from the Earth to the sun over one billion times over"]