A new study published in the journal Science has produced the first global maps showing the distribution, density, and estimated mass of arbuscular mycorrhizal fungal networks, revealing the enormous scale of one of Earth’s most important yet largely invisible ecosystems. These underground fungal networks play a critical role in supporting plant life, cycling nutrients, and helping regulate the global climate by storing carbon in soils.
Arbuscular fungi form mutually beneficial relationships with approximately 70% of the world’s plant species. In these partnerships, plants provide carbon produced through photosynthesis, while the fungi supply water and essential nutrients such as phosphorus. Because of their ability to connect plants and transport resources underground, mycorrhizal fungi are often described as a living circulatory system for terrestrial ecosystems.
To create the first global assessment of these networks, researchers collected and analyzed data from more than 16,000 soil cores gathered from ecosystems around the world, including forests, grasslands, deserts, and tundra. Using machine-learning models, they combined field observations with environmental data to estimate fungal network density in regions where direct measurements were unavailable. The team also collaborated with the AMOLF Biophysics Institute in Amsterdam, where robotic imaging systems analyzed more than 300,000 living fungal structures to improve the accuracy of the models.
The results reveal an astonishing underground infrastructure. Scientists estimate that arbuscular fungal networks collectively stretch for approximately 110 quadrillion kilometers beneath Earth’s surface. They also estimate that these networks contain around 300 megatons of carbon, making their total biomass roughly four to six times greater than the mass of all living humans. Researchers noted that a single teaspoon of healthy soil may contain up to 10 meters of fungal network.
The study highlights the crucial ecological functions of mycorrhizal fungi. In healthy soils, these networks can increase the effective foraging area of plant roots by as much as 100 times and provide more than 80% of the phosphorus required by many plants. By moving carbon, water, and nutrients through ecosystems, they help sustain plant productivity, biodiversity, and long-term soil health. Previous research has also shown that these underground transport systems move carbon and nutrients with remarkable efficiency, creating highly effective biological supply chains beneath the surface.
Alongside the scientific findings, researchers developed the Mycorrhizal Infrastructure Map, an interactive visualization that estimates fungal network density for every square kilometer of terrestrial land where sufficient data are available. The tool provides governments, scientists, and conservation organizations with a new way to monitor and protect underground ecosystems that have historically been overlooked.
The study also identified significant threats to these networks. Densities of mycorrhizal fungi in agricultural croplands are predicted to be roughly half those found in natural ecosystems. Grasslands, which contain an estimated 40% of the world’s arbuscular fungal biomass, are particularly vulnerable because they are being converted to farmland at a rate four times faster than forests. Previous research further found that 95% of biodiversity hotspots for these fungi lie outside protected areas.
Researchers emphasize that mycorrhizal fungi have shaped life on Earth for hundreds of millions of years, yet their global distribution and ecological importance remain poorly understood. The new maps provide an important foundation for future research while identifying major gaps in current sampling efforts. Scientists believe a better understanding of these underground networks could help address challenges related to climate change, biodiversity conservation, soil restoration, and global food security.
https://phys.org/news/2026-06-global-mycorrhizal-fungi-reveals-true.html