Underground fungal networks prove crucial for climate, biodiversity, and food security
An international team of researchers has created the first global map of arbuscular mycorrhizal fungi: microscopic fungal networks that collaborate with plant roots underground. The study, published in Science, shows that this hidden infrastructure plays a much larger role in the functioning of ecosystems and carbon sequestration than previously assumed.
The researchers estimate that the topsoil worldwide contains approximately 110 quadrillion kilometers of fungal filaments. “That is nearly a billion times the distance between the Earth and the Sun. These underground networks form an essential transport system for water, nutrients, and carbon, and support an estimated seventy percent of all plant species on Earth,” says first author systems ecologist Justin Stewart of Vrije Universiteit Amsterdam.
Four billion tons of CO₂ equivalent
The study shows that these fungal networks transport approximately four billion tons of CO₂ equivalent to the soil annually. That corresponds to approximately eleven percent of global human-caused CO₂ emissions. Consequently, fungi play an important role in climate regulation and carbon storage.
For the study, scientists analyzed data from more than 16,000 soil samples from around the world. Using machine learning and advanced imaging techniques, they developed the first global maps of the density and distribution of these fungal networks. An interactive visualization was also developed to enable researchers, policymakers, and nature managers to better monitor the condition of subsurface ecosystems.
Fungal infrastructure in grasslands
The results show that grasslands worldwide harbor approximately forty percent of the total fungal infrastructure. The swamp grasslands of South Sudan, the Everglades in Florida, and the Tibetan Plateau, in particular, appear to contain exceptionally high densities of fungal networks. At the same time, grasslands are among the least protected ecosystems in the world and are converted to agricultural land four times faster than forests.
The researchers also identify a potential threat to soil health. In large-scale agricultural areas, fungal networks are expected to be, on average, fifty percent less dense than in natural ecosystems. Although follow-up research is needed to determine the precise influence of agricultural practices, scientists fear that a decline in these networks could reduce soils' ability to store carbon, recycle nutrients, and withstand drought and other stressors.
Including fungi in climate and nature policy
According to the researchers, the results underscore the importance of including fungi in climate and nature policy. Subsurface ecosystems often remain overlooked in nature management and protection, even though they play a fundamental role in biodiversity, food production, and climate regulation.
The new maps reveal where these crucial fungal networks are located, where they are under pressure, and which areas deserve priority for protection. At the same time, the research shows how much remains unknown: large parts of the world have barely been explored. Consequently, this study represents an important step towards a better understanding of the hidden ecosystem beneath our feet and its contribution to a resilient planet.