An international team of researchers has, for the first time, created a global map of arbuscular mycorrhizal fungi — one of Earth's most important and at the same time most invisible ecosystems. These fungi exist as microscopic threads, or hyphae, that form a fungal network. In exchange for help obtaining nitrogen and phosphorus, they receive carbon from plants produced during photosynthesis.
To create the map, the researchers analyzed more than 16,000 soil samples from all continents. Artificial intelligence then matched data on climate, soil types, and vegetation and built a model of how the fungal network is distributed across the planet. It found that, on average, the top layer of soil contains about 4.4 meters of fungal threads per cubic centimeter.
The highest fungal-network density was found in undisturbed natural grasslands, wetlands, and high-altitude regions. Such areas contain up to 40% of the global biomass of these fungi. According to the researchers' estimates, the underground network annually accumulates about 3.9 billion tons of carbon dioxide equivalent, playing an important role in Earth's carbon cycle.
Conditions on agricultural land are noticeably different: the density of mycorrhizal fungi is about twice as low as in the wild. The researchers link this to intensive tillage, the use of chemical crop protection products, and excess fertilizers.
In recent years, climate policy has focused mainly on forests as the main natural carbon sinks. The new map shows that wild grasslands and herbaceous ecosystems may play an equally important role. The new map will help conserve biodiversity more effectively, protect key ecosystems, and account for the role of grassland areas in the fight against climate change.
