The first global map of underground fungal networks reveals the colossal scale of their presence on the planet.
Earth’s underground fungal network is so vast that if it were in outer space and laid out in a straight line, it would cover about 10% of the Milky Wayconcludes a new one , published this Thursday in the magazine Science.
These underground structures, called fungal networks arbuscular mycorrhizalwork in partnership with most of the world’s land plants, providing them with nitrogen and phosphorus in exchange for carbon.
Now, the first of this fungal network has revealed where its intricate branching structures are most densely concentrated.
In high-elevation prairies or flooded prairies, such as the Florida Everglades, the top 6 inches of soil are especially dense, concentrating about 40% of global fungal biomass.
According to the researchers, this data shows that intact prairies are an essential and reliable carbon reservoir.
“This is the densest fungal forest on Earthand it’s under wild prairies,” he told Justin Stewartfirst author of the study and an evolutionary biologist at the Society for the Protection of Underground Networks (SPUN), a scientific organization dedicated to the study of fungi that establish symbiotic relationships with plants. “It’s changing the way we discuss distribution of life on Earth”.
“I hope this contributes to the discussion about their protection, because wild prairies are disappearing very quickly,” Stewart added. “These are areas that people are really destroyingbecause it is much easier to uproot grass than to uproot a tree.”
The map revealed, for example, that some agricultural practicess are decimating this underground network: on average, the surface layer of agricultural soils has densities of around 50% lower.
The hidden fungal forest
Arbuscular mycorrhizal fungi are made up of tiny branched filaments called hyphae. These hyphae networks function as channels of two-way circulationtransporting nutrients to plants and carbon from them.
As a result, fungi absorb enormous amounts of carbon. One estimate pointed to around 3.9 billion metric tons of carbon dioxide equivalent per year, which corresponds to around 11% of emissions from fossil fuels in 2021.
Although these fungi are essential to the health of the Earthit was not known how they were distributed across the planet. “It’s like saying that we know that every day 100 million cars circulate on Earth, but We have no idea what road network allows this circulation”, compared Stewart.
To construct the first global map of the distribution and density of hyphal networks, Stewart and his colleagues gathered data from 16,669 samples of solo collected in 322 previous studies. These samples provided information on hyphal density, both in field studies and in pot experiments, with field samples coming from all continents and nine biomes.
The team then used artificial intelligence to predict the distribution of fungi arbuscular mycorrhizal infections in every square kilometer of topsoil on a global scale, based on data on climate, soil chemistry, vegetation and hyphal density.
The researchers concluded that the average density of hyphae in the surface layer of terrestrial soils is 4.4 meters per cubic centimeter.
If all the hyphae were arranged in a straight line, they estimate that they would extend for about 110 thousand billion kilometers. This is equivalent to almost a billion times the distance between the Earth and the Sun, or about 10% of the width of the Milky Way.
As wild prairies had the highest densitywith 6.6 meters per cubic centimeter, while areas of cultivated trees recorded the lowest density, with 3.8 meters per cubic centimeter.
Although the team was unable to identify which agricultural practices had the greatest impact on hyphal density, the authors wrote in the study that fungicides and fertilizers based on phosphorus and nitrogen may help explain the lower presence of these structures in the surface layer of agricultural soils.
“This seminal investigation makes visible a part of the invisible”, told Live Science Edward the Evangelista plant scientist at the Université Côte d’Azur in France, who was not involved in the study.
The map is an “important landmark”stated Evangelisti, and paves the way for the study of the functional importance of these gigantic underground networks, for example in drought tolerance and disease resistance. The dynamic nature of these fungi will also need to be investigated.
“The abundance of live hyphae is important, but for the carbon cycle, we also need to know how fast do these hyphae grow?they die and contribute to stable carbon in the soil”, he concluded.
