Scientists just mapped 110 quadrillion kilometers of hidden fungal threads underground, weighing about five times all humans combined

If you’ve ever walked through a Florida wetland or driven past a Midwestern cornfield, you’ve been standing on top of something nearly impossible to imagine. According to a new study published in Science by an international team of researchers including scientists from VU Amsterdam and the Society for the Protection of Underground Networks (SPUN), nearly every patch of soil on Earth contains a sprawling web of fungal threads so long that, laid end to end, it would stretch from Earth to the sun almost a billion times over.

After decades without a global picture of these networks, this is the moment scientists went from just knowing this system exists to actually knowing where it lives and how dense it is, according to Toby Kiers, SPUN’s executive director and a co-author of the study.

Numbers too large to imagine
This is a difficult scale to process. The study found that there are about 110 quadrillion kilometers of these threads, called hyphae, in global topsoils, each finer than a human hair, and that they weigh between four and six times the total weight of all humans alive today. According to National Geographic's coverage of the findings, every square centimeter of soil in just the top 15 centimeters of soil contains about 4.4 meters of hyphae, roughly 50 times longer than the fine roots of the plants the fungi partner with. According to lead author Justin Stewart, there could be up to 10 meters of this fungal network curled up in a single teaspoon of soil. Previous fungal research was like trying to describe a forest by counting the number of tree species, but never measuring how big the forest actually was, Stewart said. That’s what this mapping work, based on 16,000 soil samples and robotic lab imaging, was designed to close the gap on.

Right under America's wetlands, prairies, and deserts
This isn’t some distant phenomenon. Some of the most concentrated fungal networks on Earth are located in places American readers would recognize, the study's map reveals, including the flooded grasslands of the Everglades in Florida, along with similar wet terrain in South Sudan and the Tibetan plateau. According to Inside Climate News's reporting on the study, deserts in the American Southwest remain among the least-studied ecosystems for these networks, leaving a real gap in understanding how they work in arid US landscapes. According to the same Science study, wherever there’s a thriving plant community, these fungi are almost certainly trading phosphorus and nitrogen for the sugars plants produce through photosynthesis. This can expand a plant’s nutrient-foraging reach by up to 100 times, and cover more than 80 percent of its phosphorus needs. According to Stewart's comments to National Geographic, this partnership between plants and fungi dates back roughly 450 million years, making it one of the oldest cooperative relationships in the natural world.

An unsung carbon vault beneath every backyard
These networks don’t just feed plants; they also suck carbon dioxide from the air and bury it underground. The study estimates that these fungi transport about 4 billion tons of carbon dioxide equivalent into soil each year, nearly 11 percent of all human-caused CO2 emissions each year. According to James Bever, a professor of ecology and evolutionary biology at the University of Kansas who wasn't involved in the research but spoke to Inside Climate News, this kind of mapping helps explain how important these underground organisms are to everything above ground.

Farming is quietly squeezing this lifeline
That subterranean carbon vault is not invulnerable. The study found that croplands have about half the density of fungal networks as wild ecosystems do, and that wild grasslands alone contain an estimated 40 percent of the world’s fungal biomass, even as they disappear rapidly. Grasslands and wetlands worldwide are being turned into cropland and pasture at almost four times the rate forests are cleared, largely to satisfy the global appetite for food, animal feed and biofuels, according to a study in the Proceedings of the National Academy of Sciences.

Almost none of it is protected, and nobody has a fix yet
Most of these fungal networks lack legal protection. A 2025 study published in Nature finds that more than 90 percent of the planet's mycorrhizal fungal biodiversity hotspots are not within any protected area. According to Corentin Bisot, an AMOLF biophysicist and study co-author who spoke to Inside Climate News, scientists still don't have the practical toolbox to help grow more fungi in a specific grassland even if they wanted to. According to Inside Climate News, the SPUN researchers plan to present these findings to policymakers at the United Nations climate conference this year, with hopes that the data will finally earn fungi a place in global climate strategy. For now, researchers say, there’s a lot more going on under our feet than almost anyone knew, and protecting it may be as urgent as protecting the forests and oceans above it.