The World’s Largest Living Network Is Beneath Your Feet — And It’s Made of Fungi
Most of us think of mushrooms as the fruiting bodies that pop up after rain. But the mushroom itself is only the visible tip of something much bigger.
Hidden beneath forests, grasslands and even your garden lies one of the largest living systems on Earth: vast underground fungal networks that quietly support life above ground.
A new study published in Ciencia has revealed just how enormous these networks really are. Researchers estimate that the fine fungal threads woven through the world’s soils stretch for an astonishing 110 quadrillion kilometres. That’s enough to travel from Earth to the Sun almost 750 million times.
It’s an almost impossible number to picture, but it highlights something scientists have known for years: fungi aren’t just part of ecosystems — they’re helping hold them together.
Meet the Underground Network Keeping Plants Alive
The stars of the new research are arbuscular mycorrhizal fungi, a group of fungi that have been partnering with plants for roughly 475 million years.
These fungi form microscopic threads called hifas, which spread through the soil searching for water and nutrients. When a hypha reaches a plant root, the two begin an extraordinary partnership.
The fungus supplies the plant with essential minerals like phosphorus and nitrogen, along with water that might otherwise be out of reach. In return, the plant shares sugars made during photosynthesis.
It’s one of nature’s oldest trade agreements. And, one of its most successful.
Today, scientists estimate that more than 70% of all plant species rely on these fungal partnerships. Without them, many forests, grasslands and agricultural systems would look very different.
The Internet Beneath Our Feet
Mycelial networks are often compared to the internet, and while the analogy isn’t perfect, it helps explain how remarkable they are.
A single fungus doesn’t grow as one solid organism. Instead, it spreads as an intricate web of branching hyphae, continuously exploring the soil around it. These microscopic threads can fuse together, reroute resources around damaged areas, and connect with the roots of multiple plants simultaneously.
Research over the past few decades has shown that these networks don’t simply transport nutrients. They can also move water, carbon and chemical signals between connected plants.
For example, when one plant is attacked by insects or disease, chemical warning signals can sometimes travel through fungal networks, allowing neighbouring plants to activate their own defence systems before they’re attacked. Scientists are still exploring exactly how widespread this communication is, but there’s growing evidence that mycorrhizal networks play an important role in helping ecosystems respond to environmental stress.
Rather than thinking of plants as isolated individuals, many ecologists now view forests and grasslands as highly interconnected communities linked by fungal infrastructure beneath the soil.
The First Global Map of Earth’s Fungal Highways
Despite their importance, surprisingly little has been known about where these fungal networks are most abundant.
That’s one of the reasons researchers founded the Society for the Protection of Underground Networks (SPUN) in 2021. The organisation brings together scientists from around the world to better understand—and ultimately protect—the planet’s hidden fungal ecosystems.
In the new study, researchers combined machine-learning models with data collected from more than 16,000 soil cores gathered across the globe. The result is the first global map of arbuscular mycorrhizal fungal networks.
Their calculations were staggering. If every hypha identified by the researchers were placed end to end, the network would extend for 110 quadrillion kilometres.
To put that another way, it could stretch from Earth to the Sun almost 750 million times. Even a tiny amount of soil contains astonishing amounts of fungal life.
“There could be up to 10 metres (32ft) of mycorrhizal network in just a teaspoon of soil,” said Dr Justin Stewart, lead author of the study.
Why These Fungi Matter for the Climate
The importance of these underground networks goes far beyond healthy plants.
As fungi receive carbon-rich sugars from plants, some of that carbon becomes incorporated into the soil rather than returning immediately to the atmosphere. Healthy fungal networks therefore help lock carbon underground, making them an important (if often overlooked) part of Earth’s carbon cycle.
These fungi also improve soil structure, help retain water during droughts and make nutrients available more efficiently. In other words, they’re quietly supporting agriculture, biodiversity and climate regulation all at once.
Scientists increasingly see healthy soils as one of our strongest natural allies against climate change, and fungi are central to keeping those soils functioning.
Modern Agriculture Is Breaking the Network
The study also identified a worrying trend. On average, fungal network density in croplands was found to be 47.3% lower than in nearby natural ecosystems.
According to the researchers, many modern farming practices unintentionally damage underground fungal communities.
“A lot of large-scale agriculture practices harm fungal networks,” Stewart explained. “The most apparent way is with something like tilling, where you go into a soil and literally rip it up.”
Heavy use of fertilisers and fungicides can also interfere with the close relationship between fungi and plant roots.
If crops receive nutrients directly from synthetic fertilisers, they have less incentive to invest energy into maintaining fungal partnerships, weakening these ancient symbiotic relationships over time.
Healthy Fungi Mean Healthier Ecosystems
The consequences extend well beyond farmland. Dense fungal networks help prevent excess nitrogen and phosphorus from washing into rivers and lakes, improving water quality while supporting healthier soils.
If those networks disappear, those natural filtration systems weaken too.
“If they disappear, there’s going to be a lot more chemicals going into waterways,” said Dr Toby Kiers, one of the study’s authors.
Kiers described the project as “one of the most exciting” of her career.
She says the ultimate goal is to help governments understand where fungal ecosystems are thriving and where they need protection. The research team plans to present its findings to policymakers at the upcoming UN Desertification COP in Mongolia.
The World’s Fungal Hotspots
The new global map also revealed where underground fungal life is most abundant. Grasslands emerged as some of the richest ecosystems on Earth for mycorrhizal fungi.
The researchers found exceptionally dense fungal networks beneath places including Florida’s Everglades, the vast Sudd wetlands of South Sudan, and prairie and steppe grasslands around the world.
Ironically, many of these ecosystems remain poorly protected and are increasingly threatened by agricultural expansion, land degradation and climate change.
Working With Fungi Instead of Against Them
The researchers believe farming doesn’t have to come at the expense of fungal life. Instead, they argue agriculture could benefit enormously from working alongside these underground partners.
Practices such as reducing soil disturbance, planting cover crops and encouraging healthy fungal communities may help crops access nutrients naturally, reducing reliance on synthetic fertilisers while simultaneously increasing carbon storage in soils.
As Kiers explains, conservation is increasingly moving below ground as well as above it.
“There’s a big movement now to not only restore communities above ground, the things that you can see, the plants and animals, but also to restore underground fungal communities. And this dataset allows us to have benchmarks for what a healthy microbial community can look like.”
It’s a shift in perspective that’s long overdue.
Seeing Fungi in a New Light
Fungi have often been overlooked compared with plants and animals, but that’s beginning to change.
Researchers are uncovering their role in everything from ecosystem resilience and carbon cycling to sustainable agriculture and biodiversity. At the same time, growing interest in mushrooms (including psilocybin-containing species) is encouraging more people to appreciate fungi as some of the most remarkable organisms on Earth.
Dr Merlin Sheldrake, biologist and co-author of the study, believes this research is about more than simply mapping fungal networks.
It helps us discover “ways that we can better work with fungi to help address many of the unfolding challenges of our times, from food security to climate change.”
The more we learn about life beneath our feet, the clearer one thing becomes. The real magic of mushrooms isn’t only found above ground.
It’s hidden in the vast living networks below us, quietly connecting plants, storing carbon and helping keep our planet alive — one microscopic thread at a time.
