A forest so vast it would stretch one-tenth across the Milky Way
Beneath nearly every continent, an invisible forest of fungal threads has quietly sustained plant life and absorbed billions of tonnes of carbon for hundreds of millions of years — and scientists have now, for the first time, mapped its full global extent. The picture that emerges is one of breathtaking scale and fragility: these mycorrhizal networks sequester carbon equivalent to 11 percent of annual human fossil fuel emissions, yet agricultural expansion is dismantling them at a pace that leaves half their density behind. What the map makes newly visible is an ancient bargain between fungi and plants that civilization has been quietly breaking, one tilled acre at a time.
- The first global map of underground fungal networks has exposed a carbon storage system of planetary consequence — 4.3 billion tonnes of CO2 absorbed annually — that most of humanity never knew existed.
- Agricultural tilling, monoculture farming, and chemical application have already cut fungal density in croplands by roughly half compared to intact natural ecosystems, severing networks that took millennia to form.
- Grasslands and wetlands like the Florida Everglades concentrate nearly 40 percent of Earth's total fungal biomass in just the top 15 centimeters of soil, making their preservation an urgent climate priority.
- With farming practices largely unchanged and agricultural expansion continuing, the planet's most reliable natural carbon sinks are being quietly erased before their full value was even understood.
- Scientists and policymakers now face a clarifying challenge: the map transforms an invisible crisis into a visible one, raising the question of whether soil health will be treated with the same urgency as the forests we can see.
Beneath the soil of nearly every continent lies a fungal forest of staggering scale — threadlike filaments invisible to the eye yet collectively forming one of Earth's most consequential ecosystems. Scientists have now released the first comprehensive global map of these underground mycorrhizal networks, and what it reveals is both wondrous and deeply troubling.
These fungi attach to plant roots in an ancient partnership: they extract nitrogen and phosphorus from the soil and deliver them to plants, which in return send down sugars to feed the fungi. This exchange has sustained terrestrial life for hundreds of millions of years. In certain landscapes — high-altitude grasslands and seasonally flooded wetlands — nearly 40 percent of all fungal biomass on Earth is packed into just the top 15 centimeters of soil. Beyond feeding plants, these networks function as formidable carbon vaults, absorbing roughly 4.3 billion tonnes of CO2 equivalent each year — about 11 percent of all fossil fuel emissions humanity produced in 2021.
The map also tells a darker story. Croplands contain, on average, only half the fungal density of intact natural ecosystems. Tilling, monoculture planting, and chemical use have systematically dismantled networks that took millennia to build. Every acre converted to industrial agriculture represents not merely a change in what grows above ground, but the destruction of an intricate living system regulating both nutrient cycling and carbon storage.
The implications are profound. As agricultural expansion continues without meaningful reform, humanity is simultaneously reducing soils' capacity to nourish plants and eroding one of the planet's most powerful mechanisms for drawing carbon from the atmosphere. The map has made visible what was once only theorized: that the invisible life beneath our feet may matter as much to the planet's future as any forest we have ever thought to protect.
Beneath the grass and soil of nearly every continent lies a forest so immense that if you could unwind it into a single thread, it would stretch across a distance equal to one-tenth the width of the Milky Way. This forest has no trees. It is made entirely of fungi—threadlike filaments so small they are invisible to the naked eye, yet so vast in aggregate that they form one of Earth's most consequential ecosystems.
Scientists have just released the first comprehensive global map of this underground fungal network, and what it reveals is both wondrous and alarming. These microscopic threads, called mycorrhizae, penetrate the soil and attach themselves to plant roots in an ancient partnership. The fungi extract nitrogen and phosphorus from the earth and deliver them to the plants; in return, the plants send down sugars manufactured through photosynthesis, feeding the fungi in a transaction that has sustained terrestrial life for hundreds of millions of years.
The sheer density of this system in certain places is staggering. In grasslands—particularly in high-altitude regions and seasonally flooded wetlands like Florida's Everglades—nearly 40 percent of all fungal biomass on Earth is crammed into just the top 15 centimeters of soil. These underground highways do more than feed plants. They are among the planet's most efficient carbon vaults. The fungi absorb and store roughly 4.3 billion tonnes of carbon dioxide equivalent each year, a figure that represents about 11 percent of all the carbon humanity released through fossil fuel burning in 2021. When grasslands remain undisturbed, they function as some of the most reliable carbon sinks the planet possesses.
But the map tells a darker story as well. Agricultural practices have fractured this hidden world at an alarming pace. Croplands contain, on average, only about half the fungal density found in natural grasslands and other intact ecosystems. Tilling, monoculture planting, and the application of certain chemicals have systematically dismantled networks that took millennia to establish. Each acre converted to industrial agriculture represents not just a loss of topsoil or a shift in what grows there—it represents the destruction of an intricate living system that regulates nutrient cycling and carbon storage across the globe.
The implications are profound. As agricultural expansion continues and farming practices remain largely unchanged, humanity is not only reducing the capacity of soils to feed plants naturally; it is also diminishing one of Earth's most powerful mechanisms for removing carbon from the atmosphere. The map makes visible what was previously only theorized: that the health of the soil beneath our feet, and the invisible life within it, may be as critical to the planet's future as the forests we can see.
Citações Notáveis
Fungi form microscopic thread-like structures that weave through soil, linking to plant roots in a partnership where fungi supply nutrients and plants provide carbon-rich sugars— Scientific researchers mapping the fungal network
A Conversa do Hearth Outra perspectiva sobre a história
When you say these fungi absorb 4.3 billion tonnes of carbon dioxide a year, how does that actually happen? Are they breathing it in?
Not quite. The fungi don't breathe carbon dioxide the way we do. They're storing carbon that plants give them—sugars made from photosynthesis. When the fungi die and decompose, or when they're undisturbed in the soil, that carbon stays locked underground instead of returning to the atmosphere.
So the fungi are essentially a storage system for carbon that would otherwise cycle back into the air.
Exactly. And the remarkable part is that this happens automatically, without human intervention. A healthy grassland just does this work continuously. But the moment you plow it up or treat it with chemicals, you break the network and release the stored carbon.
Why does agriculture destroy these networks so thoroughly? Is it just the plowing?
Plowing is part of it—it physically tears apart the fungal threads. But it's also monoculture. Fungi form partnerships with specific plants. When you plant the same crop year after year, you're eliminating the diversity of plants the fungi evolved to work with. Add in fungicides and certain fertilizers, and you've essentially poisoned the partnership.
If we know this now, can we rebuild these networks in agricultural land?
That's the question everyone is asking. Some farmers are experimenting with reduced tillage and crop rotation to let the networks recover. But rebuilding what took millennia to establish takes time—and time is what we don't have with carbon in the atmosphere rising.
So this map is really a warning, then.
It's both. It shows us what we have to lose, and it gives us proof of what we're losing. That's the first step toward changing course.