Grasslands harbor the planet's densest fungal networks, not rainforests
Beneath the surface of nearly every landscape on Earth, an ancient partnership between fungi and plant roots has been quietly sustaining life for over 400 million years — and now, for the first time, scientists have mapped it. The resulting picture challenges long-held assumptions, revealing that wild grasslands, not tropical rainforests, harbor the densest mycorrhizal networks on the planet. This discovery invites us to reconsider not only where biological complexity hides, but which ecosystems we have been too quick to overlook in our efforts to protect the living world.
- A global synthesis of thousands of soil studies has produced the first-ever map of mycorrhizal fungal networks, making visible a biological system that connects roughly 70 percent of Earth's plant life.
- The finding directly contradicts decades of scientific assumption — rainforests, long treated as the crown jewels of underground biodiversity, have been quietly outpaced by wild grasslands.
- These fungal networks are not incidental; they are the mechanism by which plants access soil nutrients, and their health is tightly bound to the planet's capacity to store carbon and resist climate disruption.
- Grasslands worldwide have been steadily lost to agriculture and development, and this map now reframes that loss as a threat not just to surface ecosystems but to the hidden architecture sustaining them.
- Researchers are pressing forward with urgent questions about how these networks respond to disturbance, climate shift, and whether they can be deliberately cultivated to restore degraded soils.
Beneath the grass at your feet lies a network so vast it could, unspooled, reach the sun. Scientists have completed the first global map of mycorrhizal fungi — the threadlike organisms that wrap around the roots of roughly 70 percent of Earth's plants — and the discovery upends what we thought we knew about where these networks thrive.
For decades, researchers assumed rainforests would harbor the planet's most intricate underground ecosystems. More plants above ground, the logic went, meant more fungal partners below. The new map tells a different story: the fungal networks are thickest not in tropical forests but in wild grasslands scattered across the globe, forcing a recalibration of how we understand the hidden architecture of life on land.
Mycorrhizal fungi operate through an ancient bargain. In exchange for sugars a plant produces through photosynthesis, fungi unlock nutrients — phosphorus, nitrogen, minerals — that the plant cannot access alone. This partnership evolved more than 400 million years ago, and without it, most terrestrial plants would struggle to survive. Mapping something so vast yet invisible required synthesizing data from thousands of studies and soil samples across every continent, revealing that these networks follow patterns tied to climate, soil type, and plant community.
The implications extend well beyond biology. Soil health, carbon sequestration, and ecosystem resilience are all intimately tied to fungal activity. Grasslands — now mapped as the densest repositories of this fungal life — may play a far larger role in planetary carbon cycling than anyone previously recognized. And if conservation funding has long flowed toward rainforests partly on the assumption that they contained the most complex underground life, this map suggests grasslands deserve comparable protection. Many have already been lost to agriculture and development; preserving what remains now carries an additional and urgent weight.
The map is not an endpoint. It is an invitation to ask how these networks respond to disturbance, how they might adapt as climate zones shift, and whether we can harness them to restore degraded land. For the first time, we can see the shape of something that has always been there — working in the dark, connecting nearly everything that grows.
Beneath the grass at your feet lies a network so vast that if you could stretch it out in a single line, it would reach the sun. Scientists have just completed the first global map of mycorrhizal fungi—the threadlike organisms that wrap around the roots of roughly 70 percent of Earth's plants—and the discovery upends what we thought we knew about where these networks thrive most densely.
For decades, researchers assumed that rainforests, with their explosive biodiversity and tangled canopy, would harbor the planet's most intricate underground ecosystems. The logic seemed sound: more plants above ground meant more fungal partners below. But the new map tells a different story. The fungal networks are thickest not in tropical forests but in wild grasslands scattered across the globe. It's a finding that forces a recalibration of how we understand the hidden architecture of life on land.
Mycorrhizal fungi operate through a bargain struck between two organisms. The fungi extend their filaments into plant roots, and in exchange for sugars that the plant manufactures through photosynthesis, the fungi unlock nutrients locked in the soil—phosphorus, nitrogen, and other minerals that the plant cannot access on its own. It is one of nature's oldest and most successful partnerships, having evolved more than 400 million years ago. Without these fungi, most terrestrial plants would struggle to survive.
What makes the new map significant is not just that it exists—it is that it exists at all. Mapping something invisible, something that lives in darkness and operates at scales both vast and microscopic, required researchers to synthesize data from thousands of studies, field observations, and soil samples collected across every continent. The resulting picture reveals that these fungal networks are not scattered randomly but follow patterns tied to climate, soil type, and plant community composition. Grasslands, it turns out, create conditions where these fungi flourish in exceptional abundance.
The implications ripple outward in multiple directions. Soil health depends on these networks. Carbon sequestration—the process by which carbon dioxide is pulled from the atmosphere and stored in soil—is intimately tied to fungal activity. As the climate warms and ecosystems face mounting stress, understanding where and how these networks function becomes not merely academic but urgent. Grasslands, now mapped as the densest repositories of fungal diversity, may play a larger role in planetary carbon cycling than previously recognized.
The map also challenges conservation priorities. If rainforests have long dominated funding and attention partly because they were assumed to contain the most complex underground life, this new understanding suggests that grasslands deserve comparable investment and protection. Many grasslands worldwide have been converted to agriculture or urban development. Restoring them, or protecting what remains, now carries an additional weight: preserving the fungal networks that sustain them and, by extension, the broader health of terrestrial ecosystems.
Scientists are already asking what comes next. How do these networks respond to disturbance? How might they adapt—or fail to adapt—as climate zones shift? Can we harness knowledge of fungal networks to improve agricultural soil health or accelerate ecosystem restoration? The map is not an endpoint but an invitation. For the first time, we can see the shape of something that has always been there, working in the dark, connecting nearly everything that grows.
The Hearth Conversation Another angle on the story
So these fungi are everywhere—70 percent of plants. Why didn't we know this before?
We knew fungi existed and that they partnered with plants. What we didn't have was a global picture of where they were densest and how they were distributed. It's the difference between knowing your neighbor exists and actually seeing their house on a map.
And the surprise is that grasslands have more of them than rainforests?
Yes. Rainforests are incredibly biodiverse above ground, so the assumption was that underground would follow the same pattern. But grasslands create different conditions—different soil chemistry, different plant communities—that apparently favor these fungal networks in ways we didn't anticipate.
What does this change about how we should treat grasslands?
It means grasslands aren't just pretty or good for grazing. They're repositories of one of Earth's most important biological networks. If we destroy them, we're not just losing grass—we're dismantling infrastructure that holds soil together and cycles carbon.
Can we use this map to fix damaged soil?
That's the hope. If we understand where and why these networks thrive, we might be able to restore them in degraded areas or protect them where they still exist. It's early, but the map gives us a foundation to work from.
Does this change anything about climate change?
Potentially, yes. If grasslands are major players in fungal networks, and fungal networks are major players in carbon storage, then grassland conservation becomes a climate strategy, not just an environmental one.