110-quadrillion-kilometer fungal network moves CO₂ equal to about 11% of annual human emissions into soil each year

From a walk through a neighborhood park to a hike through a national forest to a child jumping in his backyard puddle, one of Earth's greatest engineering feats is at work in each of these everyday moments. It’s not steel beams, fiber optic cables, or Wi-Fi. But it works silently, connecting plants, recycling nutrients, and helping regulate the planet's climate.

According to a landmark 2026 study published in the journal Science by an international research team led by first author Justin Stewart of Vrije Universiteit Amsterdam, alongside the Society for the Protection of Underground Networks (SPUN) and contributors from the University of Sheffield, have found that the Earth's soils contain 110 quadrillion kilometers of tiny fungal threads. This staggering biological infrastructure is equivalent to approximately 1 billion times the distance from the Earth to the Sun.

These underground networks transport plant-derived organic carbon, produced when plants convert atmospheric carbon dioxide into sugars through photosynthesis, into soils. Scientists often express the scale of this transfer as carbon dioxide equivalents (CO₂e), allowing it to be compared with human emissions. They are perhaps one of the most underutilized allies in the fight against climate change. We have charted continents and oceans and even far galaxies, as National Geographic observed; but below our feet lies an extensive living framework which has long been less visible.


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These are not mushrooms that sprang up with the rain. They are microscopic organisms referred to as arbuscular mycorrhizal (AM) fungi with thread-like strands called hyphae extending through soil. Partnering with nearly 70 percent of all plant species, they deliver phosphorus, nitrogen, water, and other nutrients directly to plant roots. In exchange, plants feed them carbon, which is produced as a by-product of photosynthesis, a trade that has been going on for hundreds of millions of years

According to the Science study titled “Global density and biomass of arbuscular mycorrhizal fungal networks,” the research team compiled data from 322 previous studies, using more than 16,000 soil samples, along with machine-learning models and robotic high-resolution imaging of more than 300,000 fungal hyphae to create the first estimate of the global distribution of these fungal networks and their density. It is like a blueprint for one of Earth's secret life support systems.

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In the discussions surrounding climate, solar farms, electric cars, or carbon capture technology are likely to come up. They don't talk a lot about fungi. Perhaps they should. A ground-breaking 2023 research paper published in Current Biology estimated that all mycorrhizal fungi collectively receive 13.12 billion tonnes of CO₂ equivalent from plants each year, amounting to roughly 36% of global annual fossil fuel emissions.

Out of that total, AM fungi alone receive and transfer the equivalent of about 4 billion tonnes of CO₂ worth of plant-derived carbon into soils annually, roughly 11% of yearly human-caused global emissions. While the comparison is expressed in CO₂ equivalents for climate accounting, the material actually moving through the fungal networks is organic carbon supplied by plants. This is nothing like hiding carbon in futuristic, underground vaults, as Ars Technica noted. It's something that nature has done for a long time, possibly before the term ‘net zero' even gained popularity in the scientific lexicon. Sometimes it's right under our noses, and we just don't realize it.

America's soil has a story to tell

The results are of special importance for the United States. Fungal networks contribute to soil fertility, crop productivity, drought resistance and biodiversity all across the globe, including Iowa's farmlands, vineyards in California and the forests of the Appalachian region. Yet the study found that arbuscular mycorrhizal fungal networks are, on average, about 50% percent less dense in croplands than in nearby wild ecosystems. Researchers attribute much of this decline to intensive agricultural practices such as tilling, which physically disrupts fungal threads, as well as overfertilization, which further breaks these underground partnerships.

It looks like a good deal of irony. As these underground networks shrink, soils become less efficient at storing carbon and cycling nutrients. The importance of soil fungi is not something that is just environmental; it is now a challenge to protect soil fungi. It is becoming increasingly significant in the field of agriculture, economy, and food security.

Mapping what we couldn't see

Up until recently, research into fungal associations was conducted primarily through isolated field studies. It was difficult to map their connection around the world. This is where the SPUN research comes in. The maps show areas of exceptional fungal density, and show large areas where soils have not been sampled, providing clues on how to conserve, restore and develop climate policy.

The Guardian says the maps might be of use to governments in recognising underground ecosystems as a natural resource to be protected, like wetlands or old-growth forests. While it's outside the public eye, Smithsonian Magazine also reported that the fungi aid up to 90% of plant species, and yet are rarely talked about.

Why these underground networks deserve visibility

Nowadays, in modern society, people often tend to glorify what is easily captured on camera. The fungi, in contrast, work from the shadows, unobtrusive and unheralded, quietly performing their ecological chores.

Perhaps that's changing. In this new fungal atlas, we are reminded that the most influential workers in nature are often the least noticed. Healthy ecosystems depend not only on the charismatic animals and big trees, but also on the billions of relationships beneath each footfall. Next, when you are on a hiking trail, or in your own backyard, think: “I'm not standing on dirt.” You're perhaps above one of the oldest and most sophisticated living networks on Earth, networks that have been holding ecosystems together long before the construction of roads, laying cables, or the online world.