Deep beneath your feet, there is a vast, sprawling, unfathomably huge network of fungi that, when laid end to end, would extend for a mind-boggling 68 quadrillion miles.

According to a new study published in Science, researchers have created the first global map of Earth’s massive underground fungal network, a tangled web of tendrils so long that it would stretch nearly a billion times the distance from Earth to the Sun. It’s so big that comparisons like that fail to capture the sheer enormity of the fungal network underneath us.

These organisms are known as arbuscular mycorrhizal fungi and are intertwined with around 70 percent of the Earth’s plants. They attach themselves to roots and act like a complex shipping system that delivers water, nitrogen, and phosphorus to plants, and all it asks in exchange is some carbon to feed off of.

Without this tangled web, our ecosystems wouldn’t function as they do. Think of it as a planet-sized version of your body’s circulatory system.

Scientists estimate the network contains about 300 megatons of carbon, or roughly four to six times the carbon stored in all living humans combined. Every year, this vast network of fungi moves and stores carbon underground, regulating the Earth’s climate in the process.

To make a map of something so vast, so complex, researchers analyzed more than 16,000 soil samples collected from around the world and combined that data with machine learning models and robotic imaging technology that’s capable of measuring hundreds of thousands of fungal filaments. With all that combined, the research team produced the clearest picture yet of the living system that is largely invisible yet connects everything.  

Researchers found that some of the densest areas of connection are beneath grasslands, wetlands, and prairies, and, surprisingly, not in big, lush forests as one would assume. Places like the Florida Everglades are some of the world’s most vital sources of underground fungal life.

Well, the mapping of this vast network is in itself incredible; it does come with a bit of unease. Researchers found that fungal density in croplands is about half of what you would find very deep underground in wild ecosystems. Even more concerning is that grasslands, which beneath them store about 40 percent of the world’s fungal biomass, are rapidly disappearing thanks to development and ecological damage.