Earth's underground fungal network is so vast that, if it were in outer space, it would span roughly 10% of the Milky Way if placed in a straight line, a new study finds.

These subterranean structures, called arbuscular mycorrhizal fungal networks, work in partnership with most of the world's land plants, feeding plants nitrogen and phosphorus in return for their carbon. Now, the first global map of this fungal network has revealed where their intricate branching structures are most densely packed.

In grasslands that are high-altitude or flooded grasslands, such as the Everglades in Florida, the top 6 inches (15 centimeters) of soil are especially dense, containing around 40% of the global fungal biomass. This highlights that undisturbed grasslands are an essential, reliable carbon sink, according to the research, which was published Thursday (June 11) in the journal Science.