The study only covers living arbuscular mycorrhizal fungal networks, Stewart said, and doesn’t include dead fungal networks, which also help to store carbon and add to the total biomass and influence of the networks on ecosystems. Research into dead fungal networks is still being explored.

The study also found where these networks are most threatened. Fungal network densities across croplands are about half of what they are in wild ecosystems. Meanwhile, wild grassland ecosystems hold about 40 percent of the world’s arbuscular mycorrhizal biomass. Yet those grasslands are among Earth’s least protected ecosystems, and they are converted into farmland at four times the rate of forests, posing a potential threat to these networks and the benefits they bring to plant life and carbon storage.

Previous research from SPUN has found 90 percent of fungal communities across the globe are unprotected, and many ecosystems, like the deserts of the American Southwest, are understudied.

What exactly is driving mycorrhizal fungi losses, and the consequences of that decline, need to be explored next, the researchers said, which is why the SPUN team will be at this year’s United Nations Climate Change Conference—COP31—to present to policymakers about the importance of the networks and the role they could play in protecting ecosystems and sequestering carbon.

Understanding mycorrhizal fungi more deeply at the ground level is key, said Corentin Bisot, an AMOLF biophysicist and co-author of the study.

“We’re still far from completely understanding how, if you have a grassland next door, and you want to [increase] microbes and fungi there,” Bisot said. “We don’t have the toolbox for you to do it.”

This study, Stewart said, is just the first map. And like the first maps the Spaniards drew of California—which presented the state as an island, he said, there will be new discoveries about the density of fungi networks around the globe to grow the public’s understanding of them.

This article originally appeared on Inside Climate News, a nonprofit, non-partisan news organization that covers climate, energy, and the environment. Sign up for their newsletter here.