Sixty-Eight Quadrillion Miles of Hidden Network Beneath Your Feet

There’s an invisible circulatory system pumping nutrients and storing carbon all around us—and it’s almost impossibly vast. We’re talking about arbuscular mycorrhizal fungi, those threadlike filaments woven through soil worldwide in quantities so staggering they defy comprehension: sixty-eight quadrillion miles of fungal network.

A groundbreaking new study, recently covered by the New York Times and highlighted by Executive Editor Will Doig, used machine learning to map this subterranean web and measure how it varies across different ecosystems. What emerged is both humbling and urgent: the densest fungal networks are found beneath grasslands—and that matters more than you might think. These ecosystems function as some of the planet’s most important carbon sinks, quietly absorbing and storing carbon that would otherwise warm the atmosphere.

If you caught Reasons to be Cheerful’s Fungi Week coverage, this research deepens that story considerably. It’s not just about the remarkable organisms living in soil; it’s about understanding how fundamentally dependent planetary health is on these hidden filaments. The fungi transport nutrients to plants, help them grow stronger, and in turn lock away carbon. The scale is staggering. The stakes are real.

What makes this study particularly valuable is the methodology itself. Machine learning doesn’t just estimate—it maps with precision, revealing regional variations that help scientists understand where these networks thrive and where they’re vulnerable. It’s the kind of breakthrough that transforms an abstract concept (a fungal network) into measurable, actionable data.

The takeaway: the ground beneath grasslands everywhere is doing heavy ecological lifting. And the more we understand how these networks function, the better positioned we are to protect them.