First Global Map Reveals Vast Underground Fungal Networks

Mapping the Hidden World Beneath Our Feet

For the first time, researchers have produced a global digital map of the vast underground networks of fungi that crisscross the planet just beneath the surface. The map reveals an astonishing 110 quadrillion kilometers of carbon-rich mycelium intertwined with plant roots, highlighting a hidden infrastructure that is vital for ecosystem health and climate regulation.

The study, led by Justin Stewart and Toby Kiers of the Society for the Protection of Underground Networks, compiled data from over 16,000 soil samples across the globe, derived from 322 previous studies. They also used robotic imaging to measure more than 300,000 fungal threads grown in the lab, enabling them to estimate total biomass and carbon storage. The results provide the most comprehensive picture yet of arbuscular mycorrhizal fungi, an ancient group that forms symbiotic relationships with about 70% of the world's plant species.

The Symbiotic Partnership

Arbuscular mycorrhizal fungi exchange nutrients and water with plants in return for carbon. This mutualism is so widespread that plants without such partnerships are considered outliers. “Some people call plants the saviours of these fungi, but these fungi are also the saviours of plants,” says Stewart. “If you’re not in symbiosis with arbuscular mycorrhizal fungi, you’re kind of the weirdo of the plant world.”

The carbon stored in these fungal networks is immense: the researchers estimate it is equivalent to about five times the mass of all living humans combined. This carbon sequestration capacity makes the fungi a critical player in mitigating climate change. “They’re very important for a lot of the different functions of our planet,” says Stewart. “For example, they pull carbon underground – that’s important for climate change.”

Global Distribution and Threats

The map reveals that around 40% of the world's arbuscular mycorrhizal fungi reside in grassland ecosystems, particularly in South Sudan, the Florida Everglades, and the Tibetan plateau. This concentration is concerning because grasslands are rapidly being converted to farmland. Croplands show significantly reduced fungal presence, likely due to intensive agricultural practices that disrupt the delicate underground networks.

The loss of these fungi could have cascading effects on plant health, soil fertility, and carbon storage. As grasslands are plowed under for agriculture, the carbon held in fungal networks is released into the atmosphere, exacerbating climate change. The researchers emphasize the need to protect these ecosystems to preserve the vital services provided by mycorrhizal fungi.

Implications for Climate and Agriculture

Understanding the scale and distribution of fungal networks opens new avenues for climate change mitigation. By preserving and restoring these networks, we could enhance natural carbon sinks. Additionally, agricultural practices that promote fungal health, such as reduced tillage and cover cropping, could improve crop yields and soil resilience.

The study also underscores the interconnectedness of life on Earth. The fungal networks act as a kind of underground circulatory system, moving nutrients and carbon across vast distances. This discovery challenges the traditional view of plants as independent organisms and highlights the importance of cooperation in nature.

As the global map becomes a tool for researchers and policymakers, it may inform conservation strategies and land-use decisions. The next step, according to the team, is to refine the map with more local data and to monitor changes over time. “We asked the question: can we map the Earth’s underground circulatory system?” says Kiers. With this groundbreaking map, they have answered with a resounding yes.

This article is based on reporting by New Scientist. Read the original article.