- Scientists made the first detailed global maps of mycorrhizal fungal networks by analyzing DNA from 25,000 soil samples worldwide, showing where these fungi that partner with most plants are most diverse.
- Less than 10% of the areas with the highest fungal diversity are currently protected, leaving important underground ecosystems at risk from farming and development.
- Major hotspots include Ethiopia’s Simien Mountain foothills, Brazil’s Cerrado savanna, West African rainforests and Tasmania’s forests, with different types of fungi thriving in tropical versus temperate regions.
- A new Underground Atlas tool allows users to explore fungal diversity patterns anywhere on Earth, revealing biodiversity hotspots that traditional conservation approaches have overlooked.
With nearly every step, we move above a vast underground network of fungal filaments, an ancient communication system that predates human civilization by hundreds of millions of years. Now, scientists have created the first comprehensive maps of these hidden networks.
These maps, published in a new study in Nature, represent a four-year effort by the Society for the Protection of Underground Networks (SPUN) to understand where mycorrhizal fungi are most diverse across the globe.
The findings reveal that less than 10% of mycorrhizal fungi biodiversity hotspots fall within existing protected areas, leaving vast underground ecosystems vulnerable to destruction from agriculture and development.
“For centuries, we’ve mapped mountains, forests, and oceans. But these fungi have remained in the dark, despite the extraordinary ways they sustain life on land,” Toby Kiers, SPUN’s executive director and co-author of the paper, said in a statement. “They cycle nutrients, store carbon, support plant health, and make soil. When we disrupt these critical ecosystem engineers, forest regeneration slows, crops fail, and biodiversity aboveground begins to unravel.”
Mycorrhizal fungi form symbiotic partnerships with more than 80% of plant species, creating extensive underground networks that transport nutrients and water. These fungal webs can make up to a third of the living mass in the soil, forming what scientists describe as the “wood wide web,” allowing plants to share resources and communicate environmental threats across entire ecosystems.
Plants transfer an estimated 13 billion metric tons of carbon dioxide to these underground fungi annually, roughly equivalent to one-third of global fossil fuel emissions. Much of this carbon becomes locked in soil, making fungal networks critical for climate stability.
SPUN’s new Underground Atlas tool allows users to explore fungal diversity patterns anywhere on Earth at a resolution of 1 kilometer (0.6 miles), revealing biodiversity hotspots that traditional conservation approaches have overlooked.
To produce these new biodiversity maps, researchers used machine-learning algorithms trained on more than 2.8 billion fungal DNA sequences from nearly 25,000 soil samples across 130 countries.
Major hotspots include Ethiopia’s Simien Mountain foothills and Brazil’s Cerrado savanna, where scientists estimate there are more than 45 arbuscular mycorrhizal species per 100 square meters (about four per 100 square feet). The planet’s rarest mycorrhizal species are concentrated in West African rainforests and Tasmania’s temperate forests.
“These maps are more than scientific tools — they can help guide the future of conservation,” Michael Van Nuland, the study’s lead author and SPUN’s lead data scientist, said in a statement. “Food security, water cycles, and climate resilience all depend on safeguarding these underground ecosystems.”
The research identified two main types of mycorrhizal fungi with distinct global patterns. Arbuscular mycorrhizal fungi showed the highest diversity near the equator, following biodiversity gradients observed in plants and animals. Ectomycorrhizal fungi displayed the opposite pattern, with greatest richness in northern latitudes and southern regions of South America and Australia.
Most protected area designations focus on aboveground biodiversity, ignoring the underground networks that sustain ecosystems.
“Restoration practices have been dangerously incomplete because the focus has historically been on life aboveground,” said Alex Wegmann, a lead scientist for The Nature Conservancy and member of the SPUN Mapping Consortium, which is listed as a co-author of the study. “These high-resolution maps provide quantitative targets for restoration managers to establish what diverse mycorrhizal communities could and should look like.”
Approximately 75% of all land carbon is stored in the soil. Photo by Liz Kimbrough.
The study revealed regional differences in protection levels. Protected mycorrhizal hotspots in Asia have the lowest protection rates globally, with only 2.2% of arbuscular mycorrhizal richness hotspots and 11.3% of ectomycorrhizal richness hotspots currently protected. Europe showed the highest protection rates for arbuscular mycorrhizal hotspots at 19.6%.
Climate change also threatens fungal biodiversity hot spots. For example, Ghana’s coastline harbors exceptional fungal diversity, but coastal erosion at roughly 2 m (6 ft) per year threatens to eliminate these communities within decades. Similar threats face fungal hotspots worldwide as human activities accelerate.
“Mycorrhizal fungi need to be recognized as a priority in the ‘library of solutions’ to some of the world’s greatest challenges — biodiversity decline, climate change, and declining food productivity,” said Rebecca Shaw, chief scientist at WWF, who wasn’t involved in the study. “They deliver powerful ecosystem services whose benefits flow directly to people.”
SPUN says it is expanding its global sampling network and developing tools for policymakers and land managers. The Underground Atlas represents the beginning of efforts to make Earth’s hidden fungal diversity visible to decision-makers.
“For too long, we’ve overlooked mycorrhizal fungi,” said Merlin Sheldrake, study co-author and director of impact at SPUN. “These maps help alleviate our fungus blindness and can assist us as we rise to the urgent challenges of our times.”
Banner image : The mycorrhizal mushroom Cortinarius albomagellanicus emerges from a hyper-diverse but hidden underground fungal community in Tierra de Fuego, Chile. Image courtesy of Mateo Barrenengoa.
Liz Kimbrough is a senior staff writer for Mongabay and holds a Ph.D. in Ecology and Evolutionary Biology from Tulane University, in New Orleans, Louisiana where she studied the microbiomes of trees. View more of her reporting<here.
Microbes play leading role in soil carbon capture, study shows
Citation:
Van Nuland, M. E., Averill, C., Stewart, J. D., Prylutskyi, O., Corrales, A., van Galen, L. G., … van den Hoogen, J. (2025). Global hotspots of mycorrhizal fungal richness are poorly protected. Nature, 1-9. doi:10.1038/s41586-025-09277-4
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