Mycorrhizal fungi live in symbiosis with plant roots, exchange nutrients for carbon, support agricultural production, and contribute to carbon storage in soils. Yet, we still know little about where these fungi occur, how their biodiversity is distributed, and how they respond to land use and climate change.
Stewart investigated where underground fungal diversity is highest and which factors determine these patterns. They used AI models to link nearly 3 billion DNA sequences from thousands of soil samples to satellite data. This allowed them to map fungal diversity worldwide.
Hotspots poorly protected
The models showed that most global fungal diversity hotspots are poorly protected: less than 10 percent overlap with protected nature reserves. Stewart then produced a global priority map for fungal sampling, showing that over 70 percent of ecosystems remain underexplored.
Furthermore, they demonstrate that the main drivers of differences in fungal diversity depend on the spatial scale. At the global scale, climate plays the largest role, while at smaller scales, local interactions between climate and land use determine which fungi occur around roots.
Stewart: “My research shows that underground biodiversity is a crucial but often invisible part of the health of our planet. Mycorrhizal fungi play a disproportionately large role in this, because they support ecosystems, agriculture, and carbon storage. Until now, however, useful, large-scale information about where these fungi occur and what threats they face has been lacking. Imagine a world in which we wouldn't know where the Amazon rainforest is located, or where the greatest risks to its biodiversity lie.”
Underground Atlas
Stewart makes the maps and analyses available through the Underground Atlas platform of the Society for Protection of Underground Networks (SPUN). This makes the data accessible to policymakers, land managers, and conservationists. They can use these maps to better protect threatened underground hotspots, target restoration projects in vulnerable regions, and make agriculture more sustainable.
Stewart: "In the short term, these insights can help prioritize protected areas. In the longer term, they will support international nature and climate policies that also consider the soil life."
Stewart will defend their doctoral research on February 10.