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The Underground Atlas by SPUN reveals that over 90 per cent of mycorrhizal fungi hotspots are outside protected areas
This highlights the need for their inclusion in climate and conservation agendas
These fungi, crucial for nutrient cycling and carbon sequestration, have been largely overlooked despite their vital role in sustaining ecosystems and supporting plant health
The best soils in the world are the ones that are alive with beneficial organisms. These include large organisms such as earthworms and nematodes, and microorganisms such as bacteria and fungi.
However, very little is known about the fungal component of the soil. Mycorrhizal fungi live symbiotically with more than 80 per cent of plant species on earth and make as much as 30 per cent of living microbial biomass in the soil.
This group of fungi helps the plant soak in nutrients such as phosphorus from the soil. They also play an important role in carbon sequestration as they use the carbon dioxide (CO2) released by the plant roots. This is as much as 13 billion tonnes of CO2 per year, which is equivalent to around a third of global emissions from fossil fuels.
Mycorrhizal fungi have been overlooked in climate change strategies, conservation agendas and restoration efforts. The lack of information about their distribution around the world makes it difficult to develop ways to protect them. The Underground Atlas prepared by the Society for the Protection of Underground Networks (SPUN) could help fill this gap in knowledge.
"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," said Toby Kiers, executive director, SPUN. "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,” he added.
This digital atlas provides information about global distribution of two of the three types of mycorrhizal fungi: ectomycorrhizal (EcM) fungi; arbuscular mycorrhizal (AM) fungi. The third, ericoid mycorrhizal (ErM) fungi is rare and not many samples were available.
The researchers used 25,000 geolocated soil samples comprising more than 2.8 billion fungal DNA sequences from 130 countries to train machine-learning algorithms that can predict mycorrhiza richness and rarity across terrestrial ecosystems. On the basis of these predictions, they generated high-resolution, global-scale maps to identify key reservoirs of highly diverse and endemic mycorrhizal communities.
Using these, the researchers predicted major hotspots of AM fungal richness and endemicity across savannas of the Brazilian Cerrado, tropical forests across Southeast Asia and Guinean forests in West Africa. EcM fungal richness hotspots were predicted throughout northern forest ecosystems and included much of the Siberian and Canadian boreal forest regions, temperate coniferous forests across Western United States and Canadian mountain ranges, and temperate broadleaf and mixed forests in Central Europe and the North American Great Lakes region.
The researchers also found that over 90 per cent of mycorrhizal biodiversity hotspots lay outside protected areas. They said that there is an urgent need to include mycorrhizal fungi in the climate and conservation agendas.
Lack of knowledge about soil biodiversity also prompted the Food and Agriculture Organization of the United Nations (FAO) to take steps to measure, monitor and protect soil biodiversity. The global body launched the Global Soil Biodiversity Observatory (GLOBSOB) at COP15 of the Convention on Biological Diversity to provide a global reference for scientific collaboration and policy design.
“While various knowledge-sharing platforms and initiatives have been launched, there is currently a lack of standardised monitoring protocols and actionable strategies for integrating soil biodiversity into policy and national monitoring frameworks,” said Jacob Parnell in the journal Nature Ecology and Evolution. He and his team wrote a commentary on the GLOBSOB on July 14.
The observatory is a tiered system. It allows for steady expansion of measurement capacities to extend from soil chemical properties, enzymatic activities and to tracking decomposition patterns using leaf litter bags. It can steadily increase to more complex nutrient cycling components and on to intraspecific microbial genetic diversity through shotgun metagenomic sequencing.
FAO already leads the Global Soil Partnership, which held its 13th Plenary Assembly last June. It serves as a hub for other initiatives and has catalysed successful conservation projects, such as the Soil Doctors and Recarbonization of Global Agricultural Soils.
“From the early days of global soil mapping in the 1960s, to combating desertification across the Sahel, Latin America and Asia, and more recently, pioneering soil mapping with cutting-edge technology, FAO has consistently been a champion of soil health as a foundation of global food security,” said FAO Director-General QU Dongyu.
Final summary: Mycorrhizal fungi, vital for plant health and carbon storage, have been largely ignored in conservation efforts. The Society for the Protection of Underground Networks has created a digital atlas to map their global distribution, revealing that most hotspots are unprotected. This underscores the need for integrating soil biodiversity into environmental policies, as emphasised by the FAO's recent initiatives.
