Mapping the hidden fungal infrastructure
A groundbreaking study published in Science has produced the first global map of arbuscular mycorrhizal fungi, revealing networks of tubular cells called hyphae that stretch a total length of 110 quadrillion kilometres. This distance is nearly 750 million times the gap between Earth and the sun. The research, led by Dr Justin Stewart and conducted by the Society for the Protection of Underground Networks (Spun), used machine-learning models fed with data from over 16,000 soil cores collected worldwide.
These fungi form symbiotic partnerships with more than 70% of plants, exchanging nutrients and water for carbon produced by the plants. The networks have been developing for about 475 million years and play a critical role in regulating the climate by drawing carbon into soils. Despite their importance, their distribution and density across natural ecosystems have remained poorly understood until now.
How it works
Arbuscular mycorrhizal fungi consist of hyphae—microscopic tubular structures that weave through soil. Dr Stewart noted that a single teaspoon of soil can contain up to 10 metres (32 feet) of these fungal networks. The fungi provide plants with essential nutrients and water, while plants supply the fungi with carbon. This mutualistic relationship also helps store carbon underground, mitigating climate change.
The Spun team, established in 2021 by a global network of scientists, aimed to fill knowledge gaps about these underground systems. By analyzing soil cores from diverse ecosystems, they created a map that shows where fungal networks are thriving and where they are threatened.
Threats to fungal networks
The study documents significant threats to this life-giving infrastructure. On average, network densities in cropland are 47.3% lower than in wild ecosystems. Dr Stewart explained that large-scale agricultural practices harm fungal networks, particularly tilling, which rips up the soil. Fertilisers and fungicides can also disrupt the symbiosis between plants and fungi.
The consequences of losing fungal networks could be severe. Lower-density networks reduce the soil’s ability to store carbon and distribute nutrients. They also protect waterways from nitrogen, phosphorus, and other chemicals. Dr Toby Kiers, an author of the study, warned: “If they disappear, there’s going to be a lot more chemicals going into waterways.”
Why this matters
The research highlights the critical role of fungi in sustaining life on Earth. Grasslands, including the Everglades in Florida, the Sudd flooded grasslands of South Sudan, and prairie and steppe ecosystems, were found to have exceptionally high hyphal density. However, these regions are often poorly protected and increasingly degraded.
The study also reflects the potential for collaboration between farmers and fungi. Dr Stewart noted that current crop yields are artificially boosted by heavy fertiliser use. If farmers protect and support soil fungi, plants could obtain more nutrients naturally, reducing fertiliser needs, while fungi would help transfer more carbon deep into the soil, improving carbon storage.
What researchers say next
The Spun team plans to present their data to governments at the upcoming desertification Cop in Mongolia in August. Dr Kiers said: “Ultimately, the aim of the research is to help scientists and decision-makers understand where fungal systems are thriving and where they are threatened.”
Biologist and co-author Dr Merlin Sheldrake added that the study helps find “ways that we can better work with fungi to help address many of the unfolding challenges of our times, from food security to climate change.” The dataset provides benchmarks for what a healthy microbial community can look like, supporting efforts to restore underground fungal communities alongside above-ground ecosystems.
Report based on information from The Guardian.
