One billion times the distance from the Earth to the sun: First global map of mycorrhizal fungi reveals true scale of underground networks across the planet
Society for the Protection of Underground Networks
image:
Global map of hyphal density of AM fungi.
view moreCredit: Truth & Beauty / Moritz Stefaner Justin Stewart - SPUN
Mycorrhizal fungi form underground networks that sustain plant life and help regulate Earth’s climate by drawing carbon into soils. In a study published today in Science, an international team of researchers produced the first global maps estimating the distribution and mass of the Earth’s arbuscular mycorrhizal fungal networks. Published alongside an interactive visualization that helps reveal the scale of this underground fungal infrastructure, the research will help scientists and decision makers understand where these vital fungal systems are thriving and where they are threatened.
Researchers found:
Global topsoils contain ~110 quadrillion kilometers of arbuscular mycorrhizal fungal network – made up of tubular cells known as hyphae. This distance is almost a billion times the distance from the Earth to the sun.
Grassland ecosystems are home to an estimated ~40% of Earth’s arbuscular mycorrhizal fungal infrastructure. The flooded grasslands of South Sudan, the Everglades in Florida, and the Tibetan plateau have exceptionally high predicted network density.
AM fungal networks transport an estimated ~4 billion tons of CO2e into soils each year (equivalent to 11% of all human-related carbon-dioxide emissions).
On average, large-scale agricultural crop lands are predicted to be associated with ~50% lower network densities. While more work is needed to link specific farming practices to mycorrhizal health, scientists worry that less dense networks diminish a soils’ ability to store carbon, cycle nutrients, and resist stress.
Arbuscular mycorrhizal fungi (known as AM fungi) form symbiotic trade relationships with ~70% of plant species on Earth. The fungi provide nutrients and water in exchange for carbon produced by plants. As ecosystem engineers, these networks form a critical living infrastructure that draws carbon into soils and supports much of life on Earth. Last year, in Nature, researchers published global analyses of the diversity patterns of underground mycorrhizal fungal communities accompanied by a digital tool, the Underground Atlas, to help decision-makers locate predicted underground biodiversity hotspots. But until now, no-one has attempted to predict and visualize the physical density and global distribution of AM fungal networks.
The researchers assembled data on the density of AM networks from over 16,000 soil-cores collected across Earth. They developed machine-learning models that incorporated data layers from deserts and tundra to forests to predict network density in unsampled ecosystems. In collaboration with the Physics of Behavior group at research institute AMOLF, the team calibrated their model with robotic imaging of over 300,000 living AM fungal hyphae grown in the lab. Using these datasets, they estimate that AM fungal networks have a total length of ~110 quadrillion kilometers and a mass of ~300 megatons of carbon (4-6x the mass of all living humans).
“It is hard to overstate the importance and enormity of these fungi” said lead author Dr. Justin Stewart, with the Society for the Protection of Underground Networks (SPUN). “There could be up to 10 meters (32 feet) of mycorrhizal network in just a teaspoon of soil.”
Often called one of the Earth’s circulatory systems, mycorrhizal networks move carbon, water, and nutrients across underground ecosystems. In healthy soils, mycorrhizal networks can increase the foraging area of plant roots by up to 100 times, while providing > 80 percent of a plant’s phosphorous.
“With the emergence of new technologies in high-resolution imaging, machine-learning and robotics, we are starting to reveal what has long been hidden under our feet” said co-lead author, Dr. Corentin Bisot, an AMOLF biophysicist. “We are learning how the complex bodies of network-forming fungi transport nutrients and help regulate the climate.”
The team worked with award-winning data visualization designer Moritz Stefaner to build the Mycorrhizal Infrastructure Map. It is the first time the Earth’s fungal infrastructure has been seen at this scale and resolution (estimates are calculated for every 1km2 of terrestrial land, excluding ice caps and areas lacking enough data to predict). The underlying data are available to download for governments and decision-makers to begin monitoring the health of critical underground fungal communities.
Last year, several of the same authors published a cover story in Nature in which they described how mycorrhizal fungal networks and their plant partners build hyper-efficient supply chains to trade carbon and nutrients, measuring carbon flows inside these living transport systems that can reach speeds of up to 120 um/sec (if one was inside the network, these speeds would feel like ~400km/hr). The current study is a critical step towards understanding how carbon and nutrient flows unfold on a global scale.
The study also documented potential threats. Mycorrhizal densities across croplands are predicted to be roughly half those in wild ecosystems. Wild grassland ecosystems were found to contain ~40% of the world’s arbuscular mycorrhizal biomass. Yet grasslands are among Earth’s least protected ecosystems and are being transformed into farmlands four times faster than forests. This reinforces a finding published by SPUN researchers last year showing that 95% of the biodiversity hotspots for arbuscular mycorrhizal fungi are located outside protected areas.
For evolutionary biologist Dr. Toby Kiers, Executive Director of SPUN, this growing body of research is critical in developing more precise climate policies. “Fungi have been ignored in climate and conservation for too long. Now is the time to change that trajectory.” Kiers was recently named a prestigious MacArthur Fellow and winner of the Tyler Prize, known as the “Nobel Prize for the Environment,” for her work on plant-fungal systems.
“Mycorrhizal fungi have shaped life on earth for hundreds of millions of years, but we still understand too little about how the infrastructure of these living transport systems is distributed across the planet,” added co-author and biologist Dr. Merlin Sheldrake. “This study is an exciting step towards understanding how this planetary circulatory system operates and suggests 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.”
This study helps quantify the extraordinary extent of AM fungal networks, but it also reveals how much remains unknown by pinpointing many regions of the planet which remain unsampled.
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Society for the Protection of Underground Networks (SPUN):
SPUN was founded in 2021 as a non-profit scientific research organization with a mission to map and protect Earth’s mycorrhizal networks. In collaboration with researchers and local communities, SPUN is accelerating efforts to protect the underground ecosystems largely absent from conservation and climate agendas. To learn more about SPUN, visit: https://spun.earth/.
Media contact:
Magda Czyz
magda@spun.earth
Society for the Protection of Underground Networks (SPUN)
Link to press kit:
Photos and more information
All Authors:
Justin D. Stewart, Corentin Bisot, Rachael I.M. Cargill, Michael E. Van Nuland, Heidi Jayne Hawkins, Loreto Oyarte Galvez, Malin Klein, Marije van Son, Victoria Terry, Louis Paré, Claudia Banchini, Franck Stefani, Felix Kahane, Kai-Kai Lin, Renato K. Braghiere, Katie J. Field, Nadejda A. Soudzilovskaia, Jinsu Elhance, Vasilis Kokkoris, Merlin Sheldrake, James T. Weedon, Thomas S. Shimizu, Stuart West, E. Toby Kiers
Network architecture of fungal mycelium. Mycelial architecture varies across strains and species. Networks imaged at the AMOLF biophysics institute in Amsterdam.
Credit
Corentin Bisot - VU Amsterdam, AMOLF Justin Stewart - SPUN
Mycorrizhal fungi under the microscope at AMOLF biophysics institute in Amsterdam. The circular structures are spores. Color is altered for legibility.
Credit
Tomás Munita
Close up of soil core extraction.
Credit
Tomás Munita
Fungal networks imaged using a microscope at AMOLF biophysics institute in Amsterdam. Threads are arbuscular mycorrhizal hyphae.
Credit
Loreto Oyarte Gálvez - VU Amsterdam, AMOLF
Journal
Science
Method of Research
Data/statistical analysis
Subject of Research
Not applicable
Article Title
Global density and biomass of arbuscular mycorrhizal fungal networks
Article Publication Date
11-Jun-2026
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- One billion times the distance from the Earth to the sun: First global map of mycorrhizal fungi reveals true scale of underground networks across the planet
(Society for the Protection of Underground Networks)
Capacity of certain unicellular organisms to stick together may be key to animal evolution
Indiana University
A recent study by Ruibao Li and Jennah Dharamshi published in Nature may help us understand the beginnings of animal evolution billions of years ago. These findings are the result of a collaboration between researchers at Indiana University Bloomington, the Institute of Evolutionary Biology in Spain and Uppsala University in Sweden, and was led by J. P. Gerdt and Iñaki Ruiz-Trillo.
These researchers found that after feeding a specific bacteria to a certain unicellular relative of animals, the single cells began to stick to one another, revealing a possible mode by which our ancestors began to evolve into animals billions of years ago.
Animal bodies are made up of trillions of cells that stick together and cooperate. Billions of years ago — before animals evolved — every living thing on earth was a single-celled organism. Eventually some of these cells began sticking together, working together and then reproducing as multicellular organisms. Some of these early multicellular organisms evolved into present-day plants or fungi, while others evolved into animals.
How the cells began to stick together and why they did so has long been a mystery to scientists. To get to the bottom of this enigma, Li and his colleagues studied Ministeria vibrans, a unicellular organism that shares ancient ancestors with present-day animals.
M. vibrans survives by eating bacteria. Li rigorously tested different bacterial foods until he found one that encouraged single M. vibrans cells to stick together and become multicellular. The bacteria got trapped between the aggregating cells, meaning that it was more efficient for M. vibrans to collect food by sticking together rather than remaining as single-celled organisms. Further, by sticking together, the cells might be able to protect their food from other organisms.
Sticking together also provides opportunities for cells to exchange genes via mating, which may produce new genetic combinations that enable adaptation to new environments.
Li and Dharamshi observed that when M. vibrans evolved from unicellular to multicellular, it produced the same proteins that many animal cells use to stick together. The multicellular form of M. vibrans also produced many proteins that animal cells use to communicate and coordinate behavior. The team concluded that the unicellular organisms that evolved into animals also likely used these proteins to form multicellular bodies and cooperate.
Li and his colleagues are excited to uncover further insights from the aggregation behavior of M. vibrans. Because the organism is much simpler than humans, it is easier to study, meaning it could even help reveal overlooked genes involved in certain developmental processes or diseases.
However, “What this organism is most powered to answer is what the unicellular ancestor of animals was like,” said J. P. Gerdt, associate professor of chemistry at Indiana University Bloomington. “It’s one of the best systems we have to go back a billion years to see what our ancestors were like at that stage.”
Journal
Nature
Method of Research
Observational study
Subject of Research
Cells
Article Title
A unicellular relative links aggregative multicellularity to animal origins
