They support much of life on Earth, and just might hold a major key to carbon balance. We all know about magic mushrooms, nutritious mushrooms, and may have even heard about the ecosystem-healing potential of mushrooms. Now the Society for the Protection of Underground Networks (SPUN), which maps underground fungal networks, will lead the first global exploration of these fungal networks. SPUN says that the trillions of kilometres of underground networks play a critical role below the surface, moving nutrients across ecosystems.
Fungal networks are also one of the biggest untapped levers in climate science. Billions of tons of carbon dioxide (CO2) flow annually from plants into fungal networks. This carbon flow helps make soils the second largest global carbon sink, after oceans.
Globally, approximately 75% of terrestrial carbon is in the soil. This is three times more than the amount stored in living plants and animals. Fungal networks make up to 50% of the living biomass of soils.
High-resolution mycelium network | Image: ©Victor Caldas
Previous estimates had suggested five billion tons of carbon dioxide flow into fungal networks each year, equal to more than half of all energy-related CO2 emissions in 2021. Scientists are now revising this estimate, which could be three times that amount (approximately 17 billion tons), when all fungal networks are considered. High latitude below-ground ecosystems hold 13 times more carbon than rainforests.
Habitat loss, driven by agricultural expansion, pollution, urbanization, and deforestation is the largest cause of biodiversity loss worldwide. Without their plant partners, fungal networks cannot survive. Logging, agriculture, and urbanization cause drastic disruption to the structure and physical integrity of underground fungal networks. This impairs their ability to sequester carbon, move nutrients, and promote soil aggregation.
Protecting the underground from cropland expansion could save the release of 41 billion tons of CO2 over the next 30 years – eight times the annual CO2 emissions of the USA.
When habitats are destroyed, the fungal community structure is dramatically altered because of shifts in local microclimate, loss of plant partners, and massive increases in soil erosion. The damage can take decades to recover.
The loss of grasslands and forests is of particular concern. Grasslands contain 20-30% of the world’s soil carbon, largely thanks to many trillions of kilometres of fungal networks that actively pull carbon into deep soil layers under grass roots. Globally, the total length of fungal mycelium in the top ten centimeters of soil is more than 450 quadrillion kilometres: around half the width of our galaxy.
Chemical-intensive farming also degrades the fungal networks that support plant growth. A 2019 study found the abundance of fungal networks was higher in organically-managed fields, and the fungal communities were far more complex: 27 species of fungi were identified as highly connected, or “keystone species,” compared with none in the conventionally managed fields. Application of fungicides further impairs fungal networks, reducing phosphorus uptake in croplands by more than 40%.
Confocal 3D-image of a fungal network with reproductive spores containing nuclei (smaller dots) | Image: ©Vasilis Kokkoris
SPUN says current trends suggest that more than 90% of the earth’s soil will be degraded by 2050. Protecting the underground from cropland expansion could save the release of 41 billion tons of CO2 from soil stocks over the next 30 years, equal to eight times the annual CO2 emissions of the USA.
Using 10,000 observations from the GlobalFungi dataset, coupled with hundreds of layers of global environmental data, SPUN is using machine learning to predict the distribution of network biodiversity across the planet. They will collect an additional 10,000 samples across ecosystems on all continents over the next 18 months to explore network biodiversity and carbon-sequestration hotspots. Together with striking new visualizations of nutrient flows inside networks, these maps will be used to identify high priority sites with the potential to store more carbon and survive extreme climate events.
Confocal 3D-image of a fungal network with reproductive spores containing nuclei (smaller dots) | Image: ©Vasilis Kokkoris
