If we want to tackle the climate crisis, we need to address a global blindspot: the underground networks that sequester carbon and sustain life on Earth.
Fungi are invisible. Most of the time, mycelium live as branching. The total length of mycelium in the top 10 cm of soil is 450 quadrillion km, which is half the width of the universe. One of the wonders of the living world is the ancient life-support system that is comprised of these symbiotic networks.
About 25% of the planet's species live underground, where carbon floods into the soil and supports intricate food webs. 75% of the carbon is in the soil, making it a stable store. Climate change strategies and restoration efforts overlook fungi. Climate change and biodiversity loss can be caused by the destruction of underground fungal networks. These networks should be considered a global public good to be mapped, protected and restored.
The base of the food webs are the Fungi. For tens of millions of years, mycelium served as a plant root system for aquatic plants and was used to move them on to land. The evolution of plant-fungal partnerships resulted in a reduction in the level of atmospheric carbon dioxide. Plants depend on mycorrhizal fungi, a type ofycorrhizal fungi, which weave themselves through roots, providing plants with vital nutrients, defend them from disease and link them in shared networks. Plants are more important than leaves, wood, fruit, flowers or even roots.
The planet is being destroyed at an alarming rate. By the year 2050, more than 90% of the Earth's soil will be degraded. The life in the soil has not been taken into account by modern industries. Despite the fact that mycorrhizal fungi supply 80% of a plant's nutrition, intensive farming practices such as plowing and application of pesticides and chemical fertilisers severely reduce the abundance, diversity and physical integrity of the network. Logging causes havoc below ground, decreasing the abundance of mycorrhizal fungi and the diversity of fungal communities. A large study published in the fall of 2018 suggested that the health of trees across Europe was in danger due to nitrogen pollution from fossil fuel combustion and agricultural fertiliser.
A third and a half of the living mass of soils is made up ofycorrhizal fungal networks. We sabotage our efforts to limit global heating when we destroy them. Plants supply carbon to theirycorrhizal partners in exchange for nitrogen and phosphorus, which is what makes up the DNA in your own body. Plants and fungi engage in complex trading strategies in their exchange. The influence of these decisions spills over the whole world.
At least 5 billion tons of carbon dioxide are sequestered within mycorrhizal networks each year, which is roughly equivalent to 17 billion tons of carbon dioxide emissions in the US. The release of just a small amount of carbon from Europe's soils is equal to the annual emissions from 100m cars.
The health and resilience of the organisms on which we depend is at risk when we disrupt Mycorrhizal fungi. The soil is held together by a sticky living seam caused by the removal of the fungi. Mycorrhizal networks increase the amount of water that the soil can absorb, which in turn reduces the amount of soil resources that are lost to precipitation. They make plants more resistant to heavy metals. They boost the ability of plants to fight off pests by stimulating the production of defensive chemicals. The current focus on aboveground biodiversity neglects more than half of the most biodiverse underground ecosystems, because areas with the highest biodiversity aboveground are not always those with the highest soil biodiversity.
Clean air and water should be considered a global public good. In many parts of the world, traditional farming and land management practices have supported the health of the soil. Over the course of the 20th century, our behavior has led to trouble.
The Society for the Protection of Underground Networks, the Fungi Foundation, and GlobalFungi are some of the organizations that are advocating for soil ecology. These maps will help chart the properties of underground ecosystems, such as carbon sequestration hotspots, and document new species able to survive high temperatures and low precipitation. As the distribution of fungal networks shift in response to changing climates and land use, researchers will be able to track them, like they already do for global vegetation, climates and ocean currents.
A deeper knowledge of these dynamic living systems will support policies that aim to halt their destruction and encourage their recovery, as well as driving much-needed innovation in underground ecology.
Mycorrhizal networks have enriched life on our planet. They need the attention they deserve.
