Fungi Stores a Third of Carbon From Fossil Fuel Emissions, New Study Reveals

Mycorrhizal fungi have been supporting life on land for at least 450 million years by helping to supply plants with soil nutrients essential for growth. In recent years, scientists have found that in addition to forming symbiotic relationships with nearly all land plants, these fungi are important conduits to transport carbon into soil ecosystems. In a meta-analysis published June 5 in the journal Current Biology, scientists estimate that as much as 13.12 gigatons of carbon dioxide equivalents (CO2e) fixed by terrestrial plants is allocated to mycorrhizal fungi annually — roughly equivalent to 36% of yearly global fossil fuel emissions. Because 70% to 90% of land plants form symbiotic relationships with mycorrhizal fungi, researchers have long surmised that there must be a large amount of carbon moving into the soil through their networks.

Mycorrhizal fungi transfer mineral nutrients to and obtain carbon from their plant partners. These bi-directional exchanges are made possible by associations between fungal mycelium, the thread-like filamentous networks that make up the bulk of fungal biomass, and plant roots. Once transported underground, carbon is used by mycorrhizal fungi to grow a more extensive mycelium, helping them to explore the soil. It is also bound up in soil by the sticky compounds exuded by the fungi and can remain underground in the form of fungal necromass, which functions as a structural scaffold for soils. The scientists know that carbon is flowing through fungi, but how long it stays there remains unclear.

The paper is part of a global push to understand the role that fungi play in Earth’s ecosystems. “We know that mycorrhizal fungi are vitally important ecosystem engineers, but they are invisible,” says senior author Toby Kiers, a professor of evolutionary biology at Vrije University Amsterdam and co-founder of the Society for the Protection of Underground Networks (SPUN). “Mycorrhizal fungi lie at the base of the food webs that support much of life on Earth, but we are just starting to understand how they actually work. There’s still so much to learn.” But there’s a race against time to understand and protect these fungi. The UN Food and Agriculture Organization warns that 90% of soils could be degraded by 2050, and fungi are left out of most conservation and environmental policy. Without the fertility and structure that soil provides, the productivity of both natural and crop plants will rapidly decline.