Fungi, the unsung heroes of the natural world, have now emerged as potentially key players in the fight against climate change; a new study, published in the journal Current Biology, reveals that mycorrhizal fungi, which have been supporting plant life on land for millions of years, are responsible for storing a significant amount of carbon from fossil fuel emissions — this finding could prove crucial in achieving global net-zero emissions targets.

The study estimates that mycorrhizal fungi allocate as much as 13.12 gigatons of carbon dioxide equivalents (CO2e) from terrestrial plants to soil ecosystems annually. To put this into perspective, it’s approximately 36% of the total global fossil fuel emissions released each year.

The significance lies in the fact that 70% to 90% of land plants form symbiotic relationships with these fungi, highlighting their potential as major conduits for carbon sequestration.

The vital role of fungi in Earth’s ecosystems

“We always suspected that we may have been overlooking a major carbon pool,” says Heidi Hawkins, one of the study’s authors. While efforts have primarily focused on protecting and restoring forests to combat climate change, little attention has been given to the fate of the vast amounts of carbon dioxide absorbed by plants during photosynthesis and transported underground to mycorrhizal fungi.

Mycorrhizal fungi facilitate the exchange of mineral nutrients with plant roots and obtain carbon in return. This bi-directional transfer occurs through the fungal mycelium, which forms intricate networks below the ground. Carbon absorbed by these fungi contributes to their growth and exploration of the soil.  Some carbon becomes bound in the soil through sticky compounds produced by the fungi, while the rest remains as fungal necromass, which provides structural support for the soil.

Although scientists acknowledge that carbon flows through these fungi, the duration of its storage remains uncertain. It is partly retained within mycorrhizal structures during the fungi’s lifespan and after their death. Some carbon decomposes into smaller molecules, binding to soil particles or being reused by plants. However, a portion is released as carbon dioxide through respiration by other microbes or the fungi itself.

Mycorrhizal fungi allocate as much as 13.12 gigatons of carbon dioxide equivalents (CO2e) from terrestrial plants to soil ecosystems annually. (Image: “Fungi – Orillia – Ontario – Canada –” by Onasill – Bill Badzo – 149 Million Views – Thank Y )

The study is part of a global effort to understand the vital role of fungi in Earth’s ecosystems. Toby Kiers, the senior author of the paper, emphasizes the importance of mycorrhizal fungi as ecosystem engineers, although their invisible nature makes them relatively understudied. With the escalating threat to soil fertility and structure due to degradation caused by human activities, the productivity of both natural and cultivated plants is at risk.

To address this challenge, organizations such as the Society for the Protection of Underground Networks (SPUN), the Fungi Foundation, and GlobalFungi are actively involved in mapping Earth’s fungal networks. These initiatives aim to highlight carbon sequestration hotspots, document resilient fungal species, and raise awareness about the critical role of fungi in maintaining ecosystem health and resilience.

While the study’s estimates are not definitive, they provide valuable insights into the carbon-storage potential of mycorrhizal fungi. Further empirical research is needed to better understand the intricate carbon and nutrient fluxes between plants and fungi. Protecting these underground ecosystems is imperative, not only for mitigating climate change but also for preserving the health of the planet’s interconnected ecosystems on which humanity depends.

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