Fungal Networks Are a Crucial Global Carbon Pool

Many excellent studies on carbon flows in mycorrhizal fungi had been done, but until this study nobody had harmonized the data.

We found that 13 billion tons of carbon are cycled through fungal networks annually.

Our goal was to synthesize all the data currently out there to try and better understand the carbon cycling.

Mycorrhizal mycelium act as a global carbon pool.

We've known for quite some time that carbon flows from plants into mycorrhizal fungi. It’s one of the central pieces to this type of plant-fungal symbiosis. But until now, we haven't had a good global estimate of how much that flow of carbon is. There have been some back-of-the-envelope calculations and small-scale studies, but the numbers varied a lot. With this review, our goal was to synthesize all the data currently out there to try and better understand this overlooked component of the carbon cycle.

We know that mycorrhizal fungi are holding carbon. Plants photosynthesize using sunlight and carbon dioxide from the atmosphere and convert them into energy. During that process, the plants fix carbon – turning it from its gaseous form into organic carbon compounds. The plants then use this carbon to build their structures. Flowers, leaves, stems – those are all made from organic carbon compounds.

We looked primarily at three different types of mycorrhizal fungi – arbuscular, ectomycorrhizal, and ericoid, and were able to find that collectively, these three groups of fungi have 13.12 billion tons of carbon dioxide allocated to them every year.

To put this number in perspective: 13.12 billion tons of CO2 is about 36% of global fossil fuel emissions last year. China is by far the biggest emitter of greenhouse gasses – its annual emissions in 2021 were 12.47 billion tons. The U.S. emitted 4.75 billion tons of carbon dioxide in 2021 – mycorrhizal fungi take up nearly three times that each year.

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