Hidden fungi absorb over a third of Earth’s fossil fuel emissions, new study discovers

Powerful relationships hidden in our soil are helping to store away some of humanity's carbon emissions – and could help us lock away even more if we protect them, according to a new study.

Researchers from the UK, South Africa and the Netherlands have revealed that each year plants pull 13.12 gigatons of carbon dioxide equivalents (CO₂e) from the atmosphere into a certain type of fungi, known as mycorrhizal fungi, found in the soil. That’s equivalent to a whopping 36 per cent of annual global fossil fuel emissions.

Mycorrhizal fungi form mutually beneficial partnerships – known as symbiotic relationships – with the roots of plants. The fungi supply the plants with nutrients that are essential for the plant’s growth and, in return, take some of the sugars that the plants produce through photosynthesis,as well as their carbon dioxide.

“This research has given us an awareness of the potential role that these fungi play in controlling rising CO₂ levels,” author Dr Heidi Hawkins, research associate on plant-soil-microbe interactions at the University of Cape Town, South Africa, told BBC Science Focus.

“Understandably, much focus has been placed on protecting and restoring forests as a natural way to mitigate climate change,” said Hawkins in a press release.

“But little attention has been paid to the fate of the vast amounts of carbon dioxide that are moved from the atmosphere during photosynthesis by those plants and sent belowground to mycorrhizal fungi.”

Scientists have known for a long time that these fungi form symbiotic relationships with plants, but only in recent years discovered that they also act as the gateway for carbon to enter the soil. The study published in Current Biology finally estimates what the figures are.

Mycorrhizal fungi transport nutrients and minerals through the soil using extensive, filamentous networks called mycelium. For some fungi, these networks sit underneath their fruiting bodies, known as mushrooms, which release spores to help the fungi reproduce.

Mycorrhizal fungi use carbon to expand their mycelial network. It also helps to build strength in the structure of soils. But the researchers still don’t know how long carbon stays in the fungi.

“While mycorrhizal fungi certainly contain and release carbon into the soil, we do not currently know whether mycorrhizal fungi are a carbon store (i.e. they maintain carbon) or sink (i.e. they increase carbon over time),” Hawkins told BBC Science Focus.

“That said, there are already some practical actions we can take by, for example, conserving areas where we know that those specific mycorrhizal associations result in a high allocation of carbon to the soil (forests and heathlands).”

The researchers emphasise the need for more research as the UN Food and Agriculture Organisation (FAO) warns that 90 per cent of soils could be degraded by 2050.

Co-author Merlin Sheldrake, who wrote Entangled Life: How Fungi Make Our Worlds, Change Our Minds And Shape Our Futures, said: “Many human activities destroy underground ecosystems. Besides limiting the destruction, we need to radically increase the rate of research.”