Fungi Store Billions of Tonnes of Carbon

What's the problem we're trying to solve?

When we burn coal, oil, and gas for energy, we release carbon dioxide (CO2) into the air. Too much CO2 traps heat in our atmosphere and warms the planet. Scientists and leaders everywhere are asking: "How can we pull carbon out of the air and lock it away somewhere safe?" The answer might be growing right under our feet — in a hidden network of fungi in the soil.

How much carbon do fungi really store?

In 2023, scientists from universities across the UK and Europe published a big discovery in the journal Current Biology. They looked at hundreds of studies about soil and plants to figure out one question: "How much carbon do mycorrhizal fungi — fungi that partner with plant roots — actually move from the air into the soil?"

The answer was stunning. These fungi transfer about 13.12 billion tonnes of CO2 into the soil every single year. To understand how much that is, imagine a number so big you cannot count it. It's roughly one-third of all the CO2 we release every year by burning coal, oil, and petrol.

How do fungi store carbon?

Here's where the magic happens. Mycorrhizal fungi form partnerships with plant roots. The plant catches sunlight and turns it into sugar (that's photosynthesis). The plant then gives some of that sugar to the fungus. In return, the fungus gives the plant nutrients from the soil — especially nitrogen and phosphorus, which plants need to grow.

But here's the clever part: the fungus doesn't eat all the sugar right away. Instead, it builds long underground threads called hyphae and uses the sugar to grow them. These hyphae spread through the soil, and the carbon (from the sugar) gets locked into the fungal cells themselves.

Unlike bacteria, fungi are very good at holding onto carbon. Scientists say fungi have a "carbon use efficiency" of 40 to 55% — that means 40 to 55 out of every 100 pieces of carbon they take in, they keep in their bodies. The rest gets broken down for energy.

How long does the carbon stay buried?

This is perhaps the best part. The carbon doesn't just sit there for a year or two. It can stay locked in the soil for hundreds of years. As the oldest parts of the fungal threads (hyphae) die, they break down into humus — rich, dark organic matter that holds carbon for thousands of years.

Soil scientists measure how much fungal material is in healthy soil, and the amounts are enormous. In a single piece of soil the size of a marble, there can be miles of fungal threads woven together in an intricate network—so densely packed that the total hyphal length inside could stretch for many metres if you could straighten it all out. All that fungus, spread across the entire planet, is storing carbon on a scale that rivals what we do with any human-made technology.

Why haven't we heard about this before?

Before 2023, this huge carbon-storage system was almost invisible to climate scientists and policymakers. Professor Katie Field, who led the research at the University of Sheffield, said: "Mycorrhizal fungi represent a blind spot in carbon modelling."

Nobody was counting it. Nobody was measuring it. It was happening quietly in every forest, grassland, and garden soil, and nobody was talking about it.

What happens if we protect soil?

If we understand how important this fungal network is, we can make choices to protect it. Planting trees and plants, avoiding heavy pesticides (which kill fungi), and leaving soil undisturbed all help fungi do their job. When we protect the fungi in soil, we're protecting one of Earth's most powerful carbon-storage systems.

Safety first: Mycorrhizal fungi are not the kind of fungi you can see or eat. They live underground, invisible to our eyes, as microscopic threads in the soil. Never eat wild mushrooms — look, don't pick. The safe way to grow mushrooms is with a grow kit or to buy them from a shop, always with an adult.

The short version

Mycorrhizal fungi partner with plant roots and move carbon from the air into soil every single day. Scientists found that these fungi store about 13 billion tonnes of CO2 in soil every year — roughly a third of the carbon we emit from burning fossil fuels. This carbon can stay locked away for hundreds of years. Protecting soil means protecting one of our most powerful natural climate tools.