Fig trees may benefit climate by turning carbon dioxide into stone

Some carbon dioxide absorbed by fig trees gets turned into calcium carbonate within the wood and the surrounding soil, ensuring that the carbon is kept out of the air for longer

By Alex Wilkins

6 July 2025

Fig trees may be especially good at removing carbon dioxide from the atmosphere

Raimund Linke/mauritius images GmbH/Alamy

Some fig trees can convert surprisingly large amounts of carbon dioxide into stone, ensuring that the carbon remains in the soil long after the tree has died. This means that fig trees planted for forestry or their fruit could offer additional climate benefits through this carbon-sequestration process.

All trees take up CO2 from the air, and most of that carbon typically ends up as structural molecules used to build the plant, such as cellulose. Some trees, however, convert CO2 into a crystal compound called calcium oxalate, which bacteria in the tree and the soil can then convert to calcium carbonate, the main component of stones like limestone and chalk.

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Carbon in mineral form can stay within soil for much longer than it can in the tree’s organic matter. The trees known to store carbon in this way include the iroko tree , which grows in tropical Africa and is used for timber, but does not produce food.

Now, Mike Rowley at the University of Zurich in Switzerland and his colleagues have found that three species of fig tree native to Samburu County in Kenya can also make calcium carbonate from CO2.

“A large part of the trees becomes calcium carbonate above ground,” says Rowley. “We [also] see entire root structures that have pretty much turned to calcium carbonate in the soil where it shouldn’t be, in high concentrations.”