Figs can help with the climate crisis: turning carbon dioxide into rock.

They're the Midas of the environment. But instead of gold, they transform it into rock. These are some species of fig trees with surprising abilities that could represent a valuable tool in the fight against climate change. This was revealed by an international research team that discovered how these trees can absorb carbon dioxide from the atmosphere and store it in the form of calcium carbonate "rocks ." The research was presented at the Goldschmidt 2025 Conference, the world's most important geochemistry conference, currently underway in Prague.

Absorb carbon dioxide

All trees, including fig trees, use photosynthesis to absorb carbon dioxide from the atmosphere and convert it into organic carbon for the growth of their trunk, branches, leaves, and roots, a process that reduces the amount of carbon in the air. For this very reason, trees are considered a potential means of mitigating emissions of this greenhouse gas. Some tree species, however, use carbon dioxide to produce calcium oxalate crystals, which are then converted by specific bacteria into calcium carbonate , the same mineral as limestone or chalk. Carbon in mineral form, however, can remain in the soil much longer than it can in the tree's organic matter, making this method more effective for storing carbon dioxide.

Food and carbon dioxide

Most research on this ability, also known as the oxalate-carbonate pathway , has focused on non-fruit trees. Among these is Milicia excelsa, a tree that grows in tropical Africa, is used for timber, and can store up to a ton of calcium carbonate over its lifetime. "We've known about this pathway for a long time, but its potential hasn't been fully explored," commented Mike Rowley, one of the study's authors. "If we plant trees for agroforestry and their ability to store CO2 as organic carbon while also producing food, we might choose trees that offer the added benefit of also sequestering inorganic carbon, in the form of calcium carbonate."

The fig trees

Specifically, the researchers focused on three ficus species grown in Samburu County, Kenya , and found that they produced calcium carbonate from CO2, forming both on the surface of the trunks and deeper down, where entire root structures were essentially transformed into calcium carbonate in the soil. "As calcium carbonate forms, the soil around the tree becomes more alkaline," the expert explained. " Calcium carbonate forms both on the surface of the tree and within the wood structures, likely because microorganisms decompose surface crystals and penetrate deeper into the tree . This shows that inorganic carbon is being sequestered in the wood at a greater depth than previously thought." Of the three fig species examined, the scientists found that Ficus wakefieldii was the most effective at storing CO2 in the form of calcium carbonate.

Potential applications

The next step will be to evaluate this tree's suitability for agroforestry, measuring parameters such as water requirements, fruit yield, and its ability to store carbon dioxide under different conditions. If figs could one day be included in future reforestation projects, they could become both a food source and a carbon sink. "Calcium carbonate is easier to identify in drier environments. However, even in wetter environments, carbon can still be sequestered," Rowley commented. "The oxalate-carbonate pathway could represent a significant, yet unexplored, opportunity to help mitigate CO2 emissions when we plant trees for forestry or fruit."