Certain fig trees have the ability to transform significant quantities of carbon dioxide into solid forms, allowing carbon to remain in the soil even after the tree has perished. This indicates that fig trees used for timber or fruit cultivation could offer additional environmental benefits through this carbon sequestration process.

While all trees generally utilize carbon dioxide from the air, most of it is converted into structural molecules such as cellulose. However, some tree species also synthesize a crystalline substance known as calcium oxalate, and the bacteria within the trees and soil can convert it to calcium carbonate, a primary component of rocks like limestone and chalk.

Mineral carbon can remain in the soil significantly longer than organic matter derived from wood. Trees that store carbon in this manner include iron syrup (Milisia Excelsa), which is found in tropical Africa and is valued for its wood yet does not yield edible fruit.

Recently, Mike Rory from the University of Zurich and his team discovered that three fig species indigenous to Samburu County, Kenya, can also produce calcium carbonate through their own processes.

“Most trees generate calcium carbonate within the soil,” Laurie explains. “We [also] observe that high concentrations can transform the entire root structure into calcium carbonate in the soil, which is a remarkable finding.”

The research team initially identified the calcium carbonate-generating fig species by using a weak hydrochloric acid solution to detect its release from calcium carbonate. Subsequently, they could confirm the presence of calcium carbonate in the surrounding soil and analyze wood samples to pinpoint where calcium carbonate was being generated.

“What genuinely astonished me was how deep I was digging for [calcium carbonate],” Laurie remarked, as he presented his findings at the Goldschmidt conference in Prague, Czech Republic, this week.

Further investigations are needed to estimate the total carbon storage of these trees, the resilience of water in various climates, and the water requirement. Nevertheless, if fig trees can be integrated into future planting initiatives, they could serve as both a source of nourishment and a carbon sink, according to Laurie.