Swiss researchers have discovered that the soils of tropical forests can store in a sustainable way large amounts of CO2 in the form of limestone. Some trees rooted in mineral soil that contains calcium store large quantities in the form of calcium oxalate crystals. During the decomposition of the tree and through a complex chemical reaction involving bacteria, these crystals are processed into limestone. Such is the case with the much logged Iroko tree that has the ability to accumulate mineral carbon such as calcium carbonate.
Normally, biomass does not store the CO2 as a transitional measure as it is returned in the process of decomposition, but limestone has a staying time that may reach a million years. This is an additional argument for the preservation and sustainable management of tropical forests to fight against the greenhouse effect.
Several species, present in both Africa and the Amazon, are able to contribute to this transformation. In contrast, limestone is naturally present in soil in temperate climates, and these trees get the calcium they need and then return it, giving a zero balance in terms of sustainable storage of CO2.