The Blue Carbon Engine
The Pichavaram mangrove forest, located between the Vellar and Coleroon estuaries in Tamil Nadu, is a site for "blue carbon" science. This term refers to the carbon captured and stored by coastal and marine ecosystems. Covering roughly 1,100 hectares (around 4,250 acres), this complex network of waterways, canals, and over 50 islands is one of the largest mangrove forests in India.
The forest's exceptional ability to sequester carbon dioxide is its primary feature for climate science. Studies at Pichavaram show carbon sequestration rates varying from 2.33 to 4.44 grams of carbon per square meter per year. The reason for this efficiency lies in the soil. The waterlogged, oxygen-poor mud traps organic matter—fallen leaves, branches, and roots—preventing it from decomposing and releasing carbon back into the atmosphere. This process locks carbon away for exceptionally long periods. The soil organic carbon stock in the upper 90 cm of a natural mangrove stand at Pichavaram has been measured at 146.1 megagrams of carbon per hectare. This subterranean storage is what makes coastal wetlands like Pichavaram so effective as long-term carbon sinks. The dominant tree species driving this process include Avicennia marina and several species of Rhizophora.