Carbon Storage and Sequestration by the Mangroves of the Lower Gangetic Delta

Mangrove ecosystems, noted for their exceptional carbon storage capabilities, serve as potent natural carbon sinks due to their unique morphological configuration. Mangroves on the intertidal zone capture sediment with their intricate root systems, and form deep anaerobic soils effective in trapping carbon. The chapter highlights the results of a 30-year research (1993–2022) programme in the Indian Sundarban region that assessed the carbon storage potential of five dominant major mangrove species under varying salinity conditions. Findings revealed that species like Sonneratia apetala, Avicennia marina, Avicennia alba, and Avicennia officinalis showed significant carbon sequestration potential in the age group 11–16 years, while Excoecaria agallocha excelled at 5–10 years. Lower to moderate salinity levels normally accelerate the magnitude of carbon sequestration. Mangrove substratum, with their organic-rich sediments, have a higher carbon sequestration capacity than terrestrial forests. Soil organic carbon (SOC) levels peaked during the monsoon due to runoff, sediment deposition, and increased litter fall. Analysis across 24 locations in the Indian Sundarban Biosphere Reserve indicated the western sector of the region with the highest SOC values due to significant human activities contributing organic matter. SOC stock analysis over a decade showed substantial increase during both premonsoon and monsoon seasons. However, estimating mangrove carbon storage remains challenging due to complex root systems, possibilities of man-animal conflict during the field study, technical limitations, and tidal influences, compounded by climate change impacts.