Coastal Wetland Carbon Stock Estimation in Niger Delta Mangroves, Delta State

Mangrove ecosystems in the Niger Delta are among the largest carbon sinks in West Africa, yet their carbon stocks remain poorly quantified at the landscape scale, limiting Nigeria's blue carbon accounting capacity. This study estimates above-ground, below-ground, and soil organic carbon stocks in mangrove wetlands along a 40-kilometre coastline in Delta State, South South Nigeria, using a combination of field inventory and remote sensing methods. Forty circular inventory plots of 25-metre radius are established across four mangrove forest types: Rhizophora-dominated, Avicennia-dominated, mixed species, and degraded regrowth zones. Tree diameter at breast height, height, and species identity are recorded and used with published allometric equations to compute above-ground biomass and carbon mass. Below-ground biomass is estimated using species-specific root-to-shoot ratios. Sediment cores to one-metre depth are collected for loss-on-ignition organic carbon analysis at 10-centimetre intervals. Above-ground carbon is spatially extrapolated using Sentinel-2 derived canopy height and NDVI relationships. Total ecosystem carbon stocks are expressed in tonnes of carbon dioxide equivalent per hectare. Findings are expected to demonstrate significantly higher carbon stocks in intact tall Rhizophora stands relative to degraded or secondary regrowth zones. The study provides data for Nigeria's Nationally Determined Contribution reporting on blue carbon and recommends mangrove restoration for carbon credit generation. Keywords: mangrove carbon stocks, blue carbon, Niger Delta, biomass estimation, Delta State