Spatio-temporal dynamics of biomass and carbon in the mangrove vegetation of Sofala bay between 2003, 2013, and 2023

Abstract

Biomass and carbon stored in vegetation are important indicators of its role in reducing greenhouse gases. Thus, this study aimed to evaluate the spatiotemporal dynamics of biomass and carbon stocks in mangroves, focusing on changes occurring in 2003, 2013, and 2023. To this end, field measurements conducted in the Sofala Bay mangroves in 2013 were used to quantify biomass and carbon per sampled plot. Moreover, the correlation between biomass and carbon in each 2013 plot and the reflectance of vegetation indices (NDVI, SAVI, and EVI) as well as the reflectance of blue, green, and red bands (independent variables) derived from 2013 satellite images was subsequently analysed. Linear regression models were tested and fitted to estimate biomass and carbon using independent variables derived from satellite imagery. The best models for estimating biomass and carbon used NDVI as the independent variable, with adjusted coefficients of determination (R²adj) of 0.83 and 0.78, and standard errors of the estimate (Sxy%) of 23% and 24% for biomass and carbon, respectively. Therefore, a decrease in biomass and carbon stocks was observed from 2003 to 2013 and from 2013 to 2023, with an annual loss rate of 0.8%. In terms of biomass and carbon density per hectare, areas with high density increased between 2003 and 2023, reaching 6 t/ha and 3 t/ha for biomass and carbon, respectively. The reduction in biomass and carbon stocks is associated with the loss of mangrove cover in Sofala Bay.

Keywords: Mangrove; Biomass; Carbon