Effects of shrimp aquaculture on mangrove soil carbon stocks and sustained-flux global warming potentials

Abstract

Mangroves provide a multitude of ecosystem services, including storing up to ca. 20 Pg of carbon. Aquaculture driven mangrove degradation results in significant carbon losses associated with forest clearance, drainage, and the removal of surface soils. However, uncertainties exist regarding the magnitude of loss due to environmental factors, land use, study type and aquacultural practices. Sustained-flux Global Warming Potentials (SGWP) during construction, operation and abandonment phases is understudied. Here we used a microcosm simulation in order to better constrain carbon loss pathways and SGWP, inform management practices and highlight knowledge gaps. Biogeochemical emissions during culture and abandonment added ca. 25%, suggesting the impact of aquaculture is underestimated. However, soil removal during construction dominated emissions (ca. 75%). Thus, long operation duration and re-use of ponds would reduce emission factors, and the fate of removed soils is suggested as a priority for research. Extrapolation suggests emissions could be important for national and regional carbon accounting, but also in relation to global climate mitigation, given the potential for significant underestimates of the impact of aquaculture on mangrove ecosystems.