Mapping Wetland Loss and Degradation in the Cross River Estuary, Cross River State

Estuarine wetlands provide critical ecosystem services including carbon sequestration, nursery habitat for commercially important fish species, and coastal storm buffering, yet these systems face accelerating loss from land reclamation, pollution, and hydrological modification. This study maps wetland loss and degradation in the Cross River Estuary, Cross River State, over the period 2013 to 2023 using multi-date Landsat and Sentinel satellite imagery. Supervised classification was applied to delineate mangrove, freshwater herbaceous wetland, tidal flat, and open water classes, and change matrices were computed to quantify class transitions. Field verification was conducted at 35 reference sites, and ecological condition was assessed using a rapid visual assessment protocol adapted for Nigerian estuarine conditions. Results indicate a net wetland loss of 18.7 percent over the study decade, with mangrove conversion to aquaculture ponds constituting the dominant change process in the lower estuary. Urban expansion around Calabar's waterfront accounts for significant freshwater wetland loss in the upper estuary. Degraded wetland areas exhibit reduced species diversity, elevated sediment heavy metal concentrations, and compromised nursery function as assessed by juvenile fish abundance transects. The study recommends strict enforcement of the Cross River State Mangrove Conservation and Protection Law, spatial designation of wetland conservation priority zones, and community-based mangrove replanting initiatives. Keywords: wetland loss, mangrove, Cross River Estuary, coastal ecosystem, land reclamation.