Long-Term Assessment of Coastal Ecosystem Change in the Niger Delta Using Decadal Remote Sensing Archives

The Niger Delta's coastal ecosystems are among the most extensively altered tropical coastal environments globally, yet systematic decadal-scale remote sensing assessments of ecosystem change spanning multiple decades remain absent. This study conducts a long-term assessment of coastal ecosystem change in the Niger Delta from 1984 to 2023 using archived Landsat imagery across all available epochs. A harmonised land cover classification methodology is developed to ensure temporal consistency across sensor generations from Landsat 4 to Landsat 9. Land cover categories including primary mangrove, degraded mangrove, freshwater swamp forest, tidal mudflat, open water, agricultural land, and urban areas are mapped for nine epochs at 5-year intervals. Trajectory analysis using vegetation index time series characterises ecosystem state transitions, distinguishing between gradual degradation, abrupt disturbance, and recovery trajectories. Results document a net loss of 31 percent of primary mangrove cover and 44 percent of freshwater swamp forest since 1984, representing one of the most significant tropical coastal ecosystem losses in Africa. Causal attribution analysis partitions change drivers between oil infrastructure expansion, agricultural encroachment, and community settlement growth. Keywords: coastal ecosystem, Niger Delta, long-term remote sensing, mangrove, land cover change