Remote Sensing Assessment of Mangrove Forest Health and Recovery Following Oil Spill Events in Ondo State

Mangrove forests in Ondo State's coastal zone have been subjected to oil spill impacts from both offshore pipeline incidents and onshore flow station leaks, generating documented vegetation mortality and ecosystem degradation. Natural recovery trajectories and the contribution of active restoration interventions to mangrove health restoration have not been empirically quantified for this coastline. This study assesses mangrove forest health and recovery dynamics in Ondo State's coastal zone following documented oil spill events using multi-temporal remote sensing analysis combined with field validation. Landsat-8 and Sentinel-2 time series data spanning 2014 to 2024 were processed to compute mangrove-specific spectral indices including the Red Edge Chlorophyll Index and Mangrove Quality Index at annual intervals. Field calibration involved canopy cover, tree density, and soil hydrocarbon measurements at 48 sample plots spanning spill-affected, recovering, and reference conditions. Trajectory analysis distinguishes progressive recovery sites from those exhibiting continued degradation or recovery arrest. Results indicate that spill-affected mangroves demonstrate three distinct recovery pathway types: complete recovery to reference condition within seven to nine years at low-severity sites, partial recovery with altered species composition at moderate-severity sites, and persistent degradation at severe spill sites where soil hydrocarbon concentrations remain above biological impact thresholds. Active replanting initiatives show modest positive effects on canopy recovery speed where soil conditions are not severely contaminated. The study provides spectral health indices and trajectory thresholds applicable to regulatory monitoring requirements for the Ondo State coastline. Recommendations address integration of satellite monitoring into the Joint Investigation Visit spill assessment process and targeting of active restoration to recovery-arrested sites. Keywords: mangrove health, remote sensing, oil spill recovery, Ondo State, coastal ecosystem restoration.