Remote Sensing Assessment of Forest Degradation in Anambra-Imo River Basin Forest Reserves

Forest degradation, defined as the loss of forest biomass, structure, and biodiversity without complete conversion to non-forest land use, is increasingly recognized as a biodiversity threat of comparable magnitude to deforestation. In the Anambra-Imo River Basin forest reserves spanning Anambra and Imo States in Nigeria's South East geopolitical zone, selective logging, fuelwood extraction, and agricultural encroachment drive progressive degradation that may not be captured by conventional deforestation assessments. This study applies a multi-temporal remote sensing analysis framework to detect and characterize forest degradation in the basin's main forest reserves between 2010 and 2023. Landsat and Sentinel-2 imagery were processed to calculate time-series of the Normalized Difference Vegetation Index, canopy fraction, and forest canopy height estimates derived from GEDI satellite data. Degradation severity scores were calculated for each pixel based on the trajectory of canopy cover change. Results identify that 38 percent of reserve forest area shows evidence of moderate to severe degradation, significantly exceeding the 12 percent classified as completely deforested. Spatial analysis reveals degradation hotspots concentrated along reserve access roads and stream valleys, consistent with logging route and fuelwood collection patterns. The study proposes a degradation early warning system based on automated monthly analysis of Sentinel-2 imagery, enabling rapid response by forest management authorities. Keywords: forest degradation, remote sensing, Anambra-Imo Basin, South East Nigeria, tropical forest