Application of Remote Sensing for Monitoring Vegetation Cover Degradation in the Sahel Zone of Yobe State

Vegetation degradation in the Nigerian Sahel is an ongoing environmental crisis with severe implications for livelihoods, food security, and climate resilience in the North East geopolitical zone. This study applies remote sensing techniques to monitor temporal changes in vegetation cover in Yobe State between 2018 and 2024, using Normalised Difference Vegetation Index computed from Landsat 8 Operational Land Imager imagery. Time-series NDVI analysis is conducted for the pre-growing, peak-growing, and post-harvest seasons to capture intra-annual variability and long-term trends. Change detection is performed using differencing and thresholding approaches, and the spatial extent of severe degradation is mapped at the Local Government Area level. Results indicate a statistically significant decline in mean NDVI values across nine of the seventeen Local Government Areas examined, with the most severe degradation concentrated in the Nguru, Machina, and Yunusari LGAs. Rainfall data from the Nigerian Meteorological Agency are integrated into the analysis to differentiate climate-induced from anthropogenic drivers of vegetation loss. The findings suggest that overgrazing and encroachment of agricultural activities into fragile dryland ecosystems are major contributing factors beyond rainfall variability alone. The study provides spatial intelligence to support the Great Green Wall initiative and informs the Yobe State Ministry of Environment's desertification control programmes. Keywords: remote sensing, NDVI, vegetation degradation, Sahel, Yobe State.