Spatiotemporal Analysis of Vegetation Dynamics and Drought Stress in North East Nigeria Using MODIS Time-Series Data

Vegetation productivity in North East Nigeria is sensitive to inter-annual rainfall variability and progressive aridification, making spatiotemporal monitoring critical for early warning of ecological degradation. This study analysed vegetation dynamics and drought stress across Borno, Yobe, and Adamawa States using MODIS satellite time-series data spanning 2001 to 2023. The Normalised Difference Vegetation Index and Enhanced Vegetation Index products were analysed for temporal trends, seasonal phenology shifts, and anomaly detection. The Vegetation Condition Index was derived and correlated with standardised precipitation evapotranspiration index values to isolate drought-driven vegetation stress from land management effects. Mann-Kendall trend tests and Sen's slope estimator were applied to detect significant long-term changes in vegetation productivity. Results revealed statistically significant declining vegetation productivity trends in 38 percent of the study area, concentrated in areas experiencing both prolonged drought periods and elevated human pressure. Phenological analysis showed advancement of the start of the growing season by an average of nine days over the study period, suggesting altered rainfall seasonality. Severe vegetation stress anomalies coincided with documented drought years of 2010, 2017, and 2021. The study distinguishes climate-driven from human-driven vegetation decline and provides a spatially explicit analytical framework for targeting land restoration interventions in the most degraded zones of North East Nigeria. Keywords: vegetation dynamics, MODIS, drought stress, North East Nigeria, remote sensing.