Decoupling of vegetation from rainfall in Nigeria’s drylands under demographic pressure

Dryland degradation remains one of the most pressing environmental challenges, yet the balance between climatic and anthropogenic drivers remains contested. Using satellite-derived greenness (MODIS NDVI), rainfall (CHIRPS), cropland (MCD12Q1), population (GHSL-POP), and forest loss (Hansen GFC), we assessed vegetation change in Nigeria’s dryland (19 northern states of the federation) during 2000–2020. NDVI residual trends revealed widespread greenness decline, with rainfall–vegetation coupling negative but generally weak and inconsistent across accumulation lengths and lags. Pooled regression analysis indicated that rainfall trends were not a significant predictor of NDVI decline (β = − 0.013, p = 0.955). Instead, population growth emerged as the strongest correlate (Spearman r = 0.48, p = 0.037; standardized β = 0.473 ± 0.300, p = 0.115), while cropland expansion showed no detectable effect (β = 0.104, p = 0.820). Cumulative deforestation exceeded 13 million ha, showing land-use pressures despite limited explanatory power at the state scale. These findings highlighted the complexity of dryland degradation attribution, with demographic growth and deforestation exerting greater influence than rainfall variability.