Quantifying land cover sensitivity to desertification in northern Nigeria's ecotones using an AHP-weighted MEDALUS model

Land degradation and desertification pose significant threats to ecosystem stability in dryland regions, particularly across the Guinea, Sudan, and Sahel ecotones of Northern Nigeria. This study develops an integrated indicator-based framework to quantify spatial and temporal patterns of environmental sensitivity from 2004 to 2024 using a modified Mediterranean Desertification and Land Use (MEDALUS) model. Climatic, vegetation, and soil indicators were weighted using the Analytic Hierarchy Process (AHP) to improve objectivity and reproducibility. Temporal trends were assessed using the Mann-Kendall test and Sen's slope estimator, while spatial patterns and clusters were identified using Local Moran's I. The Environmental Sensitivity Area Index (ESAI) reveals that the Guinea (mean = 2.60) and Sudan (2.57) savannahs exhibit higher sensitivity than the Sahel (2.43). Notably, vegetation decline is significant in the Guinea savannah, whereas the Sahel shows localized greening trends. Hotspot analysis indicates clustered high sensitivity in the Guinea and Sudan ecotones, contrasting with cold spots in the Sahel. Model validation using field-based climatic and soil data shows strong agreement with remote sensing outputs (R 2 ≈ 0.84), supporting the reliability of the indicators. The results challenge the conventional northward gradient of desertification and highlight the increasing vulnerability of transitional ecotones. This study provides a robust, transferable framework for environmental sensitivity assessment and supports targeted land management and policy interventions in dryland ecosystems.