Long-Term Trajectories of Land Degradation and Rehabilitation in Nigeria’s Afforestation Programme Areas: A Multi-Decadal Analysis

Nigeria's national afforestation and land rehabilitation programmes have invested substantial resources in addressing land degradation in the Sudan and Sahel savanna zones since the 1970s, yet the long-term ecological trajectories of programme areas and the factors governing rehabilitation success or failure have not been subjected to systematic multi-decadal analysis. This doctoral research analyses land degradation and rehabilitation trajectories across eleven major afforestation programme areas in Sokoto, Katsina, Kano, and Jigawa states over a 40-year period using an innovative combination of historical aerial photography, Landsat archive time series, field ecological surveys, and institutional history methods. Landsat normalised difference vegetation index trajectories spanning 1985 to 2024 are combined with historical aerial photograph interpretation for 1970-1980 baseline conditions to construct 40 to 50-year vegetation cover trajectories at each programme site. Field ecological surveys at 220 plots assess current vegetation composition, soil organic carbon, and biodiversity indicators as outcome measures. Institutional history reconstruction through 85 interviews with former programme managers, community elders, and current land management officials traces the governance pathways associated with different trajectory types. The study identifies three dominant trajectory types: sustained recovery, temporary recovery followed by reversal, and persistent degradation despite intervention. Governance pathway analysis reveals that community co-management transitions, even when informal, are the strongest predictor of sustained recovery outcomes, while programme discontinuity and absence of land tenure formalisation are associated with reversal trajectories. Theoretical contributions include a multi-decadal rehabilitation trajectory framework applicable to African dryland restoration programmes. Policy recommendations address long-term programme governance design and monitoring. Keywords: land rehabilitation, afforestation, long-term trajectories, dryland restoration, Northern Nigeria.