Climate Refugees or Ecological Engineers? A Theoretical Investigation of Pastoral Migration and Biodiversity in Nigerian Dryland Landscapes

The relationship between pastoralist cattle migration and biodiversity in Nigerian dryland and semi-arid landscapes is contested, with dominant policy narratives characterizing pastoralists as ecological refugees whose mobility degrades biodiversity, contrasting with emerging evidence of complex interactions in which grazing can function as an ecological engineering process. This dissertation develops an original theoretical framework synthesizing pastoral mobility theory, dryland ecology, and ecological engineering concepts to investigate the biodiversity impacts of pastoralist migration across Nigerian dryland landscapes in Sokoto, Zamfara, Katsina, and Borno States, representing the North West and North East geopolitical zones. The framework is empirically tested through a comparative landscape ecology study analyzing vegetation diversity, soil invertebrate communities, and bird diversity across a gradient of pastoral use intensity at 80 sites. Long-term remote sensing vegetation time-series data are used to examine the effect of pastoral corridors on landscape heterogeneity and vegetation recovery dynamics. Results challenge the unidirectional degradation narrative by demonstrating that intermediate pastoral use intensity is associated with significantly higher grass species diversity and invertebrate richness compared to both unused and heavily grazed sites, consistent with the intermediate disturbance hypothesis. Original theoretical contributions include a revised pastoral-biodiversity interaction model that incorporates non-equilibrium dynamics and scale dependency. Policy recommendations target spatially adaptive pastoral governance frameworks that can accommodate ecological variability. Keywords: pastoral migration, dryland biodiversity, Nigeria, ecological engineering, non-equilibrium ecology