Soil Erosion in Southwestern Niger: Biophysical Drivers, Anthropogenic Pressures and Pathways to Land Restoration

Abstract

Southwestern Niger, a densely settled corridor of the West African Sahel centred on the Niamey region, has become one of the most intensively studied landscapes for understanding dryland soil erosion. Four decades of hydrological monitoring, wind-tunnel and field experimentation, remote sensing and rural livelihood research have produced a substantial body of evidence on how wind erosion, surface crusting, water erosion and gully dynamics interact with rapid population growth, cropland expansion and the retreat of fallow and woodland cover. This review synthesises that evidence to characterise the principal erosive processes operating in the region, the land use and demographic forces that have intensified them since the mid-twentieth century, their consequences for crop productivity, groundwater recharge and river sediment loads, the indigenous and introduced soil, along with water conservation techniques that have been deployed in response. Particular attention is given to the coexistence of a regional vegetation "greening" trend with persistent and, in places, worsening local degradation, a paradox that has reshaped scientific and policy debate over the past two decades. The review further considers the institutional and socio-economic conditions that govern the adoption of conservation practices such as zaï, half-moons and Faidherbia albida-based parklands, and closes with an assessment of research and policy priorities, the principal conclusions to be drawn from the accumulated literature, and the limitations inherent in a narrative synthesis of fragmented and methodologically heterogeneous evidence.