Impact Assessment of Endogenous Land Restoration Techniques in the Sahel Using a Counterfactual Model: Case of the Urban Commune of Tagazar, Tillabéri, Southwest of Niger

Abstract

This study evaluates the impact of endogenous land restoration techniques, particularly on certain fundamental soil properties, namely bulk density, volumetric moisture, and texture. The urban commune of Tagazar in Niger, which served as the experimental field for the study, is located in the heart of the Sahel and is highly exposed to land degradation. The methodological approach used is quasi-experimental, based on a counterfactual model, by comparing plots treated with sylvopastoral bunds and forest half-moons on the one hand, and untreated control plots on the other, located on glacis and plateau sites. A significant improvement in the physical properties of the soil was observed following the treatment of the sites with these techniques. Indeed, bulk density decreased by an average of 0.23 g/cm³ on glacis and 0.22 g/cm³ on plateaus, indicating improved porosity and soil structure. At the same time, volumetric moisture increased by 6.4% and 5.1%, respectively, in the two  environments, reflecting better soil water retention capacity. These effects are statistically significant (p < 0.05). As for the soil textural analysis, it shows a clear improvement in soil structure in areas rehabilitated with half-moons and bunds, with a reduction in sand content and an enrichment in silt and clay, especially at depth (10–30 cm). These results thus confirm the effectiveness of these land and water restoration and conservation techniques through the improvement of the soil’s hydrophysical function. They are particularly valuable for strengthening the resilience of Sahelian agroecosystems due to their simplicity, low cost, and adaptability to the local agroecological context.