Re-greening the Sahel? Evaluating tree cover restoration strategies in Niger

Abstract

In the Sahel, land degradation caused by climate variability and unsustainable human activities has led to soil erosion, declining fertility, and worsening food insecurity. To address this, large-scale restoration initiatives incorporating soil and water conservation (SWC) techniques and drought-resistant tree species have been implemented. This study evaluated the growth of 1564 trees from six species (Acacia nilotica, Acacia raddiana, Senegalia senegal, Vachellia seyal, Bauhinia rufescens, and Ziziphus mauritiana) on rehabilitated lands, using a Bayesian growth model to assess the effects of SWC structures, management practices, and geomorphological conditions. Among the SWC techniques studied—half-moons, trenches, bench terraces, stone bunds, and trench-bund combinations—half-moons proved most effective in enhancing tree growth (+12 %). Pediments provided the best conditions for tree development, outperforming plateaus and slopes. The absence of site management (guarding, replanting, and maintenance of plants and structures) decreased growth (−9 %). Sustainable reforestation in the Sahel requires integrating scientific knowledge with local expertise, adaptive strategies, and community involvement. A holistic approach that prioritizes effective SWC structures, suitable planting sites, and continuous management is crucial for restoring degraded lands, strengthening ecosystem resilience, and ensuring long-term success.