Effects of annual rainfall variability and agroecological practices on vegetation dynamics in Niger’s Sahelian zone

In recent years, the Sahel has experienced seasonal regreening, but the relative importance of environmental conditions and land management as drivers remains unclear. This study assesses the influence of rainfall variability and different agroecological interventions in a Sahelian zone of Niger from 2001 to 2025 by integrating rainfall data, Normalized Difference Vegetation Index (NDVI) analysis of satellite imagery, and data on agroecological practices from 70 intervention sites. On the regional scale, our results show a statistically significant positive trend in NDVI values, whereas annual rainfall did not show a significant monotonic trend but exhibited spatial heterogeneity. At the local scale, we used a Before-After-Control-Impact (BACI) design with 70 paired intervention and control sites to disentangle interventions effects from rainfall variability. The overall BACI effect was significant (0.072 ± 0.008, p = 0.001), with the strongest effect for Farmer-Managed Natural Regeneration (FMNR; 0.145 ± 0.021, p = 0.006). Agroecological interventions and regreening are strongly positively correlated (r = 0.64, p < 0.05), whereas the correlation between rainfall and regreening is weaker (r = 0.24, p < 0.05). Our findings suggest that agroecological interventions contribute to regreening trends in the selected region and may enhance the resilience of smallholder farmers to climate variability.