Cultivation of diverse crop species and varieties support yield stability in smallholder farming system

Rising climatic variability worsen smallholders' food insecurity through greater year-to-year yield fluctuations. Although crop diversification is widely promoted as an adaptation strategy to climate change, its capacity to stabilize yields under real farm management remains poorly understood. Drawing on a five-year monitoring program of 33 farms in a semi-arid agroecosystem in Senegal, we tested whether crop diversity at both species and varietal levels stabilizes climate-driven yield fluctuations, and identified the underlying mechanisms. Our results show that farmers growing higher crop species and varietal diversities show significantly higher total yield stability under high climatic variability.

Higher crop diversity reduces inter-annual variation without affecting mean yields. Two mechanisms drive the stabilization effect of crop diversity, with distinct contributions from species and varietal levels, respectively. First, pearl millet that occupy the largest share of cropland locally, exhibits the most stable yields, thereby anchoring overall portfolio stability through a selection effect. Second, asynchronous yield fluctuations among individual crops -more pronounced among varieties of cereals -buffer each other, therefore providing an insurance effect. Our assessment of the crop diversity-yield stability relationship is unique in being grounded in real, on-farm data from the Global South. Beyond contributing to the dynamic field of agroecology, this study offers new insights into the identity of crops and complementarity mechanisms that farmers could leverage to enhance yield stability using the present crop portfolio.