Intra-growing season dry-wet spell pattern is a pivotal driver of maize yield variability in sub-Saharan Africa.

Climate variability plays a crucial role in the annual fluctuations of crop yields, posing a substantial threat to food security. Maize, the main cereal in sub-Saharan Africa, has shown varied yield trends during increasingly warmer growing seasons. Here we explore how sub-seasonal dry-wet spell patterns contribute to this variability, considering the spatial heterogeneity of crop responses, to map weather-related risks at a regional level. Our results show that shifts in specific dry-wet spell patterns across growth stages influence maize yield fluctuations in sub-Saharan Africa, explaining up to 50-60% of the interannual variation, which doubles that explained by mean changes in precipitation and temperature (30-35%). Precipitation primarily drives the onset of dry spells, while the influence of temperature increases with event intensity and peaks at the start of the growing season. Our large-scale, data-limited analysis approach has the potential to inform climate-smart agriculture in developing regions.

Global Water Challenges in Sub-Saharan Africa and how to strengthen science-policy dialogues on transboundary governance and cooperation.

The United Nations Water Conference 2023 highlighted the need for concrete actions to boost integrated water resources management for achieving the Sustainable Development Goals and called for strategies to enhance cooperation among stakeholders. Technical cooperation between countries and institutions in transboundary systems, e.g., on environmental data collection, is an effective way to promote international diplomacy and prevent disputes between riparian states. Still, establishing collaborations to inform bilateral dialogues on the identification of environmental challenges, their causes, and development priorities may be a difficult task in itself. This is particularly true in the African context because of limited resources and lack of data. In this paper, we analyse the case of nine transboundary river basins in Sub-Saharan Africa to identify which water-management challenges are perceived as most important by the different riparian countries from a policy and scientific perspective. Our insights are based on the most up-to-date scientific papers, open access reports and technical literature, river basin authority's strategy papers, projects' summary reports, and national policy documents. We also complement these sources with the pieces of information we gained through collaborations with regional and local experts, and management bodies (such as river basin authorities). We highlight the current water-related conflicts and the gap between the priorities identified by the scientific community and different riparian countries on how to tackle hydro-climatic change and improve food and energy security, human and environmental health. Based on our experience, we discuss some keys to building trust among stakeholders, strengthening cooperation, and identifying shared water-governance measures in transboundary river basins. They are: (i) connect science and policy to provide sound knowledge for the right questions, (ii) value local knowledge and exploit the complementarity of different perspectives, (iii) consider multiple spatial scales and multi-level stakeholders to leave no one behind, (iv) promote a culture which values trade-offs and handles complexity, and (v) co-create data and knowledge to facilitate stakeholder dialogue from problem definition to intervention identification.