Exploring the unintended consequences of climate change mitigation for African river basins

Global policies to mitigate climate change by pricing greenhouse gas emissions will have impacts across sectors down to the local scale that are often difficult to anticipate and are consequently overlooked in many analyses. This study addresses this gap by investigating how multisector dynamics across interconnected Water-Energy-Food (WEF) systems at the local scale are impacted by global climate change mitigation efforts. We use a detailed river basin-scale operational model of the Zambezi Watercourse in Southern Africa that enables the exploration of synergies, tradeoffs, and vulnerabilities for the WEF systems. Our analysis also contributes quantitative evidence of the unintended vulnerabilities that may emerge for this basin across a broad array of potential climate and socio-economic futures. To explore the uncertainty space, we adopt an exploratory modeling approach to project future irrigation demands by systematically sampling the Shared Socioeconomic Pathways components along with multiple Shared Policy Assumptions, which set a mitigation policy context including regional participation in mitigation efforts and the pricing of carbon emissions. We also bias-adjust climate projections from different combinations of global and regional climate models for different Representative Concentration Pathways to force local hydrological models and produce projections of water availability. Our results indicate that fragmented land-use change emissions policies can have negative side effects on local water demands, generating increased risks for failures across all the components of the WEF systems in the Zambezi Watercourse. Analogous vulnerabilities could impact many river basins in Southern and Western Africa, raising concerns about the disproportionate WEF impacts of these policies in African countries and the importance of coordination in ameliorating those impacts. It is critical to connect global climate change mitigation policies to local dynamics for a better exploration of the full range of possible future scenarios while supporting policy makers in prioritizing sustainable mitigation and adaptation solutions.