Abstract
Proposed hydropower dams at more than 350 sites throughout the Amazon require strategic evaluation of trade-offs between the numerous ecosystem services provided by Earth’s largest and most biodiverse river basin. These services are spatially variable, hence collective impacts of newly built dams depend strongly on their configuration. We use multiobjective optimization to identify portfolios of sites that simultaneously minimize impacts on river flow, river connectivity, sediment transport, fish diversity, and greenhouse gas emissions while achieving energy production goals. We find that uncoordinated, dam-by-dam hydropower expansion has resulted in forgone ecosystem service benefits. Minimizing further damage from hydropower development requires considering diverse environmental impacts across the entire basin, as well as cooperation among Amazonian nations. Our findings offer a transferable model for the evaluation of hydropower expansion in transboundary basins. , Planning for Amazonian hydropower Hydropower projects are proliferating in many parts of the world. The benefits they bring in electricity supply are often offset by environmental costs. In an international collaboration, Flecker et al . present a study that aims to optimize the retention of ecosystem services in the face of hydropower expansion in the Amazon basin (see the Perspective by Holtgrieve and Arias). The authors found that simultaneous consideration of multiple criteria (sediment transport, river connectivity, flow regulation, fish biodiversity, and greenhouse gas emissions) is necessary for optimizing the size and location of dams, and that the geographical scale of planning is also key (benefits from a smaller-scale plan may be detrimental at the basin scale). Their computational method allows the evaluation of each trade-off individually or all trade-offs simultaneously and is broadly applicable in other basin settings. —AMS , Computational advances reveal opportunities for more sustainable hydropower development in large transboundary river basins.