The rapid expansion of hydropower is a pressing issue confronting the world’s most biodiverse river systems. In the Amazon Basin, Earth’s largest river system, 165 dams have been built and more than 350 new dams have been proposed. While environmental assessments have considered individual dams, little attention has been paid to evaluating tradeoffs between energy generation and portfolios of ecosystem services for different configurations of dams across the river network. Assessing tradeoffs and cumulative effects of numerous dams in regions such as the Amazon is especially challenged by the scarcity of data, and the lack of computational tools for basin-scale analyses. Here we evaluate tradeoffs between hydropower generation and a set of supporting and regulating ecosystem services including hydrological flow regime, sediment and nutrient transport, and movement corridors that structure Amazon riverine ecosystems, in addition to environmental criteria such as greenhouse gas emissions. Our analysis harnesses new tools from the emerging field of computational sustainability based on a Pareto-optimality approach, which generates a Pareto frontier with sets of solutions (i.e., portfolios of dam configurations) optimizing across environmental objectives for all possible aggregate hydropower yields.
Results/Conclusions
Tracking historical trajectories of tradeoffs between hydropower generation and environmental impacts, we find that a history of uncoordinated planning has led to foregone opportunities to mitigate ecosystem service losses while achieving energy generation. Notably, we find that over the last decade, basin-wide network connectivity has sharply declined to almost 50% of its original unimpeded basin-wide connectivity. Moreover, optimal hydropower dam location choices based on single criteria contrast sharply with those considering multiple objectives. For example, some dams that are always contained in optimal solutions based on a single criterion such as connectivity, are never found in optimal solutions when a holistic suite of environmental criteria is considered. Finally, planning at different spatial scales can provide different outcomes with respect to the frequency of projects in optimal solutions. Clearly, planning for Amazon hydropower requires decision tools with adequate sophistication to navigate multiple tradeoffs between energy and a diversity of environmental criteria and ecosystem services.