Reconciling tradeoffs among hydropower, decarbonization, and freshwater biodiversity through carbon offsets

Alongside other renewable energy sources, hydropower features prominently in commitments to achieve Net Zero Emissions, which could put decarbonization and freshwater biodiversity conservation goals in conflict. Here, we use multi-objective optimization to quantify tradeoffs emerging among fish biodiversity, carbon emissions and hydropower expansion across 17 river basins where hydropower will proliferate under Net Zero commitments. Project portfolios minimizing biodiversity impacts can triple carbon emission intensities in comparison to low-carbon hydropower portfolios. While carbon-biodiversity tradeoffs are inevitable, offsetting emissions from biodiversity-centered planning would only cost 0.29 U$ MWh ^-1 , or 0.45% of the levelized cost of hydroelectricity. Our analysis uncovers an opportunity to leverage the carbon market to both minimize biodiversity impacts of hydropower proliferation and minimize emissions with little loss in economic competitivity. More broadly, we provide a framework to navigate the tradeoffs among multiple ecological, economic and societal goals that are ubiquitous across many pressing sustainability challenges.