Small tradeoffs between social equity and conservation outcomes in a freshwater payment for ecosystem services scheme

Conservation programs around the world aim to balance social equity, economic efficiency, and conservation outcomes. Tradeoffs among these three objectives necessarily exist but have been quantified in only a handful of systems. Here, we use a multi-objective mathematical optimization model in a large, water-limited river basin to quantify these tradeoffs in a freshwater payment for ecosystem services (PES) program aimed at establishing environmental flows (e-flows). Across a range of budgetary and future climate scenarios, we find that tradeoffs between social equity and conservation outcomes are small. We also show that payment schemes in which incentives are allocated to a single water use sector are much less cost-effective than schemes in which incentives are allocated among multiple sectors. Thus, allocating payments equally among agricultural, municipal, and industrial sectors can be both more equitable and more cost-effective. Overall, our results illustrate how some carefully designed conservation programs may be able to achieve a triple bottom line of social equity, economic efficiency, and conservation effectiveness.