In semi-arid regions like the American Southwest, human exploitation of water resources may compromise the ability of riparian areas to supply other valuable ecosystem services. Understanding these tradeoffs is critical to sound environmental decision-making, but assessing the costs and benefits of alternative management scenarios is hampered because many important ecosystem services have not been assigned market values. Tools from ecological economics (e.g., non-market valuation methods) may be useful for quantifying the value of these services and hence for evaluating the costs and benefits of alternative courses of management. Ecological science can play an important role in this process, as predicting the effects of management actions on ecosystem services requires an understanding of how alterations to key ecological and hydrologic processes will affect riparian structure and function. As in many other interdisciplinary endeavors, communicating scientific findings across disciplinary boundaries and with the public are key challenges. Our session weaves together several key components and challenges to using science for valuing ecosystem services in semi-arid riparian systems. Interdisciplinary studies conducted on the San Pedro River (Arizona) and the Middle Rio Grande (New Mexico) form a core component of the session.