Riparian ecosystems encompass a diverse suite of ecosystem types, including river banks, floodplains, and wetlands, that are characterized primarily by being ecotones, or transitional zones, between adjacent terrestrial and aquatic realms. In general, riparian ecosystems represent wetter, cooler, and more heterogeneous habitats than adjacent upland areas and consequently tend to support biologically distinctive, productive and diverse communities. Riparian ecosystems also provide a wealth of critical ecosystem functions and services of importance at local and catchment scales. In particular, riparian vegetation plays a key role in: regulating microclimates and water quality; preventing riverbank erosion and promoting landform stability; subsidizing aquatic and terrestrial food webs; and providing habitat for a wide range of aquatic, amphibious, and terrestrial organisms. Despite these values, riparian ecosystems are also some of the most altered, degraded and vulnerable ecosystems on Earth, due largely to their position in the landscape and hotspots of intensive human activity. Effective management and restoration of riparian ecosystems is increasingly urgent, for both the conservation of much terrestrial and aquatic biota and the wellbeing and livelihoods of people throughout the world. Management approaches range from protection of intact riparian ecosystems to active revegetation of degraded riparian zones. Significant knowledge gaps exist in many places, however, regarding relationships between riparian ecosystem structure and function and the responses of these to disturbances and management interventions.