Changes in human populations, water use, climate, and related disturbances are impacting riparian ecosystems throughout the western United States. Nowhere is this more pronounced than in the arid American Southwest (Gutzler 2013; Molles et al. 1998; Webb et al. 2007). Changes in southwestern riparian ecosystems are often visible to the casual eye in the form of reduced and channelized water along stream courses, loss or changes in riparian vegetation, fire, and urbanization. To manage these changes and improve ecosystem resiliency for the future, a better understanding of the impacts of stressors and disturbances on southwestern riparian ecosystems, and especially on resources of high value from human and ecological perspectives, is needed. We focus on aridland riparian forests in this chapter owing to their values for recreation, wildlife habitat, and energy and nutrient input.