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Regulating ecosystem services (ES) fundamentally underpin biosphere integrity, human safety, and the provision of most other ES. However, the pathways by which regulating ES generate benefits for people are complex and vary spatially and temporally. Emerging ES decision-making frameworks underemphasize regulating services because they focus on ES that have more obvious links to human wellbeing (e.g., in close proximity to beneficiaries with very short time lags). Lack of attention towards regulating ES can lead to unintended management trade-offs that create risk for human wellbeing and can cause immediate and delayed impacts on cultural and provisioning ES. Therefore, a remaining challenge for ES frameworks is to address the full ensemble of processes and feedbacks whereby ecosystems contribute to human wellbeing over time, including through regulating services. We address this challenge by (i) reviewing the complexities associated with regulating ES components—capacity, ecological pressures, and demand, (ii) exploring the spatial and temporal variability that influence regulating ES components, including the flow of service benefits, and (iii) illustrating the interdependency of regulating ES components through examples of ES that are linked hydrologically. We conclude that ES capacity, pressure, demand and the flow of benefits are distinct, but intricately linked components that influence how regulating ES provide benefits and improve human wellbeing. We pose that ES assessment frameworks could be improved by including indicators of regulating ES that differentiate between the capacity to provide a regulating ES, the demand for the same, and the actual service that is conveyed, the latter of which is influenced by underlying capacity and ecological pressure. These indicators should also be spatially and temporally explicit to fully incorporate the dynamic influence of temporal variability, spatial scale, and landscape configuration on regulating ES and the benefits they yield.

Large hydropower schemes have recently gained renewed interest as a provider of efficient and renewable energy, particularly in developing countries. However, some dams may have widespread effects on hydrological and ecosystem integrity, which reach beyond the scales addressed by typical environmental impact assessments. In this paper we address two main ecological impacts—reduced river connectivity and changes in the natural flow regime—at the scale of the entire Mekong River Basin as an important component of dam evaluations. The goal is to improve our understanding of the effect of individual dams as well as clusters of dams at a very large scale. We introduce two new indices, the River Connectivity Index (RCI) as a tool to measure network connectivity, and the River Regulation Index (RRI) as a measure of flow alteration, and calculate the individual and cumulative impact of 81 proposed dams using HydroROUT, a graph-theory based river routing model. Furthermore, we demonstrate how quantitative weighting, e.g. based on river habitat characterizations or species distribution models, may be included in dam impact assessments. A global comparison of large rivers shows that the Mekong would experience strong deterioration in the fragmentation and flow regulation indices if all dams that are currently under consideration in the basin were built, placing it among other heavily impounded rivers in the world. The results illustrate the importance of considering the location of dams, both relative in the network and relative to other already existing dams. Our approach may be used as an index-based ranking system for individual dams, or to compare basin-wide development scenarios, with the goal of providing guidance for decision makers wishing to select locations for future dams with less environmental impacts and to identify and develop potential mitigation strategies.