Coastal areas face special challenges resulting from global change. These challenges are related to three distinct features of coastal areas: concentration of environmental impacts, multiple thresholds, and high sensitivity to climate change. River networks and hydrological processes integrate the consequences of land use and human activities that take place over large areas and, as a result, concentrate their impacts in coastal areas. Coastal areas are characterized by numerous sensitive boundaries and thresholds, i.e., the land-water interface, the intersection of saline and freshwater environments, and constrained space for particular land use patterns. Hence, they are especially sensitive to climate change impacts: a small change in sea level has the potential to push the system beyond a critical threshold and induce radical change in the social-ecological system. Further, the stakes for decisionmaking are high: a relatively large proportion of the population lives in coastal areas, real estate is very valuable, they are often biodiversity hot spots, and are home to very productive agro-ecosystems. This creates a high potential for conflict across multiple user groups. Many policymakers are aware of this situation and generate adaptation plans at their jurisdictional levels. However, policymakers acting in their own jurisdiction may generate spillovers that modify evolution pathways of related social-ecological systems or constrain adaptive capacity of other policymakers operating in other jurisdictions. As a consequence, there are several warning signs of John M. Anderies