Across the globe, rising sea levels are having a profound effect on the natural environment. Although the problem will most directly affect people living in coastal areas it will be also be felt inland and will be especially extreme for populations living on islands. Unfortunately, scientific research shows that the damage has been done. Now we must deal with the urban, social and economic consequences of this accelerating process by adapting existing natural and urban infrastructures. Flooding, severe storms, and shoreline erosion will result in the widespread displacement of populations, as well as damage to coastal cities and ecosystems. An interdisciplinary approach—combined with sharing knowledge and investment in innovative design and planning strategies—will be required to meet this challenge.