Building land with a rising sea

Cost-efficient nature-based solutions can help to sustain coastal societies [Also see Report by Tessler et al.] Coastal lowlands are increasingly exposed to flood risks from sea-level rise and extreme weather events (1). Megacities like Shanghai, London, New York, and Bangkok that lie in vast river deltas are particularly vulnerable. Dramatic flood disasters include the Indian Ocean tsunami in 2004, Hurricane Katrina in New Orleans in 2005, Hurricane Sandy in New York in 2012, and Typhoon Haiyan in the Philippines in 2013. Managing the risks of such disasters requires investments in short-term emergency response and long-term flood protection (2), including nature- or ecosystem-based engineering (3, 4). On page 638 of this issue, Tessler et al. (5) show that sealevel rise, increasing climate extremes, population growth, and human-induced sinking of deltas threaten the sustainability of many major deltas around the world.