Coastal cities have a hidden vulnerability to storm-surge and tidal flooding − entirely caused by humans

Centuries ago, estuaries around the world were teeming with birds and turbulent with schools of fish, their marshlands and endless tracts of channels melting into the gray-blue horizon.

Fast-forward to today, and in estuaries such as New York Harbor, San Francisco Bay and Miami's Biscayne Bay - areas where rivers meet the sea - 80% to 90% of this habitat has been built over.

The result has been the environmental collapse of estuary habitats and the loss of buffer zones that helped protect cities from storm surge and sea-level rise. But the damage isn't just ...