A vision of floating cities
By the end of this century, sea levels could rise worldwide by three feet or more, inundating coastal cities and spurring catastrophic storms roughly every three years. In Africa, at least 20 cities — including Cairo, Egypt; Cape Town, South Africa; and Kinshasa, Democratic Republic of the Congo — are especially vulnerable to rising seas. At the top of the list is Lagos, Nigeria, a fast-growing, low-lying coastal city of 13 million. By the year 2100, sea levels there are expected to have risen nearly 4 feet. Houses and roads in Lagos are built on sponge-like terrain that was once sandbars, lagoons, and mangrove swamps. Lagos is also riven with a confluence of inland rivers, adding to its vulnerability to flooding. In 2011, intense rainfall flooded homes, overwhelmed sewers, and turned streets into rivers. Hardest hit in such events are the poor. Slums already hold 70 percent of people in Lagos, a...