Last April, researchers in Southern Nigeria published the first-ever scientific assessment of coastal areas underwater due to sea level rise. In the southeastern part of Lagos, Nigeria’s commercial capital, a community of 15,000 people—many of them farmers and fishermen—are in grave danger. On paper, Nigeria is well prepared for the impacts of climate change, says Daniel Horowitz of the United Nations Population Fund, but in fact the country has the worst record on poverty in the developing world. Over the next four decades, his organization estimates that coastal flooding could cost Nigeria $236 billion in agricultural production and public health costs. Addressing the danger from rising seas would mean rebuilding entire communities, cleaning up an area at the coastal edge, relocating the people who live there, and redefining their lives. The nation has made some progress toward implementing climate change-proof strategies in the seaside settlements, but with conditions that make them difficult to implement. Still, the poor are the people most at risk from climate change. I visited four Lagos villages affected by the rising sea.