Research on vanishing coastlines in Egypt has lessons for coastal cities in California

Rising seas are threatening Alexandria, one of the world’s oldest cities. A new study by researchers at the University of Southern California (USC) reveals that building collapses there have surged from one per year to 40 annually due to seawater intrusion and coastal erosion. Alexandria’s plight serves as a warning for other coastal cities, including those in California.

Published in Earth’s Future, the study links minor sea level increases to accelerated damage. Satellite data and historical maps show that parts of Alexandria’s coastline have receded by tens of meters in recent decades, raising groundwater levels and weakening building foundations. The problem is compounded by California’s own sinking land, increasing flood risks and saltwater intrusion.

The researchers propose a nature-based solution: sand dunes and vegetation barriers to prevent seawater encroachment. As climate change reshapes coastlines, safeguarding historic cities like Alexandria is about more than preserving architecture—it is about protecting human heritage itself.