Once a rare occurrence, building collapses in Alexandria—one of the world's oldest cities, often called the "bride of the Mediterranean" for its beauty—have accelerated from approximately one per year to an alarming 40 per year over the past decade, the researchers found.

"The true cost of this loss extends far beyond bricks and mortar. We are witnessing the gradual disappearance of historic coastal cities, with Alexandria sounding the alarm. What once seemed like distant climate risks are now a present reality," said Essam Heggy, a water scientist at the USC Viterbi School of Engineering and the study's corresponding author.

"For centuries, Alexandria's structures stood as marvels of resilient engineering, enduring earthquakes, storm surges, tsunamis and more. But now, rising seas and intensifying storms—fueled by climate change—are undoing in decades what took millennia of human ingenuity to create," said Sara Fouad, a landscape architect at the Technical University of Munich (TUM) and the study's first author.

Coastal erosion: Sinking cities and rising seas

Even small sea level increases—just a few centimeters—can have devastating effects, Heggy said, threatening even cities as historically resilient as Alexandria, which has withstood centuries of earthquakes, invasions and fires, and even a modern metropolis like Los Angeles, where flash floods and mudslides are now complicating recovery from the recent wildfires.