ATAFONA, Brazil— Sônia Ferreira struggles to remember what this deserted fishing community near Rio de Janeiro looked like when she moved here some 50 years ago—mostly because a good chunk of it is now at the bottom of the Atlantic Ocean. The coastline is receding as much as 18 feet a year at the mouth of the Paraíba do Sul river in Atafona, home to 7,000 people, satellite images show. Between 1984 and 2016, some 550 feet have disappeared. Climate change has increased sea levels, scientists say, and most of the river’s water has been diverted to nearby cities, farms and factories, thwarting its ability to push back the ever-higher waves that sweep away buildings, livelihoods and memories.

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