Oysters once crowded Europe’s coast – here’s how we discovered these long-forgotten reefs

An artist’s depiction of a dense European oyster reef, based on historical descriptions. Maria Eggertsen/Conservation Letters

Six generations ago, Europe’s seas possessed vast oyster reefs. Oysters were found in their millions, clustered together in reef systems that spanned hundreds of square kilometres. Now the reefs are gone and with them, our collective understanding of what the sea used to look like.

Throughout the 1800s and probably earlier, each August would bring Oyster Day: when...