European coastlines were once lined with oyster reefs, stretching from Norway to the Mediterranean, according to a new scientific study published on Thursday. The study, written by 30 European researchers from various scientific institutes, said the reefs would have covered at least 1.7 million hectares. It said the oyster reefs were destroyed over 100 years ago, mainly from overfishing, leading to a flattening of the seabed. One of the study’s authors, Ruth Thurstan, said that in the past many parts of the seabed “were a three-dimensional landscape with complex living reefs – now completely g…