Extensive oyster reefs once thrived along much of Europe’s coastline, but recent findings reveal that these intricate ecosystems were lost over a century ago.
According to documents from the 18th and 19th centuries, the European flat oyster created vast reefs comprised of both live and dead shells, offering a habitat rich in biodiversity.
Currently, oysters are mainly found as isolated individuals; however, researchers uncovered signs of reefs scattered across regions from Norway to the Mediterranean, spanning at least 1.7 million hectares—an area greater than Northern Ireland.
The study was undertaken by researchers from the University of Exeter and The University of Edinburgh.
Native oyster reefs fostered diverse ecosystems, supporting a higher number of species compared to their surrounding environments.
Besides providing homes for nearly 200 known species of fish and crustaceans, these oysters significantly contributed to shoreline stabilization, nutrient cycling, and water filtration—one adult oyster can filter up to 200 liters of water daily.
Ongoing restoration initiatives are being conducted across Europe, including small-scale habitat restoration efforts like The Wild Oyster Project, led by ZSL and its partners, which are crucial steps toward the revival of these essential ecosystems on a global scale.
Nevertheless, to restore these habitats effectively, there needs to be increased support from governments and decision-makers throughout the continent.
“Human activities have impacted the ocean for centuries,” remarked Dr. Ruth Thurstan from the University of Exeter, who is involved in the Convex Seascape Survey—a significant five-year project focused on ocean carbon storage.
“This long-standing impact makes it challenging to understand what our marine ecosystems once looked like, complicating efforts for conservation and recovery.
“Nowadays, few people in the UK have seen a flat oyster, our native species. While oysters still inhabit these waters, they are now scattered, and the reefs they once formed have disappeared.
“We often envision our seafloor as being flat and muddy, but historically, many areas featured a three-dimensional landscape of vibrant living reefs—now entirely absent from our collective memory.”
Due to their economic and cultural importance, oysters are documented in historical records such as newspapers, books, travel writings, landing logs, nautical charts, early scientific studies, and fisherman interviews.
“By merging descriptive accounts from diverse historical sources, we can recreate a visual of our oceans in the past,” explained Dr. Thurstan, who is charting historical oceanic changes as part of the Convex Seascape Survey.
“The North Sea showed the highest concentration of oyster reefs according to our findings.”
Records indicate that extensive reefs once existed along the coastlines of what are now France, Denmark, Germany, the Netherlands, the Republic of Ireland, and the UK.
“Oyster reefs grow slowly, as new layers of oysters form atop the shells of their predecessors, yet their destruction due to overfishing was quite swift,” noted Dr. Philine zu Ermgassen, honorary researcher at the University of Edinburgh.
“This rapid decline has fundamentally altered and flattened our seafloors, erasing thriving ecosystems and leaving behind just soft sediment.
“Thanks to this historical ecological research, we can now accurately describe what oyster reefs looked like prior to being disturbed and outline the vast ecosystems they supported.
“These regions were once heavily populated with oysters and teeming with marine life.”
The research team comprised over 30 European scientists from the Native Oyster Restoration Alliance.
This study received partial funding from the European Research Council.
