Researchers have revealed that Europe’s native oyster reefs – the continent’s equivalent of tropical coral reefs – have been so damaged by human impacts that they are now considered ‘collapsed’, according to the IUCN’s Red List of Ecosystems criteria.
The European native oyster (Ostrea edulis) – also called the European flat oyster – is the only true oyster species native to UK waters. The new assessment, led by ZSL (Zoological Society of London) and the University of Edinburgh, has revealed that these oyster reefs were once vast habitats that could grow as large as a football pitch; they were bustling habitats for many species, covering more than 1.7 million hectares of European waters – that’s larger than Greater London.
Today, as a result of overfishing, pollution, and other human impacts, there is almost nothing left of these once-thriving ecosystems. The paper, which has been published in the journal Conservation Letters, found most oyster reefs in Europe are scattered and degraded, with oysters found alone or in small clusters.
“The ecosystem has been lost from living memory, and the benefits it provided have only just been realised now it is almost too late,” says Alison Debney, ZSL Conservation Lead, Wetland Ecosystem Restoration and co-founder of the Native Oyster Network UK & Ireland.
Oyster reefs play an important role in keeping the ocean healthy. As the oysters settle, one on top of another, they create nooks and crannies for other animals to call home. Over time, the reef becomes a thriving ecosystem full of fish, crabs, shrimp and other critters. Even birds, like oystercatchers, benefit from feeding on the oysters.
With the loss of these oysters, all these animals are impacted too. “Possibly even more stark [than the collapse of the oysters] is the loss of biodiversity that preyed or lived on these reefs and the organisms that inhabited them,” says Joanne Preston, Professor of Marine Biology, University of Portsmouth and co-founder of the Native Oyster Network UK & Ireland.
Oysters are filter-feeders that sieve tiny particles from the water to eat, which keeps the water clean – one adult oyster can filter up to 200 litres of water each day. They also provide food and livelihoods for local communities and protect the coastline from strong waves and storm impacts.
The researchers hope this shocking news will prompt decision-makers to think about what else can be done to bring our oceans back to their previous state. “The stark contrast between the modern-day flat seabed and historical data must act as a wake-up call for action to restore the once-thriving marine environments,” says Debney.
“We were shocked by our findings,” says Dr Philine zu Ermgassen of the University of Edinburgh who believes current restoration efforts alone aren’t enough to bring native oyster reefs back to their original level of health. “True ecosystem recovery requires systemic processes and sustainable financing.”
Although restoration projects aren’t a quick fix, because oyster reefs take a long time to regenerate, Debney has hope as long as European decision-makers take significant steps to restore oyster beds. “Given time and space, nature can recover,” she says.
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