I’ve turned oysters from a delicacy into a barrier to stop rising seas
Artificial oyster reefs are being created as living breakwaters to limit the damage to vulnerable coastal regions from climate change
Diners slurping oysters in the haute cuisine hangouts of Amsterdam may be unaware, but colonies of their beloved bivalves clumping on reefs a few miles down the coast may be the key to protecting the Netherlands from rising sea levels.
Artificial oyster reefs have been created by Dutch researchers as living breakwaters in an effort to limit the damage to vulnerable coastal regions by calming waves before they reach the shore.
The ability of the molluscs to adapt to their marine environment is seen as a vital tool in tackling a changing climate.
The extraordinary purification capabilities of oysters – a single adult can filter 180 litres of water a day – is also helping revitalise the ecosystem in the salt waters of Oosterschelde in the island-dense province of Zeeland by reducing water pollution from fertilisers and other nitrates so that other species may thrive.
Jim van Belzen, a coastal and estuarine ecologist at Wageningen Marine Research and the Royal Netherlands Institute for Sea Research, is one of a small team of experts engaged in developing this “green infrastructure” alongside stationary measures like storm surge barriers and seawalls to ensure maximum protection for coastal and marine life.
“If we’re able to rely more and more on natural processes that are working by themselves, such as an oyster reef that is developing on its own, then I think we can end up with a much more robust coastal protection system than we have now,” Dr Van Belzen told i.
“And it brings other benefits too,” he added. “There is also a huge need for biodiversity restoration. So these oysters are not only wave breakers, at the same time they are also breeding grounds for all kinds of marine species. So in that respect, they have an added value over just being a part of coastal protection.”
The North Sea, in common with many other parts of the world, once boasted huge populations of oysters in beds and reefs but overexploitation, disease and pollution have driven a 95 per cent decline in numbers since the 1800s. In the last century alone, four fifths of the world’s oyster reefs have disappeared.
Reefs are formed when oyster larvae attach to and grow on other oysters’ shells. The young oysters are known as spat and the resulting structures, comprising living and dead oysters, can grow to hundreds of metres. The first big reef built in Oosterschelde, in 2010, grew to 50 metres long by 10 metres wide.
In their early trials in ecological engineering, Wageningen researchers used the European flat oyster, or Ostrea edulis, a native species that was once very common in the North Sea. Later self-sustaining reefs that proved effective at erosion control were dominated by Pacific or Japanese oysters, or Crassostrea gigas.
“Ideally you want to build an oyster reef and then, hopefully, nature takes over and the reef starts developing on its own,” said Dr Van Belzen.
“In the beginning it didn’t work that well. Some of the reefs were placed too high or too low. And the natural recruitment of oysters was not really taking shape. But thanks to these pilots, we learned better approaches and so the later oyster reefs are doing much better than the first ones we tried.”
The Dutch experts have used the lessons from their trials in the Oosterschelde to grow oyster reefs in Kutubdia Island, one of the most vulnerable spots on the flood-prone south-east coast of Bangladesh. It was the first time the idea had been tested in a sub-tropical, monsoon climate.
As sea levels rise and storms become more extreme, protecting coastlines from erosion and flooding becomes ever more important – especially in Bangladesh, where an estimated sixth of the country’s land could be submerged by 2050, displacing 20 million people.
At Kutubdia, the reefs not only break up the waves but also trap sediment between it and the shoreline. This can enable the planting of mangroves, which further help to protect shorelines from wave damage. The researchers found that the artificial reefs reduced erosion by over half compared to control sites, and were effective in dissipating energy from waves.
Now oyster reef projects are under way all around the world – from the Solent in the UK to New South Wales in Australia. In the US, a Billion Oyster Project is hoping to engage a million people in the effort to restore one billion oysters to New York Harbor by 2035.
The important work being done in Oosterschelde has been noted by the US State Department’s Bureau of Oceans International Environmental and Scientific Affairs, which praised the researchers and said their groundbreaking advances in eco-engineering will be “invaluable” in the international effort to tackle climate change.
For Danielle Brigida, of the World Wildlife Fund, oysters are “the quiet climate heroes, working in places we don’t see, making a difference for our planet” as coastal protection guardians. “By safeguarding coastal areas, oyster reefs help protect human communities and vital coastal ecosystems from the devastating impacts of climate-related events,” she said.
Dr Van Belzen, whose current work involves calculating the optimal locations to site new oyster reefs, is optimistic that there is a greater public appetite to tackle climate change, including support for green solutions such as artificial oyster reefs, than is generally reflected in discussions about the crisis.
“If you ask people, there are so many that want a sustainable life and environment,” said Dr Van Belzen. “A lot of people want to do something about climate change but somehow there is also a general impression that other people don’t want to change. There’s a mismatch there but if we can challenge that idea, maybe the change we urgently need can go much faster than we think.”
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