Biologists estimate that New York City's harbour was once home to half the world's oyster population.
For at least 6,000 years, the oyster thrived in the Hudson River estuary, becoming "deeply woven into the life of East Coast cities", said BBC Future. Thanks to over-harvesting and pollution, they are now "long gone".
But over the past decade, one of New York's "most ambitious rewilding initiatives" has planted 150 million larvae, aiming to seed a billion oysters in the city's waterways by 2035. "The goal: restoring the city's coastal habitat, improving water quality and educating the public."
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The pearls of New York City
"For thousands of years, oysters played a special role in the story of New York," said The Guardian.
"Once a staple of the Lenape people's diet, oysters led European visitors later to write home in wonder of their quality, and colonisers turned them into a major industry".
But overconsumption, and an outbreak of cholera in 1849 that spurred the construction of a sewage system, which dumped waste into the water, devastated the oyster populations. Soon after the cholera outbreak, a link was established between eating oysters and typhoid. The Health Department closed all the oyster beds, with New York's last shut in 1927.
But in 1972, the Clean Water Act banned the dumping of waste and sewage into the harbour. Another turning point came in 2021, said BBC Future, when a hurricane devastated New York and the US East Coast.
"The conversation really changed when we experienced the impacts from Hurricane Sandy," said Carrie Roble, an aquatic ecologist and vice president of estuarine education at Hudson River Park. "Our city began to ask, what's next, how do we protect our communities?"
An educational experiment in 2003, in which a few students planted about 30,000 oyster larvae – "less than a teaspoon" – into the harbour, "grew into a city-wide initiative". Now, several institutions, 100 schools and 75 restaurants recycle oyster shells through the Billion Oyster Project. The Hudson River Park, one of the partners, claims to have added 35 million oysters to New York's waters since 2021.
The unsung environmentalists
Oysters absorb pollutants when they filter the water; one adult oyster can filter 50 gallons of water a day, said The New York Times.
Oysters also "enhance biodiversity"; animals like shrimp and snails grow on their shells, which provides food for fish, and they provide a natural defence against coastal erosion. They are "key in the fight against rising seas and flooding", too.
During a storm, wave energy accelerates over the bottom of a river, but reefs create a "wiffle ball effect" which absorbs much of the momentum, said Roble.
Restoring the oyster reefs could help to protect the city from extreme storms, according to a study recently published in the journal Nature.
London mayor Sadiq Khan also visited the project in September, and committed to "explore the role" that oysters might one day play in cleaning up the River Thames. After all, oyster reefs once stretched across kilometres of the Thames estuary too.
The Solent Seascape Project, one of the biggest restoration projects in Europe, recently used $5 million of funding to introduce more than 14,000 oysters into the River Hamble, said SW Londoner.
"If we are successful in the Solent then absolutely, we can do it in places like the Thames," said professor of marine zoology at the University of Portsmouth, Gordon Watson, of the project.
Other oyster restoration projects are already underway in Bangladesh, Australia and Hong Kong.
