When Hurricane Sandy hit New York in 2011, it caused a 14-foot storm surge. And earlier this month New Yorkers were reminded again how vulnerable their coastal city is to flooding. With climate change comes rising seas and more significant storms. It will become more challenging to keep the floodwaters out.
Now, places as diverse as Bangladesh, New York, and the Gulf Coast are turning to eco-engineering, which involves designing ecosystems for the benefit of humans and nature.
Their floodwater solution: building huge oyster reefs to act as a natural breakwater.
How oysters can stop waves: For baby oysters to grow, they first need to stick to something solid. Typically, the baby oysters, called spat, stick to an older oyster or a discarded shell. That is why oysters grow in clumps, with dozens of shells growing on top of each other.
While a concrete reef can be equally effective as a buffer, oysters have added benefits: they filter toxins out of the water, foster a healthy ecosystem, and grow taller over time.
Those clumps of shells are rock solid, and, if they get large enough and numerous enough, they can act as a breakwater, deflecting wave energy away from the shore, reports Vox. The buffer can slow erosion and reduce hurricane damage.
While a concrete reef can be equally effective as a buffer, oysters have added benefits: they filter toxins out of the water, foster a healthy ecosystem, and grow taller over time. This growth can keep up with sea-level rise and reduce maintenance requirements in the long-term.
The oyster effect: Over the last century, 85% of the world’s oyster reefs have disappeared. But several groups around the world are working to rebuild them.
New York’s Billion Oyster Project aims to restore oyster reefs to New York Harbor by collecting used shells via their partner restaurants, bundling them in cages, and sinking them in the harbor for new spat to grow on. Doing so will restore habitats to fish and seagrass, and hopefully help protect the city from storm damage. The project has already collected 1.7 million pounds of shells and restored 47 million live oysters.
In Louisiana, the Coalition to Restore Coastal Louisiana (CRCL) and The Nature Conservancy built a massive breakwater out of 1.7 million pounds of discarded oyster shells collected from 26 local restaurants, reports the BBC. The project, finished in 2016, proved to be successful, as it reduced the rate of coastal wetland erosion by half, a study by CRCL found.
And there are still more oyster-turned-breakwater efforts. The Chesapeake Bay Foundation converts 70 cubic meters of discarded shells into oyster colonies each year in Maryland. And since 2009, Texas A&M University’s Harte Research Institute has gathered over 800,000 kilos of shells and rebuilt approximately 100,000 square meters of oyster reef, reports VOA News.
A double whammy: Perhaps the most significant success is in Bangladesh, where Mohammed Shah Nawaz Chowdhury proposed introducing a new oyster reef to save Kutubdia Island from sea level rise. Already many residents have had to move from their homes as the sea encroaches on the villages. Intense storms and cyclones routinely threaten the coast. But Chowdhury was determined. He spent six years researching the area and building the reef.
“I proposed a partnership with the fishermen. If you take care of the reef, it will take care of you.”
Shah Nawaz Chowdhury
“Potentially, it has been estimated that by 2050, one in every seven Bangladeshis will be displaced by climate change,” Chowdhury told the BBC. “We’re getting more ferocious waves due to global warming and heating waters.”
Oysters are the best substrate to use to start building a reef, but the area didn’t have many. But concrete rings used by the locals to build latrines were readily available, so Chowdhury used the rings as the foundation of the reef. He asked the local indigenous community to help him select the best site, placing the first rings in 2014.
“I always respect indigenous knowledge,” says Chowdhury.
Since the first oyster was seeded seven years ago, the concrete rings have become an active oyster reef. The results of the work were twofold. The new reef provided a breakwater against rising sea levels and storm surges, and by providing a place for fish to spawn, it fostered a rich ecosystem for a local fishery.
“We started finding mud crabs in the rings, drawn by the reef,” says Chowdhury. “Mud crabs have immense export value. 1kg can be sold for $10 [£7.30]. Two to three families can easily make a livelihood off a small oyster reef by adding traps.”
Osman Ali, 55 has spent his entire life on the island. As a fisherman, the work was hard. But he finally had some respite once the oyster reef was established.
“We find a higher abundance of fish, shrimp and crabs near the kostura,” he told BBC. “If a larger reef had been created, it would increase our likelihood of getting more fish.”
“I proposed a partnership with the fishermen,” said Chowdhury. “If you take care of the reef, it will take care of you.”
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