The estuary formed by the flowing Hudson River creates a brackish paradise for a richly biodiverse and elaborate ecosystem. According to the New York State Department of Environmental Conservation, long before the river was named for Henry Hudson, “Native tribes called it ‘Mahicantuck,’ which means ‘great waters in constant motion’ or more loosely ‘river that flows two ways.’” Native Americans discovered the [river’s] bounty thousands of years ago; evidence of their repasts remains in heaps of oyster shells on its shores.”

As Europeans flooded onto the island of Manhattan, known then as Little Amsterdam, the natural resource quickly became an industry easily harvested and (what seemed to be) endlessly replenished. Mark Kurlansky, author of “The Big Oyster,” writes, “before the 20th century, when people thought of New York, they thought of oysters.” The island had earned an international reputation for its straight-from-the-harbor oysters and even gained the title of Oyster Capital of the World, attracting tourists who wanted a taste of everything the city offered.

With this lifestyle and reputation to maintain, it only took 100 years to deplete the harbor’s oyster population. Unregulated toxic dumping combined with over-harvesting the water’s natural filter rendered the New York Harbor nearly lifeless by 1906.

While regulations came into play and helped the flowing Hudson do its job in flushing out the water, it wasn’t until 1972 that the Clean Water Act was put into place, and not until 2000 that the water quality in New York Harbor improved enough to support oyster life – however, the water today is still not clean enough to consume those oysters. Improvements continued, and in 2010, for the first time in a century, whales were spotted in New York Harbor. “It’s encouraging that there’s something to see now,” says Madeline. “Our students and volunteers have found Fiddler Crabs, Blackfish (which eat mussels, barnacles, crabs, and oysters), American Eels, horseshoe crabs, and even seahorses.” By focusing on oyster reefs, the ecosystem gets support from the bottom up – which is why oysters are fondly referred to as “ecosystem engineers.”

So how does putting shells back into the water equate to more oysters? Oyster larvae are free-swimming and spend their first days to weeks in search of a hard, suitable substrate to settle on, one rich with calcium carbonate, so each larvae can grow a shell of its own. Beautifully enough, existing oyster (and other shellfish) shells provide that ideal substrate. Billion Oyster Project’s Hatchery Manager cultivates oyster larvae in tanks at the Harbor School Hatchery and sees to it that they have set to shell. This phase is known as "spat on shell.” From this point on, the oyster will not move and is ready to enter New York Harbor at a Billion Oyster Project reef site.

The other part of the equation is creating a nice foundation in the harbor, which is where existing oyster shells come in. After an oyster installation, the work then becomes about monitoring the reef sites – which is where school groups and volunteers get involved, becoming community work.

Billion Oyster Project isn’t just a name, it’s a numeric goal they’ve set to reestablish one billion oysters to the New York Harbor by 2035. Madeline shares that “A lot of people feel guilty and think, ‘Should I be eating oysters?’ But oysters are actually one of the more sustainable seafoods. We don’t discourage it, but we do encourage choosing restaurants that recycle their shells and choose sustainable sources. Our work wouldn’t be possible without the discarded shells.”

Earlier this year, Billion Oyster Project put in about 500,000 pounds (which amounts to 600 cubic yards) of oyster shells – from the first two years of collection (which began in 2015). But since New York Harbor’s oysters are not safe to consume, the shells collected from the city’s restaurants are not local and, therefore, can’t be immediately returned to the water. Instead, the shells must sit out exposed to sun and rain, so any pathogen or tissue is dead or removed before they are introduced into the local ecosystem. It is generally one full year before Billion Oyster Project shells can be introduced into the water from the time the oyster leaves the plate at a restaurant.

It’s a slow process bringing an ecosystem back from the edge of lifelessness and can be a tough sell when the end goal isn’t a harbor-to-happy hour oyster experience. “It’s a nice idea, and it’s possible we could get there in the distant future,” says Madeline, “but that’s not the goal.” Instead, the focus is on two things you can’t order from a menu: a healthy ecosystem and an invested community.