How a nonprofit uses oysters to prevent shoreline erosion on the Delaware Bay

If you’ve eaten at an oyster bar in Philadelphia or Wilmington recently, it’s likely that you have helped to prevent shoreline erosion along the banks of the Delaware River, especially its bay, which hosts the hard-driving waters of the Atlantic Ocean.

Since 2008, the Partnership for the Delaware Estuary has been installing bags of oyster shells, recycled from restaurants in Philadelphia and Wilmington, on the Delaware’s muddy banks as part of their Living Shorelines program.

The initiative aims to prevent and reverse shoreline erosion through environmentally-friendly means — bags of oyster shells in this case — instead of manmade methods such as bulkheads and seawalls, which can disrupt a shoreline’s natural processes and cause direct habitat loss. Instead, the shell bags form oyster reefs that act as natural seawalls that protect shorelines without causing damage to their delicate ecosystems.

Installing the shells

At this spring’s installation in Collins Beach, Del., white sunshine slipped through passing tufts of clouds hanging high in an early May sky and pours down onto the backs of Leah Morgan, Jessica Klinkam, and Ken Williamson, three PDE staff members who are conducting the installation in shin-deep mud.

While the installation at Collins Beach is one of the smaller Living Shorelines projects, Morgan said the shoreline still benefits.

“This work really helps with shoreline mitigation, especially when we are facing rising sea levels and recurring extreme weather events,” she said. “It helps to retain sediment along the coastlines, which protects shorelines, provides habitat for other critters, and allows baby oysters to recruit [the process of establishing new oysters into the population by attaching to a hard surface, thus allowing them to grow] more easily.”

As time passes and the marshy shoreline grows into the line created by the shell bags, the bags themselves disintegrate, leaving only the oyster reef and its restored shoreline.

Similar to coral reefs in tropic waters, the oyster reefs created from PDE’s installations perpetuate biodiversity and host an incredible ecosystem for other shellfish, invertebrates, and small fish to exist in.

The restored shoreline also positively affects birds and small mammals that find habitat in its marshes.

Collecting the shell

Before the oyster shells can be cured, bagged and installed, they need to be eaten, discarded, and picked up. Williamson makes his rounds in Philadelphia twice a week, picking up trash cans filled with discarded oyster shells from restaurants participating in the recycling program.

Since PDE began the Philadelphia recycling program in 2022, it has collected more than 112,000 pounds of shell.

Following pickup, Williamson deposits the stenchy shells in a lot at the Philadelphia Water Department, one of several shell lot locations. There, the shells will sit for six months to a year to cure — a process where long exposure to sunlight kills the remaining bacteria living on the shell.

After the curing process, the shells will be bagged by PDE staff and volunteers, and eventually installed along the shorelines of the Delaware Bay.

As PDE’s Living Shorelines program continues to grow and more restaurants in Philadelphia and Wilmington join the recycling program, it isn’t just the Delaware Bay’s shorelines that are getting support from recycled oyster shells. Projects like PDE’s Living Shorelines are a worldwide effort, from New York City and South Carolina to the Netherlands and Bangladesh.

These efforts around the globe have proved the success of oyster shells working as natural seawalls, and because of it, they can play a crucial role in dampening the effects of manmade climate change in the Delaware River Watershed and beyond.