By the 1990s, Poplar Island, a sandy sliver of land in the Chesapeake Bay once boasting more than a thousand acres, was almost completely gone. Today, this island, shaped like an inverted comma, can again be found just off Maryland’s Eastern Shore, a short trip from popular vacation spots where millions of visitors flock to boat on the bay and dine on blue crabs.

Over the past couple of centuries, however, the Chesapeake has made a habit of eating its islands, erosion consuming hundreds of the sandy outcrops along with houses, farms, stores, and churches. That was Poplar Island’s fate, and in the first half of the 20th century, its small community of farmers and watermen fled to firmer ground. More than 20 years of painstaking engineering have resurrected this lost island. Rising seas, though, are waiting patiently to take it back.

Water takes away, but it also provides. The rebirth of Poplar Island has its roots in soil from farms and construction sites in Pennsylvania and surrounding regions that wash silt and debris, which clog up shipping channels, down the Susquehanna River. In 2001, dredgers started scooping up this lost land by the millions of cubic yards to keep valuable commerce moving into the Port of Baltimore.

A coalition of state and federal agencies, led by the Maryland Port Administration and the US Army Corps of engineers, saw an opportunity. Why not use that dredged material to rebuild Poplar Island?

Decades later, the project has attracted international attention from countries like the Netherlands for its beneficial use of dredging material. Engineers work closely with researchers and environmental agencies to craft the dredged soil into more than 1,700 acres of wildlife habitat. It’s the largest project of its kind in the US, Alex Baldowski, a civil engineer with the Corps’ Baltimore District, said.

“It was shocking how fast the birds arrived, migratory birds especially,” said Lorie Staver, an associate research professor at the University of Maryland’s Horn Point Laboratory, who has been involved with the project almost since the beginning. Horn Point is part of the island’s project team.

There’s one hitch: By the end of the century, large portions of this bird paradise could sink back under the waves of the Chesapeake Bay. The project isn’t cheap either. By the time work ends around 2040, the island will have cost more than $1.4 billion, according to projections.

The Army Corps argues this project is still very much worth the investment, and scientists inside and outside the project agree. In fact, the Corps is gearing up to restore thousands more acres on James and Barren Islands farther south in the bay. 

Frank Galgano, an associate professor of geography at Villanova University who has studied coastal erosion, spent time researching Sharps Island, which no longer exists but once lay at the mouth of the Choptank River, a tributary that flows into the Chesapeake from Maryland’s Eastern Shore.

There’s more going on with the bay’s islands than sea level rise, he said. Some of them are alluvial deposits, essentially material washed there by rivers like the Choptank. They’re naturally fragile and eventually wash away as conditions change.  

Galgano doesn’t think it’s a bad idea to reuse dredge materials for islands, depending on costs and how long they can be made to last. “They do have to put the dredge spoils somewhere,” Galgano said. “[A]nd it would seem like a useful plan to supplement what’s left from these islands and create a habitat.”

Birds, terrapins, and seaborne commerce

A sandy road leads around the perimeter of Poplar Island and through construction zones divided into cells. At this stage of development, the windswept island has few trees. In finished cells, tidal channels cut through marsh grass. Newer sites feature broad plains of dark brown silt, cracking as it dries, or saltwater ponds.

Barges unload dredged sludge, which Seth Keller, a Corps biologist, compares to pudding. The sludge is mixed with water to create a slurry more like chocolate milk, which is spread over the cells. The silt settles, the water is released back into the bay, and the cells fill up and dry out. The finished island will feature areas of low marsh, high marsh, and upland habitat with trees.

Much of the island remains a sprawling construction site, with temporary buildings for workers and specialized machinery dotting the landscape. But even so, it’s already teeming with wildlife.

Diamondback terrapins, whose decline concerns conservationists, make their home here, along with endangered common terns and threatened least terns. More than 200 species of birds have been spotted on the island, including glossy ibises and snowy egrets. It even hosts a small herd of deer that either swam over or crossed on ice. Bald eagles recently built their first nest on the island.

It’s an ecological gem, Staver said, an important replacement for the bay’s lost islands. “It’s just been super successful as a habitat restoration.”

Gussie Maguire, Maryland staff scientist for the Chesapeake Bay Foundation, agrees, saying the site has created fantastic bird and fish habitat at a time when sea level rise is quickly turning regional marshes into open water. She says the island is also valuable for its isolation from human development and agriculture. (Her conservation organization offers input on Poplar Island but isn’t directly involved.) “This is a really pivotal spot in the Atlantic Flyway,” a north-south corridor for migratory birds, Keller said.  

The Corps recognizes that much of this habitat may be submerged by the end of the century. However, the argument in favor of the project is essentially this: Dredgers have to keep the Port of Baltimore open for shipping, and that material has to go somewhere. Even without Poplar Island, this expensive work would continue.

The economic payoff is dramatic. The Port of Baltimore is estimated to generate a little over 20,000 direct jobs, along with about $5.3 billion in personal wages and $647 million in state and local tax revenues each year, Holly Miller, director of navigation and stewardship at the Maryland Port Administration, said. The cost of the habitat portion of the project is miniscule compared with the costs associated with dredging, Keller added.

There are several reasons to avoid dumping the dredged material out at sea. Baldowski noted that this can cause multiple catastrophes. The sediment covers the seafloor, suffocating living things, and the nutrient-rich dredged soil can cause algae blooms that kill fish and other creatures. Also, dredging costs add up quickly with distance, so transporting it to the ocean would not be cheap.

It’s not much of an option anyway. Around the time of Poplar Island’s founding, Maryland legislators banned dumping dredging material in its waters and prioritized beneficial reuse of dredging materials as the first option, Miller said. That makes projects like Poplar Island, with their capacity for tens of millions of cubic yards of dredged material, a crucial part of the state’s plans.

The new Poplar Island should also be more resilient than the old version. The shores of Poplar 2.0 are armored with granite. The original was mostly made up of sand and soil, as boulders are pretty much nonexistent in this part of the world. This fragile structure was held in place by tree roots, Baldowski said, but settlers axed the trees.

Staver also argues that the islands are worth the investment, even if they aren’t permanent. All island habitat comes and goes in the geological long haul, she said, and species have adapted to take advantage of it while it’s there. And while Poplar Island’s marshes may disappear, the uplands could last centuries, she maintains.

Unlike many engineering projects, the work on Poplar Island is spread out over decades, Baldowski notes, and designers glean insights from this gigantic sandbox experiment. They constantly update their approach based on new conditions. 

This includes ongoing revision of marsh designs, Staver says, working to make them more sustainable, resilient to sea level rise, and more suitable to the organisms moving in. “If (the marshes) last for 40 years, that’s great, but maybe they’ll last longer.”

If the Corps decides it’s worth it down the road, they can use a technique called thin layer placement, spraying sediment-laden liquid to gradually build up the marshes.

“There’s sort of a never-ending supply of dredge material that they could be placing and raising up the cells to keep pace with sea level rise,” Maguire said. “I think it’s a solid partnership, and I think they’ve done really great work.”