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April 4, 2017
A group of students from Horn Point Laboratory Professor Judy O'Neil's biological oceanography class visited Poplar Island, a largely manmade stretch of land a few miles off Tilghman Island in Chesapeake Bay.
This once political retreat boasted 1,100 acres when it was first surveyed in 1847, but by 1993, all but 5 acres disappeared below the waves due largely to erosion and sea level rise.
"Poplar virtually disappeared due to erosion," Megan DiFatta, environmental specialist for Maryland Environmental Service, told the tour group.
The state of Maryland partnered with the Army Corps of Engineers to rebuild the important wildlife habitat, which has been home to more than 200 species of birds and 155 insect species. Every year, the island also welcomes about 1,000 hatchlings of the state reptile, the terrapin. Some of those terrapins spend the school year with local students, who will return them grown up to Poplar Island where they are released into the Bay.
The Paul S. Sarbanes Ecosystem Restoration Project has brought Poplar Island back to 1,100 acres, the result of years of necessary dredging in the Port of Baltimore’s approach channels.
"We compare it to a ice tray. We're filling it in one section at a time," DiFatta said.
O'Neil, an associate research professor from Horn Point who has arranged the Poplar field trip for years, said she likes to show students in the Marine Estuarine Environmental Sciences Graduate Program course a success story in the Bay.
"It was a win-win both for restoration and commerce," O'Neil said. "Because The Port of Baltimore needs to have deeper channels, so they need to be dredged on a very routine baisis, but they need a place to put the sediments and Poplar Island was being eroded."
Listen as Judy O'Neil talks about the win-win project
Material pulled from the channels has given shape back to Poplar Island. The overall project will take 68 million cubic yards of dredged material, and won't be completed until 2044. While it is back to its 1,100-acre size, there are plans calling to grow the island by another 575 acres. As part of the work, crews are adding vegetation, higher elevation points, and a rock perimeter to help the island withstand future erosion.
During construction, a number of researchers from the University of Maryland Center for Environmental Science, including Court Stevenson, Jeff Cornwell, and Lorie Staver, have been surveying the marshes to learn about the island and how marshes develop there.
During the tour, Staver explained that UMCES scientists have been monitoring elevation of the marshes.
"That’s really critical because marshes are right almost at sea level. So as sea level rises—which it has been, but we’re expecting it to increase—the marshes have to keep up their elevation to keep with sea level rise, or they’ll drown."
Water quality and sediment data that the scientists recorded in 2004 in the restored Poplar Island marsh and a natural marsh at Horn Point indicated the restored marsh is functioning like a natural marsh, though there was evidence of significant differences in sediment chemistry.
The scientists also found that while marshes are not typically rich in nutrients, those on Poplar Island are because of the dredged material. That material from the upper Chesapeake Bay is rich in nutrients and is passing that along to the marshes. As a result, the vegetation on Poplar develops more, Staver said.
"Typically marsh vegetation in this part of Chesapeake Bat is about 3 feet. We have vegetation [on Poplar] that’s about 6 feet tall."
That discovery led to another, unexpected one. The excess of nitrogen in the Poplar vegetation is attracting a lot of insects that graze on the plants. The scientists set up tented areas that allowed them to compare areas of marsh affected by insects grazing with areas untouched by the insects.
"Insect grazing on this marsh is much more significant than we thought it was and there’s also probably a connection with the insects acting as a vector for pathogens that effect the plant production as well," Staver said.
The Horn Point Laboratory scientists use what they learn from monitoring to make recommendations as work continues along other parts of the island.
"Because these wetlands are being developed sequentially, we can use monitoring data to feed back into the design process for future wetland cell development," Staver said.
Poplar Island is open for tours by reservation only. Learn more about Poplar Island.