NEW YORK (June 16, 2016) –Jamaica Bay’s wetland islands may be just 200 to 230 years old – much younger than was once thought – according to a WCS study that is providing a rare historical glimpse into the bay’s past.   The study appears in online edition of the journal Northeastern Naturalist.

The marsh island wetlands of Jamaica Bay – one of the largest extents of tidal wetlands in New York City – have been progressively disappearing during the twentieth century.  Scientists are unclear about the exact mechanism of loss, but it may be due to some combination of sea level rise, water pollution, wave action, or altered sediment dynamics.  Recent restoration efforts have been focused on rebuilding the marsh islands by adding sediment and planting marsh grasses. 

By reviewing historical maps of the New York City region, some as old as 1501, WCS Senior Conservation Ecologist Eric Sanderson investigated the changing shape of the bay on maps from Dutch, English, French and American sources.

“Jamaica Bay marsh islands are of undoubted importance to the ecology of the city today, because we have lost so much already, said Sanderson.  “But it is unlikely they have always been there.  Looking into the past helps us see how nature shapes New York City and understand the enormous and often expensive efforts required to hold back natural forces.”

Sanderson documents how the Rockaway Peninsula, now home to thousands of year-round residents, did not exist.  The peninsula formed as part of the barrier island system on the south shore of Long Island, growing in fits and starts over the last 400 years, as the result of wave and storm action.  In the historical map series, the peninsula can be clearly seeing elongating and changing shape over time, forming islands and new inlets.

Sanderson hypothesizes that the Rockaway Peninsula created a protective environment that allowed salt marsh islands to form within Jamaica Bay, in the late eighteenth – early nineteenth century.  Changes in the Rockaways were caused by sand moved by a combination of tides, currents, wind, and storms.  These dynamics are common to barrier island systems around the world.

Today, the natural dynamics that governed the southern side of New York City are affected by manmade structures and interventions. Coastal protection measures in the 1920s and subsequently halted the natural evolution of Jamaica Bay and the Rockaways, reinforced by landfill, dredging and bulkheading, fixed Jamaica Bay into its current form.

During the late nineteenth and early twentieth century, some people began to live on the marshes, creating the community of Broad Channel, Queens, and a former community on Ruffle Bar.  After World War II, the Rockaway Peninsula was extensively developed, including housing projects, which were extensively damaged during Hurricane Sandy.

Meanwhile the Army Corps of Engineers is considering a storm surge barrier across the Rockaway Inlet, between the sands of the Rockaways and the former Barren Island (now surrounded by landfill as part of Floyd Bennett Field), as a means of diminishing the threat of flooding from coastal storm surge in the future.

National Oceanic and Atmospheric Administration's Coastal and Ocean Climate Applications program provided funding for this research.  This work was done as part of grant with the Stevens Institute of Technology and Columbia University.