Not so long ago, many islands rose above the brackish waters of
the Chesapeake Bay. These small islands offered a predator-free haven for
nesting water birds and turtles, while the larger islands supported fishing
communities along with wildlife. But now, the muddy, marshy islands are eroding
under the combined forces of geology and climate change. The very crust under
the Chesapeake Bay is sinking, while sea levels are rising. Made of clay and
silt, the islands erode quickly, and many have disappeared altogether.
Poplar Island ranks among those that would have been gone a
decade ago if not for a massive restoration project. In the 1800s, the island
had an area just over 1,000 acres and held a small town of about 100 people. By
the 1990s, the island was nearly gone, containing a mere 10 acres of land. In
the left image, taken by the Landsat 5 satellite on June 28, 1997, Poplar
Island had been reduced to a tiny green dot surrounded by clouds of silt-laden
water.
In 1998, the U.S. Army Corp of Engineers began to restore Poplar
Island. The project serves two purposes: it restores lost habitat to birds and
turtles, and it provides a use for material dredged from Baltimore Harbor and
Chesapeake Bay shipping lanes. The method of restoration is visible in the
center image, taken on June 21, 2006. Engineers built dikes around sections of
the island and have been gradually filling in the center with dredged silt. By
2006, the island had regained the shape it held in the 1800s.
As each cell is filled with new soil, the Army Corp of Engineers
plants vegetation. The right image, taken on July 5, 2011, shows that much of
the island has been re-vegetated. Poplar Island now has an area of 1,140 acres
and may continue to expand by another 500 acres before the restoration is
completed in 2027. Upon completion, Poplar Island will be half wetlands and
half uplands covered by forest. The restoration project is expected to cost
$667 million, says the U.S. Army Corp of Engineers.
Islands and shorelines in the Mid-Atlantic may become
increasingly vulnerable to erosion. Sea levels are rising as the ocean warms
and expands—and as glaciers and ice sheets melt—but the rise isn't uniform
around the planet. Currents, salinity, and topography create areas where sea
levels are increasing more quickly, and recent researchfound that the U.S. Mid-Atlantic coast
is one of the areas of accelerated sea-level rise. The rate of increase in the
densely populated Mid-Atlantic is three to four times greater than average
global sea-level rise. The increased sea level will make coastal regions and
islands more prone to flooding and erosion.
A short animation of the Poplar Island restoration is
available from the NASA Scientific Visualization Studio.
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