Barrier-island Migration Drives Large-scale Marsh Loss

2017-01-26T10:14:28+00:00 January 26, 2017|
New study finds loss of barrier islands leads to loss of adjacent saltmarshes. (Credit: Trish Hartmann / Wikimedia)

(Click to enlarge) New study finds loss of barrier islands leads to loss of adjacent saltmarshes. (Credit: Trish Hartmann / Wikimedia)

If you’ve visited North Carolina’s Outer Banks or other barrier islands, you’ve likely experienced their split personalities — places where high waves can pound the sandy ocean shore while herons stalk placid saltmarsh waters just a short distance landward.

(From Science Daily)– New research by a team from William & Mary and its Virginia Institute of Marine Science shows that these seemingly disparate ecosystems are in fact closely coupled, and that rapid landward migration of barrier-island sands is leading to large-scale loss of adjacent saltmarshes. Their study — recently published online in Geology — focuses on the pristine barrier islands of Virginia’s Eastern shore, but is likely applicable to similar barrier-island systems worldwide.

The team’s research shows Virginia’s barrier islands are eroding or migrating landward at 3 to 18 feet per year. They estimate the landward migration consumes at least 60 acres of back-barrier saltmarsh annually, and has buried almost 8,000 acres of these saltmarshes since 1870 — nearly 10% of Virginia’s historical acreage of back-barrier saltmarsh habitat. Loss of marshes is of significant environmental concern given their beneficial role as feeding grounds for waterfowl, nursery grounds for numerous marine species, and ability to absorb carbon, pollutants, and wave energy.

Lead author Charlie Deaton, who conducted the research while an undergraduate in W&M’s Department of Geology, says the team arrived at their results, “by digitizing and analyzing hundreds of maps and photographs extending back to 1851, and comparing these with LIDAR data showing recent shoreline positions.”

Study co-author Dr. Chris Hein, an assistant professor at VIMS, attributes the islands’ changing shorelines to the action of coastal storms. “Hurricanes and nor’easters cause both beach erosion and barrier migration,” says Hein. “Sea-level rise and other factors play a contributing role by setting the conditions for storm surge to erode the shoreline and carry barrier-island sands landward into the marsh.”

The study’s third co-author, VIMS assistant professor Dr. Matt Kirwan, notes that, “Virginia’s barrier islands are exposed to some of the highest rates of relative sea-level rise along the U.S. Atlantic Coast.” A 2015 VIMS study puts the rise rate at Kiptopeke on Virginia’s Eastern Shore at ~3.7 millimeters per year over the last 50 years. That’s a tenth of an inch annually, or more than half a foot of sea-level rise since the mid-1960s.

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