Retired Ecology Professor: Barrier Islands Need Stable Sea Level

CAPE MAY – Ralph Boerner, a retired professor of ecology from Ohio State University, gave the latest lecture in the free “Harborside Chats” series at the Nature Center of Cape May, March 23. 
Boerner now lives in the Cape May Beach section of Lower Township and bills himself as a freelance ecologist and lecturer. He is a native New Yorker who spent many years on the Great South Bay between Long Island and Fire Island, New York.
Boerner said barrier islands require a stable sea level, and over the last 7,000 years, the sea level here has changed about one millimeter. Barrier islands also require a shallow slope to the sea bottom and not a lot of tidal amplitude, which is the difference in elevation between high and low tides.
Boerner contrasted the New Jersey coastline with the California coastline, where there are no barrier islands and no shallow slope to the sea bottom.
“When you enter the water off California, it gets deep immediately,” he said.
Another thing necessary for barrier islands is a good source of sand. For the New Jersey coastline, it is the longshore current that drops sand along the coast on the seaward side of jetties and erodes sand on the opposite side.
Boerner showed a slide of Cape May’s jetties, or groins, with sand buildup on the eastern side and visible erosion on the western side of each jetty. Boerner described how sand carried by waves is blown onto the beaches where it is stabilized by beach grasses that are suited for that purpose. As more sand is deposited, dunes are formed, and if left unchecked, a series of dunes and swales will form.
However, the dunes don’t proceed unchecked mainly because of winter storms. Boerner said summer waves tend to be low energy and dump sand, but in the winter, the waves are more intense and can even be part of storm systems. Storms can also create blowouts in the dune line and allow saltwater to get past the dunes, killing plant life.
Boerner also mentioned that shore towns have used jetties or groins to interrupt the natural slow of the longshore current, which he said helps those “up-current” and harms those “down-current.”
An example of this effect can be found in Cape May, where sand builds on the upward or eastern side of the jetties and is eroded on the opposite side. Another example is Cape May Inlet, where sand has built up on the northern side of the inlet, i.e., the Wildwoods, and eroded on the south side.
Boerner did not limit his talk to the shifting sands of the barrier islands, but also spoke about the ecology, including plant and animal life and Native American life at the shore.
Boerner said the first Native Americans visiting, not living on, the barrier islands lived most of the year on the inner coastal plain, which would have included more of Cumberland and Salem counties. He said they would make seasonal trips to the shore but had no permanent settlements.
“They would use the barrier islands but didn’t live here,” Boerner said.
Boerner said there has been evidence left behind in the form of shell piles left by Native Americans. He suspects there is one currently in Avalon. It is a hill that has two species of plants that thrive in limestone.
Boerner said much of the grass on dunes is American beach grass or marram grass, which tolerate sand, winds, drought, and fire, yet they do not tolerate being trampled. The grass needs about 10 millimeters of sand added each year in order for it to grow. Other dune plant life includes beach plums, bayberry, and the salt spray rose.
Boerner talked about nonnative species of plants as opposed to “invasive” species. He said the term invasive refers to any nonnative species that grows over and kills native vegetation. He said the jury is still out as to whether phragmites, also known as the common reed, are a native plant.
Boerner gave his 50-year outlook for the barrier islands. He said he does not believe, as some do, that the barrier islands will be open water by that time. He said predictions vary as to how much the sea level will rise, but he does believe New Jersey is sinking due to a principle called “isostatic rebound.”
He said the weight of ancient glaciers pushed New Jersey up, like a child on a seesaw, and it is slowly sinking. He said the same effect is noticeable in England.
At the same time, he showed four models that suggest the sea level is rising rapidly. He said some predictions say everything east of the Garden State Parkway will be underwater by 2070 or 2075. 
Contact the author, Christopher South, at csouth@cmcherald.com or 609-886-8600, ext. 128.