Ghost Forests Send a Message

Ancient tree roots render haunting prophecy of shoreline erosion yet to come

By Dan Fagin | Staff Writer

The ghost forest lies at the end of a rutted road through a piney woodland, beyond a stand of cedar and tupelo trees, across a grassy wetland and over a weathered dune to the edge of a gently arcing beach on the southern shore of Flanders Bay.

Coated with barnacles and diminished to their stumpy roots by erosion, the Atlantic white cedars on the beach at Hubbard County Park aren't much to look at. But the trees have been dead for thousands of years, and the story the ghost forest tells is about an island that is one of the most physically dynamic places on the planet.

Long Island is geological history in the making. While much of the world changes only along the multimillion-year time scale of sliding continental plates, Long Island undulates before our eyes, thanks to the tremendous forces of wind, tide and shifting sea level that pound away at an island made mostly of soft sand, not hard rock. Bluffs and beaches can give way at breathtaking speed, while barrier islands roll toward the mainland quickly enough for their movements to be tracked from year to year. And the foot-per-century worldwide rise in sea level is not only shrinking the Island at its edges, but also gradually pushing up the underground water table and flooding formerly dry land far from the coast.

``This is a dynamic place. You can stand on a cliff during a nor'easter and watch it eroding at your feet,'' said Les Sirkin, a research professor of Earth sciences at Adelphi University.

Nature isn't the only force changing Long Island, of course. Humans have had a powerful impact, especially during the last 50 years as the population of Nassau and Suffolk Counties has more than tripled to 2.6 million. Sea walls, jetties and dredging have altered the pattern of erosion. Drinking-water wells and sewer systems have slowed the natural rise in the water table, and development has drained many of the wetlands that would be expanding as the water table rises.

Although human activity has obscured many of the signs of Long Island's dynamism, they are still visible to the trained eye. And they denote the Island's continuing natural evolution as surely as a budding crocus signifies the passage from winter to spring.

Faded stripes on oceanfront cliffs mark oscillations in sea level, and so do the subtle stair-step beaches that lie above and below the water line. Shoreline landmarks like the Montauk Lighthouse and Ocean Parkway serve as fixed reference points to measure the longterm impact of erosion. And far from the coast, expanding swamps and shifting forest boundaries all point to a shrinking island.

Nowhere is Long Island's ever-changing topography more dramatically evident than in the ghost forests.

The term was coined by geologist Steve Englebright, a member of the state Assembly and curator of the Museum of Long Island Natural Sciences in Stony Brook who identified the ancient trees on several East End beaches, including Hubbard County Park, Montauk Point State Park and Mashomack Preserve on Shelter Island.

On a warm morning, Englebright tripped along the shoreline at Hubbard with the enthusiasm of a schoolboy on the first day of summer, waving his arms in sweeping gestures that took in the entire tableau of beach, dune, marsh, grassland and, finally, distant tree line -- all of it undisturbed by humans.

``What you are seeing is the natural evolution of Long Island,'' he said. Toeing a desiccated tree root on the narrow beach while pointing to a line of cedars 100 yards inland, he said, ``What used to live here now lives way back there.''

Englebright explained that the Atlantic white cedar, rare in New York, tends to grow only on the boundary between grassland and forest. So the stubby cedar roots on the shore, he said, must be the remnants of ancient trees that were alive when the sea level was much lower, and when the beach was a few hundred feet farther out.

The twin forces of shoreline erosion and rising sea level not only changed the location of the beach, they set off an ecological chain reaction that pushed everything else back, too: the dune, the swamp, the grassland, and the line of cedars marking the beginning of the pine forest. ``The pine barrens have been pushed back over the centuries, and this is the proof,'' Englebright said.

Tests on the ancient trees support his idea. Radiocarbon tests show that cedar roots on the beach at Montauk are 6,500 years old, and that similar stumps at Mashomack are 4,200 years old. The ghost forest at Hubbard County Park has not been tested, but Englebright believes that the cedar roots at the shoreline here are at least 3,000 years old.

The cedars aren't the only clue to the big changes at Hubbard.

Crouching at the shoreline and digging eight inches into the sand, Englebright pulled up a handful of peat. The dark-colored material consists of decomposed plants, and doesn't occur naturally under bare beaches. Instead, it forms at the bottom of densely vegetated wetlands like the swamp located 20 yards away from the shoreline at Hubbard. The peat under the beach, he said, must have been deposited centuries ago when sea level was lower and the site was a swamp.

Then Englebright walked to the inland edge of the dune and pointed out that it, too, is on the move. A wedge of overwashed sand now extends off the back edge of the dune and into the marshy grass that marks the edge of the swamp.

The swamp isn't standing still, either. Even as it loses ground to the dune on one edge, the freshwater wetland appears to be expanding on its opposite edge into the open grassland that leads to the forest. The swamp's expansion may be yet another consequence of sea level rise, Englebright said. Wetlands across Long Island have gradually expanded over the centuries because the freshwater aquifers beneath the Island float like a bubble on top of a curved bed of salt water. As sea level rises, the salt water compresses the bubble from all sides, forcing up the water table and flooding formerly dry areas.

What it all means is that gradually, the bay is wearing away the dune, the dune is creeping back into the swamp, the swamp is flooding the grassland, the grassland is expanding into the line of cedars, and the cedars are pushing back the pine barrens.

Throughout Long Island, similar chain reactions are underway -- almost all of them set off by sea-level rise and shoreline erosion.