Behind the Dunes

Hidden from view is a salty, windy, sometimes wet environment where specialized species have evolved that can cope with the harsh conditions

Photographs and text by Tony Pratt
From the July 2009 issue

Keep off the dunes and beach grass. That message is on signs we often see at the beach. The reason we are advised to stay off is because the common plant found on the dune is beach grass, which does not do well when walked on. So, most of us keep to the ocean or Delaware Bay side of the dunes to help protect them. But what is on the other side of the frontal dune? Within open, undeveloped beach areas, that other side is a surprisingly natural and diverse habitat. The physical conditions are harsh, yet the variety of plants and animals that inhabit this zone are plentiful.

This ever-evolving, malleable landform is a unique environment that is home to plants and animals that have adjusted to the physical conditions found here. For many of them this is either the only place they call home or it is an essential component in their life cycle.

The back dune environment, by most accounts, is a pretty harsh habitat. The soil is sand and the water source can be either salty or fresh, depending upon the weather. What is interesting about the hydrology of barrier islands is that fresh rain water that percolates through the sand accumulates beneath the surface in a fresh groundwater pool. When enough water accumulates there, or when the sand surface is lowered by the wind, the surface of the groundwater emerges above the ground surface. This wet land supports unique species; for example, there has been a natural cranberry “bog” in a low area in the dunes at Cape Henlopen for years. This is the southernmost documented existence of wild cranberries on the East Coast.

If you were to violate the “keep off the dune” rule and walk over the dune from the beach, you would emerge from the dominant stand of beach grass that is iconic on the ocean side of the dune, shortly beyond the crest of the dune. Dune grass thrives on being buried by sand, so it diminishes farther back from the beach, where other species do better. One of these is a small spring flowering plant called beach heather, which is found in large colonies in many locations on the back side of the dune. It produces a yellow flower in late spring and is often found in such large groups that sometimes the whole dune side is covered in yellow.

Also in the spring, beach plum, a woody shrub of the back dune, explodes into white blossoms. The story has been told for years that the area south of Indian River Inlet is called Cotton Patch Hills because the white blossoms of the beach plums there resembled cotton plants with their bolls ready for picking.

In the low-lying wetter areas of the interior of a barrier island, numerous grasses and sedges take hold. These boggy areas are known as “ephemeral interdunal swales,” which simply means low-lying depressions that may appear and disappear.

Behind the dunes you will also find pine trees and even oaks. Most of the pines you see today are an introduced species that is not native to Delaware. The native back dune pines are pitch, loblolly and Virginia pines, and the native oaks are Southern red, blackjack, post and water oak. Because plants thrive under very specific conditions, the pattern of vegetative cover in the back dune area gives you clues to the physical environment. Where sand blows regularly, beach grass dominates; where it is wet for most of the year, bog plants will win out; where the soil is stable and contains enough organic content, shrubs and trees dominate.

In the back dune area, animal species will take advantage of food or shelter opportunities. The largest animals that inhabit the interior of a barrier island (aside from us humans, of course) are deer. This prolific species seems to survive practically anywhere, and the beach area is no exception.

A much smaller species, the Bethany Firefly, is unique in that it is found only in the back dune area between Fenwick and Dewey. Coastal Delaware once had large colonies of least terns nesting on the open sand of its back dunes. Probably due to an explosion in the number of red foxes that will rob eggs from their nests on the ground, the least terns have moved on to safer sand.

Fox, mice, toads, lizards, salamanders and snakes all inhabit the back dune area. Walking in the dunes one day many years ago, I came upon a hognosed snake that had just bitten into a Fowler’s toad. The snake’s process of working the victim slowly into its mouth was interesting, but more so was what the forensic investigation revealed. The tracks in the smooth surface of the windblown dune sand told the story of a toad hopping its way across the sandy expanse only to be detected by the snake, at quite a distance judging by when the snake turned direction. That is another advantage of the open sandy areas found behind the dunes: Animal tracks are found in abundance, making it easy to see who has passed this way before you.

The land behind the primary dune is interesting indeed, and teeming with plants and animals. So where can you see this environment without disturbing the dune (or breaking the law by going over the front dune)? All dune crossings within the oceanfront state parks offer possibilities to look at the back dune zones. The bicycle trail at Cape Henlopen State Park near Lewes winds south of the bathhouse along the back dune, and includes a spur trail that leads to the beach. South of Dewey Beach, the day-use parking areas at Delaware Seashore State Park have dune crossings, and at Conquest Road, the vehicle access offers nice views behind the dunes.

You have to be patient, but keep your eyes and ears open, stay still and wait several minutes for the birds and other wildlife to calm down from your entrance. Then you never know what you might see.