THE DUNES:

Fragile by their very nature, dunes are formed when windblown sand accumulates around an obstruction. This may be insubstantial, and dunes when first formed are quite unstable, prone to”blowout” by strong winds or subject to”washover” from storm waves and wind.

The primary sand dune can vary between poorly developed to well developed on Nannygoat Beach. It is an instant barometer of recent events. After storm waves, its eroded face will show layering of a variety of sand types, sometimes accented by wind erosion. Bioturbation or disturbance by biological agents now shows as disruptions of these layers by the growth of plant roots or by animal burrows. By contrast, accretion occurs after a period of calm weather with onshore winds, and the sand may be seen to be building up and partially burying obstructions like live plants and debris stranded beyond the high tide mark.

At the southern end of Nannygoat Beach, the lines of dunes swing around the corner in great arcs. An aerial view of this area is one of the more spectacular sights of the island.

The road to the lighthouse (F) lies on a former barrier spit, curving around an area of saltmarsh approximately _ of a mile wide. The roadside pools seen here are borrow pits, the source of soil used for making the road. This spit is of Holocene age, and it parallels the even more recent Nannygoat shoreline where it swings to the northwest along Doboy Sound.

Accretion (building up) can be seen on Nannygoat. The cabana by the roadside which was on the beach in the 1950’s now lies several hundred feet behind the dune line.

As the dunes themselves are capable of movement, so must their flora and fauna be capable of contending with shifting substrate. They do this by a number of strategies. The plants of the foredunes are particularly well adapted to their situation, having a variety of ways to bind the loose sand; extensive vertical or horizontal root and rhizome systems, heavy seed production or a growth pattern which functions as a wind baffle and traps the blowing sand. They must be salt tolerant and capable of withstanding dessication.

The most spectacular dune plant of Sapelo is undoubtedly the sea oats (Uniola paniculata). Not only are they beautiful, but also highly functional in binding the dune structure together. Sea oats are protected in Georgia, and may be collected only by special permit.

Beach elder (Iva imbricata) and panic grass (Panicum amarum) bind the sand, while water pennywort (Hydrocotyle sp.) and morning glory (Ipomoea sp.) form a mat of creepers binding the surface. Perhaps the least pleasant encounters for the unwary barefoot walker are those with the thorns of sandspur (Cenchrus sp.) and prickly pear.

The animals of the foredunes are characterized by their mobility and opportunism. Ghost crabs forage both in the dunes themselves and on the beach, and rattlesnakes or their tracks are often seen among the dunes. Many of the animals are seasonal. There are a wide variety of insects to be seen in the warmer months and, in the more isolated dunes at Cabretta, oyster catchers and other bird’s nest.

More stable interdune habitats are sometimes categorized according to vegetation type. Interdune meadows may be composed of sea oats, beach elder, panic grass, pennywort and further away from the effect of sea salt, prickly pear, Muhlenbergia with its rosy pink heads, and occasionally a tall spike of the Spanish bayonet (Yucca sp.)

Dunes form parallel to the shoreline, and in their lee, shrub thickets form, protected from the wind and salt spray. This pattern is not always readily discernible from ground level, but it provides one of the more spectacular aerial views.

Plants of the shrub thickets are wax myrtle, redcedar (Juniperus sp.), groundsel (Baccharis sp.) and tamarisk. These provide shelter for many of the small birds visiting the island.

The maritime forests contain live oak (Quercus virginiana), redcedar and pines and are the second line of defense against the incursions of the sea. They are well established on “stable” dunes, inland. However, there are some sites on North Nannygoat and Cabretta where the beach has eroded back to the maritime forest.