Drive along the stretch of road from the mid-Cape highway through the Marconi area in Wellfleet, Massachusetts and down to the Atlantic White Cedar Swamp Trail and you will see an extensive sand dune community on both sides of the road. This area is characterized by several hardy plant species including one conspicuous, low-growing, grayish-green shrub called beach heather or poverty grass (Hudsonia tomentosa). This plant is neither a heather nor a grass. It belongs to the rockrose family, the Cistaceae.
Hudsonia is an excellent erosion control agent on dunes. Its deep roots and spreading growth habit help block the removal of sand by wind and rain. It is adapted to this harsh, dry environment and is able to capture and conserve water. From a distance beach heather looks like it grows in dense mats on the sand. A close examination of the leaves reveals a scalelike and alternate arrangement. In early summer it produces an array of small golden flowers that open in the sun. There are five petals and 5-30 stamens. The plant is evergreen and perennial.
The sand dunes are important habitats, not just for xerophytic plants like beach heather, but also for many other species including dusty miller, seaside rose, and beach grass. The sand is deposited from longshore currents, waves, and tides. It is then pushed by the wind and piles up, sometimes forming around solid objects such as rocks or scrub pines. The wind continues to move the fine particles of sand around until it gets trapped by vegetation. Plants such as beach grass have strong, tangled roots which trap sand and allow the deposits to build. In addition, the surface leaves also block the wind from penetrating the surface of the dune.
You can imagine that these systems are very unstable and fragile. While the plants are salt and wind resistant, they are quite vulnerable to trampling. Where dunes front popular beaches people tend to walk over the plants and create foot paths that eventually erode the area. That is why one of the most common and effective management tools is to construct boardwalks over these sensitive areas. People prefer to walk on these platforms and they direct foot traffic away from the plants. Regulations exist on the spacing between boards to allow enough sunlight in for plants to grow under the walkway. In areas already eroded as footpaths, fences can be constructed around them, again framing the area for passage.
Sand dunes are dynamic systems subject to coastal storms, flooding, and erosion. But they are essential habitats that buffer the coastline and protect upland areas.
Copyright Gil Newton 2009 Thanks to Chris Dumas for logo image.