Marram Grass and Dune Stabilization in Italy

How Ammophila Traps Sand

Ammophila arenaria tolerates sand burial better than most plants. As wind-blown sand accumulates around its stems, the plant responds by growing upward and extending lateral rhizomes. This creates an expanding root network that binds loose particles from below while the above-ground stems slow wind speed and cause further deposition. The result is a self-reinforcing mound — the foredune — that grows as long as the grass remains vigorous.

The mechanism depends on continuous low-level sand supply. Without fresh burial, marram grass gradually loses competitive advantage and weakens. This characteristic, known as psammophily, means the plant's health is directly tied to an active beach-dune sediment exchange. Interrupting that exchange — through beach nourishment programs that alter grain size, or through management that eliminates the dry backshore zone — can undermine the grass without any direct physical removal.

Dune Zonation in Italy

Italian coastal dunes typically follow a zonation from sea to inland. The primary zone, closest to the water, is dominated by strandline species tolerant of salt spray and intermittent flooding. Immediately behind it, Ammophila arenaria forms the characteristic foredune. Further inland, where sand movement is reduced, a more diverse scrub community develops — in Italian coastal habitats, this often includes species such as Juniperus macrocarpa, Pistacia lentiscus, and Phillyrea angustifolia, depending on the region and climate.

This zonation is recognized in the European Habitats Directive, which lists several dune community types as Annex I habitats requiring specific conservation status. Habitat type 2110 (embryonic shifting dunes) and 2120 (shifting dunes with Ammophila arenaria) both occur along Italian shores and trigger assessment obligations under national transposition of the Directive.

Effects of Degradation

The consequences of marram grass loss follow a recognizable pattern. Without the foredune, the transition from open beach to stable land is abrupt. Storm waves that previously expended energy climbing and reworking the dune face now reach the flat surface directly, carrying sediment offshore. The beach face narrows. In some documented cases along the Adriatic, loss of foredune vegetation preceded beach loss of several meters per decade.

Trampling is one of the most common causes of degradation. A single informal path through a foredune creates a blowout — an erosional notch — that widens under continued wind action. Once the blowout reaches the back of the dune, wind funnels through and the surrounding vegetation is progressively undercut. Fencing and defined access paths are the standard management response, though their effectiveness depends on consistent enforcement and maintenance.

Restoration Practice

Restoration of degraded foredunes most commonly involves replanting with locally sourced Ammophila arenaria propagules, combined with low-cost brushwood fencing to trap sand and reduce wind velocity while the plants establish. The fencing — typically constructed from dead branches or reed — slows airflow and causes sand to accumulate around the young plants, mimicking the natural burial stimulus the species requires.

Italian restoration projects, including work carried out under coastal habitat management programs in Sardinia and parts of the Adriatic coast, have documented recovery of foredune structure within three to five growing seasons under favorable conditions. The critical variables are sediment availability, absence of continued disturbance, and the use of locally genotyped plant material that matches local morphological and phenological characteristics.

Effective dune restoration requires not only planting, but also managing the conditions that allowed degradation in the first place. Plant material without visitor management, fencing, or adequate sediment supply rarely results in durable recovery.

Regulatory Context

In Italy, dune vegetation removal requires authorization from the relevant Soprintendenza where landscape constraints apply, as well as assessment under the national environmental impact framework for interventions affecting Habitats Directive sites. Regional protected area plans in Sardinia, Apulia, and along the Adriatic include specific provisions for foredune management, restricting vehicle access, commercial clearing, and other activities incompatible with dune stability.

ISPRA's national coastal monitoring program tracks shoreline position and dune extent, providing a baseline against which management interventions can be evaluated. The data are publicly accessible through the ISPRA portal and have been used in regional coastal planning documents.