The fore-dunes of Poland's Baltic coast are not stable geological features — they are dynamic accumulations of wind-blown sand, continuously shaped and reshaped by wind, wave action and plant growth. The primary biological agent of dune building along this coast is Ammophila arenaria, European marram grass, a species whose growth response to sand burial is central to its ecological function.

Why Marram Grass Builds Dunes

Ammophila arenaria is a perennial tussock grass with a distinctive and ecologically critical trait: when sand accumulates around its stems, it responds by growing upward at a rate that roughly matches the burial. This is not passive tolerance but an active growth response — buried shoots produce adventitious roots in the deposited sand, and new tillers emerge above the new surface level. The plant effectively grows with the dune it creates.

On beaches where sand supply is adequate and wind direction consistent, this mechanism results in the gradual vertical accretion of fore-dune ridges. The root and rhizome mass within the dune increases with each season, binding the sediment and reducing its mobility. Measurements at long-term monitoring sites in Denmark and the Netherlands — coastlines comparable in sand supply to the Polish Pomeranian coast — suggest fore-dune accretion rates of several tens of centimetres per year under favourable conditions, though local figures vary considerably.

Distribution Note

Ammophila arenaria occurs naturally across Atlantic and Baltic Europe. On the Polish coast it is the characteristic fore-dune grass from the German border (Świnoujście area) east to the Hel Peninsula and the Gulf of Gdańsk. The species has been introduced as a dune stabilisation tool in parts of North America, South Africa and New Zealand, where it is now invasive.

The Structure of a Marram Dune

A mature marram-dominated fore-dune has a characteristic vertical and horizontal structure. At the seaward base, where disturbance from wave swash is frequent, plant cover is sparse and patchy. Higher on the dune face, where sand deposition is greatest, marram forms dense stands with vertical leaf blades that deflect wind upward, causing further deposition on the crest. Behind the crest, where sand movement is reduced and the environment more sheltered, marram plants become less vigorous and are increasingly accompanied by other species.

The leaf blades of marram grass roll inward along the midrib under drought stress, reducing transpiration surface and enabling the plant to persist during summer dry periods when the surface sand can reach temperatures lethal to most herbaceous vegetation.

Dune Succession on the Polish Coast

Behind stabilised marram fore-dunes, a longer-term succession proceeds as organic matter accumulates, soil develops and wind exposure decreases. The characteristic vegetation sequence on the Polish Baltic coast includes:

  • Embryo dune: sea rocket (Cakile maritima), sand couch (Elytrigia juncea)
  • Fore-dune: marram grass (Ammophila arenaria) dominant, often with lyme grass (Leymus arenarius)
  • Grey dune: marram declining, sand sedge (Carex arenaria), mosses and lichens increasing
  • Fixed dune: diverse grassland with red fescue (Festuca rubra), wild thyme and various herbs
  • Dune scrub: sea buckthorn (Hippophae rhamnoides) dominant, particularly frequent on Polish dunes
  • Dune woodland: Scots pine (Pinus sylvestris), often planted historically for dune fixation

Sea buckthorn, a nitrogen-fixing shrub, spreads aggressively on stabilised Polish dunes and alters the soil chemistry of the fixed dune zone. Its management is a recurring question in the nature conservation of dune systems within Natura 2000 sites.

Management and Planting Practice

On exposed sections of the Polish coast where dune erosion threatens infrastructure or the integrity of coastal habitat, marram grass is used in active dune restoration. Transplanting of marram tussocks or sowing of seed is carried out on eroding dune faces. Brushwood fences — sometimes called sand fences or sand traps — are installed to slow wind velocity near the surface and encourage initial sand deposition before vegetation is established.

The Polish State Forests (Lasy Państwowe) and the Maritime Office (Urząd Morski) are the principal agencies involved in coastal dune management along the Polish Baltic coast. Dune stabilisation work is documented in the management plans for coastal Natura 2000 sites, which are publicly accessible through the Polish General Directorate for Environmental Protection (GDOŚ).

Further reading: GBIF — Ammophila arenaria; Encyclopedia of Life — Ammophila.