Legend has it that motherly sea giantess Neringa created the spit, lovingly carrying armfuls of sand in her apron to form a protected harbour for the local fishing folk. The truth is as enchanting. The waves and winds of the Baltic Sea let sand accumulate in its shallow waters near the coast 5000 or 6000 years ago to create an original beauty found nowhere else.

Massive deforestation in the 16th century started the sands shifting. Trees were felled for timber, leaving the sands free to roam unhindered at the wish of the strong coastal winds. At a pace of 20m a year, the sands swallowed 14 villages in the space of three centuries.

Dubbed the 'Sahara of Lithuania' due to its desert state, drastic action was needed. In 1768 an international commission set about replanting. Today this remains a priority of the national park authorities. Deciduous forest (mainly birch groves) covers 20% of the national park; coniferous forest, primarily pine and mountain pine trees, constitutes a further 53%. Alder trees can be found on 2.6 sq km (3% of the park's area). Lattices of branches and wooden stakes have pinned down the sand.

But the sands are still moving - 5.5m north in 2002 and at least 1m a year since. Slowly the spit is drifting into the Baltic Sea. Each tourist who scrambles and romps on Parnidis Dune - the only remaining free-drifting dune - meanwhile pushes down several tonnes of sand. With 1.5 million people visiting the dunes each year, the threat of people wandering off designated paths - not to mention forest fire - is high.

The dunes are also shrinking. Winds, waves and humans have reduced them by 20m in 40 years. Its precious beauty may yet be lost forever.