Description of the dune ecosystem

Characteristics of dunes

Along the coast from Zwin in Zeeland to Rottumeroog there is an almost unbroken line of dunes, 300 km long. Characteristic of these coastal dunes is their varied relief, their sandy soils and their marine climate. Proceeding inland from the coast there are gradients in salinity, lime content and age of the soil. These are expressed in a characteristic succession of biotopes: beach, foredunes, open dune valleys, dunes with shrubby vegetation, and the forested landward edge of the dunes. As one proceeds inland the dune vegetation becomes more shrubby (species such as sea-buckthorn and hawthorn). In the dunes there are also pools, swamps, dry and wet grasslands, and heath.

Because of their large variation in soils and biotopes, the dunes are rich in plant and animal species. Some 65% of the Dutch flora is found here and 9% can only be found in the dunes.

Dune land use present and past:

Although the dunes are among the most natural (i.e. pristine) parts of the Netherlands, human influence has been important and continues to be so. In the past the human activities were rabbit hunting, grazing (sheep, goats and cattle), growing potatoes and rye, and the afforestation with conifers. Nowadays the most important uses are water abstraction and recreation.

The area of the dunes

Over time the area of the dunes has decreased because of sand mining, the establishment of bulb fields, residential development, road building and industrial development. Humans have also greatly influenced the biotope composition of the dunes. In recent years, however, the area has remained constant in size.

The dynamics of coast and dunes

The coast is very dynamic by nature: the dunes shift and occasionally the sea breaches them. In the past, people have curbed these processes, primarily by planting marram to stabilise the sea defences and to prevent the dunes advancing inland. Current policy is to encourage the dynamics of the system, by allowing the dunes to be active. And near Schoorl, seawater has been allowed to penetrate behind the first line of dunes.

The drying up and rewetting of the dunes

Until about 1900 there were large damp areas in the dunes. In many locations these disappeared in the first half of the twentieth century, largely as a result of the abstraction of groundwater for drinking water. This drying up of habitats caused dune slack vegetation and its associated butterflies to dwindle.

The abstraction of water from the dunes was superseded by allowing river water to percolate through the dunes. This has led to more open water in the dunes and to the emergence of reed vegetations and their associated birds. The nutrient-rich water also encouraged rank vegetation to develop in the wetter parts of the dunes: species such as great hairy willowherb and nettle have invaded, ousting rare species such as grass of parnassus. Since the 1980s the inflow of nutrients has abated, because the water supply company purifies the river water before pumping it into the dunes.

Thanks to nature restoration projects the area of dune slack vegetation is increasing again. A good example is the Moksloot area on Texel.

The vegetating of the dunes

In the days when people harvested wood and there was extensive grazing, the dune landscape was almost bare. After these practices ceased at the beginning of the twentieth century, and marram was planted and the atmospheric deposition of nitrogen increased, the natural succession accelerated and scrub has encroached - particularly on the calcareous dunes. Fast-growing species like wood small-reed have also encroached in the dune gras vegetation. The decline in rabbit numbers reinforced this vegetation change.

The encroachment of shrubs and fast-growing grasses has major implications for breeding birds and butterflies. Many butterflies have disappeared from the dune grasslands. Breeding birds of open dune habitats are declining, but hedgerow species are increasing. The sand lizard can tolerate some shrub cover and is currently increasing.