Content on this page requires a newer version of Adobe Flash Player.

Get Adobe Flash player
 

  • Nederlands
  • Deutsch
Search in the Encyclopedia

Dieren en planten

Harriers   Hen harrier   Lagomorphs   Rabbit   Voles   Root vole   Plants   Oleaster family   Sea buckthorn   Grass Family   Marram grass   Dune flora   

Water en land

Landforms   Dune areas   Dunes (biotope)   
Dunes in november, Ecomare

Dune areas

Dunes begin where the beach ends. A dune area can consist of one to several rows of dunes. They are fixed mounds of sand, broken up by lower lying regions called dune valleys. A large part of the south-easterern North Sea coast is made up of dunes. These dunes are a natural form of coastal defence, and can be threatened by coastal erosion. Due to the continual influence of the sea and the wind, one finds a unique plant and animal world in the dunes. In addition, dunes are important for recreation and can contain reservoirs for drinking water.

On Texel


, Sytske Dijksen, www.fotofitis.nl

Young dunes and young dune valleys are mostly located on the Hors. Very nice old dunes and dune heaths are found close by Den Hoorn and to the south and north of De Koog. The richest location of sea holly is at the end of the Badweg in De Koog, one of the busiest places on the island! A lovely varied dune landscape with flowery dune fields, steep slopes, small woods and lakes is the Muy.

  • Dune elements

    Dunes consists of many unusual elements: beach ridges, dune grasslands, open dune vegetation, lakes, creeks, marshy and dry valleys, brushwood and woodlands. The notable processes within all the elements are the dune formation, vegetation development, succession and a characteristic water management. Because of this diversity in circumstances, the variation in species is great.
    In the Netherlands, 254 kilometers of the North Sea coastline (40,000 hectare) is made up of dunes. These dunes form only 1% of the total surface area of the Netherlands. Despite the fact that the dunes are only make up a small part of the country, the richness in plants and animals is tremendous: at least 75% of all Dutch plant species grow here and 140 of the around 190 species of Dutch nesting birds brood in the dunes.

  • Calcium

    There are two categories of dune regions in the Netherlands: the calcium-rich southern European dunes and the calcium-poor northern European dunes. The boundary between these two regions can be precisely mapped and lies in North-Holland, by Bergen aan Zee. The difference in two regions has to do with the nutrients. There are more nutrients in the ground south of Bergen aan Zee than north of it, where the dunes formed much later. The presence of nutrients determines whether a plant can grow or not.

  • Sand

    The sand of the southern dunes has been transported by the rivers Rijn, Maas and Schelde. Originally, this sand came from the bedrock in the mountains of Central Europe. It is generally yellow or brownish in color (blond dunes) and is rich in minerals such as calcium. The northern dunes were formed from sand coming from the North Sea floor, which was blown in during the Weichsel period. This is the same kind of wind-borne sand desposits found in Drenthe, southeastern Friesland, Overijssel, Gelderland and North-Brabant. It is greyish white in color and is poor in minerals.

  • Dune formation
    The formation of a new dune, Ecomare

    Sandy beaches and dunes can only form along coasts that are not too steep and where there is a sufficient supply of sand on the sea bottom. There must be a predominant onshore wind. Even small height differences on a beach can be enough to start dune formation. It is less windy behind a small height, where drifting sand can land and stay put. As long as the wind does not blow too hard nor that the dune washes away, it will continue to grow.
    Dune formation is accelerated by the first beach flora. Pioneer plants catch drifting sand with their leaves, where it falls on the leeward side of the plant. When there are enough plants to help catch sand, slowly but surely a small dune evolves as the number of plants catching . Sand couch is the first plant to start the process. When the dune has grown around one meter in height, rainwater will be retained in a freshwater bubble under the surface, allowing other plants to grow. Marram grass and blue lyme grass now start to dominate the scene. Marram grass has the tendency to grow just as quickly as the dunes, fixing the sand with its root system. As soon as a dune is overgrown with marram grass, it can only be eroded away by the sea during extremely high tides and strong wave action.
    The young dunes can grow together into a new beach ridge with new dune valleys forming on the land side. One finds impenetrable prickly bushes of sea buckthorn in the shelter of the first row of dunes. Sea buckthorn is an important dune plant because it deposits nutrients (nitrogen) via its root tubers into the ground. The buckthorn uses some of the nutrients again for itself, however enough remains for other plants to flourish. Thick bushes of elder and a ground cover of stinging nettles and blackberries are the result. The degraded leafage from these plants provides even more nutrients, allowing grasses and moss to develop; at this point, an end has come to drifting sand.

  • Wild growth, eutrophication and dessication
    Dealing with overgrown, nutrient-rich dunes , Ecomare

    Two environmental developments have had an important influence on nature in the dunes in the 1980s and 1990s: dessication due to water extraction and coastal erosion and eutrophicaiton due to an increase in the supply of nitrogen compounds. The combination of these two developments in particular have led to an increase in grasslands in many dune regions.
    Grey hair-grass vegetation, characteristic for relatively young nutrient-poor dry dunes, have disappeared in many places to make room for other grass vegetations which are notably less rich particularly in moss and lichen species. Grass of Parnassus vegetation (with very rare orchids and gentian species), characteristic for young nutrient-poor wet dune valleys, is also growing more scarce.
    The consequences of increased grasslands in the dunes is also disastrous for many bird species. For example, there was a sharp decline in the curlew population between 1984 and 1994. In that same period, the common redpoll was only able to maintain 3% of its nesting pairs and the skylark and northern wheatear declined drastically (between 50 – 70%). They made room for species which prefer a landscape with bushes and trees, such as the whitethroat and the chiffchaff.
    The sand lizard population has declined significantly due to a lack of open, wind-blown dunes. Many butterflies that used to be found in damp dune valleys, such as the marsh fritillary, have since grown scarce.
    In many dune regions, these problems are being tackled with large-scale management regulations: removing the top layer of soil where vegetation in valleys have become overgrown (such as in the Muy on Texel), raising the groundwater level (for example in the Moksloot area also on Texel) and allowing the wind to further develop dunes that had been made stable (particularly on Terschelling and Schiermonnikoog). Large grazers (ponies, goats and cattle) have also been introduced in many areas to combat overgrowth.

  • Protection of Dutch dune regions
    Dunes on Texel, Ecomare

    Every province has been requested to make a TOP-list of nature areas that will receive priority in combatting dehydration.The province of North-Holland has included practically the entire dune coast of North-Holland in its TOP-list. Some of the areas fall under the Ecological Main Structure, whereby grounds must be purchased from individuals in order to realize the goal. The province hopes that at least 90% of the goal is achieved by 2013.
    According to the Nature Policy Plan from 1990, all Dutch dune areas would fall under the Nature Protection Act by the end of 1998. This resolution has not nearly been reached. By 31 December 1998, only 41% of the dunes were legally under protection. Most of the successes were made in Zeeland: 90% of the dune areas were protected by the target date. In South-Holland, the percentage was 30% and in North Holland, 45%.
    The backlog on the Wadden Islands was also large: only 31% of the dune areas fell under the NP plan by the end of 1998.
    In general, one attributes the slow allocation tempo to two causes. First of all, one has been hesitant to assign areas since the Nature Protection Act would be revised in 1999. And more important was the 'lack of public support' for legal nature protection. There are many influences (agrarian, industrial, recreational and military influences) on a local and regional scale not in favour of the law. A good example is the situation on Texel. The government used the possible allocation of the Nature Protection Act as a means of coercion to acquire cooperation from local interest groups for establishing the National Park 'Dunes of Texel'. The National Park status is a much weaker protective instrument than the Nature Protection Act.