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Sand dune - Country Report, Denmark

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This article on the sand dunes of Denmark, is a revised country report from the 'Sand Dune Inventory of Europe' (Doody ed. 1991) [1]. The 1991 inventory was prepared under the umbrella of the European Union for Dune Conservation [EUDC]. The original inventory was presented to the European Coastal Conservation Conference, held in the Netherlands in November 1991. It attempted to provide a description of the sand dune vegetation, sites and conservation issues throughout Europe including Scandinavia, the Atlantic coast and in the Mediterranean.

An overview article on the distribution of European sand dunes provides links to the other European country reports. These represent chapters from updated individual country reports included in the revised, 2nd Edition of the 'Sand Dune Inventory of Europe' prepared for the International Sand Dune Conference “Changing Perspectives in Coastal Dune Management”, held from the 31st March - 3rd April 2008, in Liverpool, UK (Doody ed. 2008)[2].

Authors: J Patrick Doody & Peder Skarregaard, with minor revisions 2007; additional information Bird (The World’s Coasts: Online, [1] )


Introduction

The western shores of Denmark include extensive dune landscapes. Dunes also occur inland and on the east coast mainland and the islands, although here they are much smaller and more widely scattered. This report only considers the coastal dunes, of which there are some 80,000ha. 30,000ha of these have been afforested. The data presented below come from a variety of published sources. The map shows the estimated total area of dune, based on (Kuhlman 1969) [3].

Distribution and type of dune

Much of the coast of Denmark is bordered by a post-Litorina marine foreland, a lowland fringe that often includes beach ridges and dunes formed at intervals during the fall of sea level. Sand deposition has occurred on a large scale on the North Sea coast from the west coast of Jutland southward along the German, Dutch and Belgian coasts, largely derived from glacial drift on the sea floor, swept eastward by waves generated by the prevailing westerly winds.

Onshore winds have formed extensive transgressive dunes (klit) behind beaches on the west coast of Jutland, and locally elsewhere. There is evidence of past phases of dune stability, when a vegetation cover developed, and instability when this weakened. Clearance of woodland, grazing and cultivation have led to activation of drifting sand areas in recent centuries, and spilling dunes have buried old buildings, roads and farms. An attempt to protect dune vegetation made in a parliamentary Act of 1539 was only partly successful. Subsequently, trampling by holidaymakers and damage by their vehicles also resulted in blowouts. Drifting of wind-blown sand became severe on the west coast of Jutland, exposed to strong prevailing westerly winds. There have been various historical attempts to stabilise drifting sand by making fences and planting grasses and trees, and intensification of these in recent decades has greatly diminished drifting of wind-blown sand (Møller 1985)[4].

Today the sand dunes of Denmark are not only extensive, but also include some of the most active dune landscapes in Europe. The last big period of sand drift began about 500 years ago and in places, they have moved inland by some 8-10km. It is because of this movement and the overwhelming of villages, that planting took place over large areas with exotic species of pine. The dunes on the northwest coast are up to 30m high with a seaward facing, eroding dune front backed by extensive parabolic dunes. In the south the dunes are lower, less than 20m, have more stable forms, with transitions to saltmarsh.

Large scale sand deposition has formed beaches and dunes in the northern part of Køge Bugt, and on the east coast of Zealand the peninsula of Feddet is a broad depositional foreland with numerous successively-formed sandy beach ridges tapering southward in recurved spits, the eastern fringe being overlain by dunes. On the island of Langeland, sandy beaches backed by dunes with wild rose scrub occur at Ristinge Hale.

On the northeast coast of Jutland, beach ridges and dunes occur on a blunt foreland at Nordstrand, and return in the 35m high cliffs at Stavnshoved. North of the mouth of Mariager Fjord, the Odde coast has prograded with the addition of dune ridges, deposited in the latter part of the nineteenth century on nearshore sand flats. Onshore winds during low water phases built coastal dunes, which were planted with pine forests and stabilised. To the north, Hurup has sandy beaches with a white shelly upper beach above normal high tide level, backed by low grassy (Elymus) dunes. In northernmost Jutland Skagen is a low-lying peninsula of glacial drift fringed by beaches and dunes, formed as the result of post-Litorina Sea uplift of about 15m. North of the port of Frederikshavn, there are alternations of sandy beaches and low dunes with marshy sectors. Much of the coastline has been receding in recent decades, but a dune ridge has grown higher at Ålbeck, and at Sandmilen westerly winds have driven dunes that are spilling on to the eastern shore.

On the island of Anholt, a hill of glacial drift is bordered eastward by a broad heathy sand and gravel plain (Ørkenen), with beach ridges and patchy dunes. Flakket, a lobate foreland on the north coast, has a western fringe of grassy dunes, and on the south coast are cliffed dunes in which bedded beach gravels are locally exposed.

A sheet of blown sand covers much of the island of Laesø where the wind has re-worked glacial drift. There are beach ridges and patchy dunes under heath and woodland, and there are higher dunes on the northern coast, where dunes back a prograded sandy beach (Vester Nyland) and low cliffs have a capping dune ridge. On the south coast, the elongated barrier island of Knotten carries a developing ridge of grassy dunes.

In northern Jutland, the north coast of Grenen (Nordstrand) has an extensive sandy plain, frequently overwashed by storm surges from the North Sea. To the south-west, past Højen, is a widening backshore zone of hummocky dunes, mostly held by grassy vegetation but with some blowouts. Their seaward margin is truncated by sand cliffs in which gravel deposits are exposed. At Råbjerg Mile an area of dunes up to 40m high has been deliberately left unvegetated, and is advancing eastward at about 10m/year. South of Hirtshals in northwest Jutland a dune fringe widens behind a firm sandy beach, the Liver Å flowing through them to the sea near Tornby Strand. Rubjerg Knude is a slight salient with a steep cliff cut in glacial sands and clays capped by peat and a landward-spilling cliff-top dune. At Kollerup Strand coastline recession and landward movement of dunes occurred following gravel extraction from the beach and backshore area. North of Klim the low-lying sandy coast carries large parabolic dunes that have migrated eastward. A sandy beach backed by dunes faces the North Sea, and is subject to erosion in winter and accretion in summer, as well as eastward longshore drifting, but there has been overall recession of the coastline. A long gently curving sandy beach backed by eroding dunes with many tumbled blockhouses (dating from the 1940-45 era of German occupation) runs behind Vigsø Bugt and out to Chalk bluffs towards Hantsholm.

South west of Hantsholm the coast is low-lying and fringed by grassy dunes through which flow a number of small streams draining from reedy lakes, Nors Sø and Vandet Sø, inland. The dunes are generally cliffed behind the sandy beach, with some exposures of peaty horizons and lacustrine sediments indicating that they have moved landward over marshes and lakes. The hinterland is a rather barren area of dunes and heathland. To the south, the dune fringe widens, and drifting dunes had overwhelmed farmland and a church at Lodbjerg before they were stabilised in the 19th century.

In northwest Jutland, there has been accretion on the beach on the western side of the harbour at Hornbaek, where the soft white sand is backed by dunes with thickets of the wild pink rose, Rosa rugosa. Low dunes and the heathy woodland of Tisvilde Heen, originally planted to halt the drifting of wind-blown sand, back the sandy beach at Tisvildeleje.

In southwest Jutland Nissum Fjord is a coastal lagoon enclosed by a straight dune-capped barrier with an entrance at Torsminde in the centre. To the south dunes drift inland towards Husby. The inner, older dunes carry pine forest on podzolic soils, but the outer dune is spilling landward over these as the coastline recedes. The dunes continue along a barrier fronting small lagoons and Ringkøbing Fjord. South of Nymindegab the dune fringe continues past Henne Strand, backed by a heathy sand plain. Behind the wide, firm beach at Vejers Strand, the dune fringe widens southward to the foreland at Blåvands Huk. Here the coast swings south eastward and the backshore dunes are cliffed and receding about 3m/yr (Bird 1974)[5].

The islands of Fanø, Mandø and Rømø are essentially barrier islands, with beaches and dunes over glacial drift. Fanø has a wide low tide sandy beach and grassy dunes along its western coast. Rømø also has a wide beach at low tide on the western shore, backed by an irregular high tide shoreline and grassy dunes.

On the south coast of the Danish island of Bornholm, a white quartzose sandy beach runs out to Duedodde, the southernmost point, where pine forests back the sand dunes.

Although large areas of dune have been artificially stabilised as a deliberate and long established policy designed to prevent the shifting sands from destroying farmland and villages a few important areas of mobile dune still survive. The dunes have developed on a coastline, which is rising relative to sea level in the north, whilst sinking in the southern part of the country by 1-2mm per year, because of isostatic adjustment. The calcium carbonate content of the sand is generally low and this is reflected in the predominantly acid vegetation, which dominates the unafforested dune.

Vegetation

Much of the vegetation in the unafforested dune is composed of either mobile; Ammophila dominated yellow dune or dune heath, with only a few areas with oak scrub. Undoubtedly grazing took place in former times and may have helped destabilise mature dunes and contribute to the extensive sand movement, which has occurred in the past. Today the vegetation is a product of the combined effects of past human exploitation and natural sand drift.

Foredune

Extensive areas of Ammophila arenaria is the predominant foredune and dune building vegetation type. Skagen in the north represents the most extensive area of mobile dune in Denmark.

Acid Dune grassland

Dunes with Carex arenaria and Corynephorus canescens develop in a sometimes lichen rich dry dune.

Dune heath

This includes dry dune heath with Calluna vulgaris and Empetrum nigrum and wetter areas with Erica tetralix.

Woodland

Areas of native scrubby oak (Quercus robur) woodland on dunes appear to be 400-800 years old and pre-date the dunes that have buried them. One of the few examples occurs near Skallingen.

Swamp (Dune slacks)

Stands of Phragmites australis and Scirpus maritimus occur in wet dune slacks.

Afforested areas

Various species of conifer are the most frequently planted trees. These include mainly Picea sitchencis, and the pines Pinus mugo, P. sylvestris and P. contorta.


Important sites

Figure: Map of sand dune distribution and important sites in Denmark. Copyright: J Pat Doody

The dune landscapes along the western shores of Denmark are unbroken from Skagen (Site 1) to Skallingen (Site 3), a distance of about 300km. The dunes range from 100m to 8-10km wide. Four sites provide important examples of natural and semi-natural dune habitat. In the north, the untamed landscape of the Skagen is obviously important. In the south, in the northern part of the Wadden Sea, Rømø has extensive dry and wet dune heath with transitions to saltmarsh. The extensive area of dunes point to the fact that there are numerous sites of importance on a European scale though not all are identified here.

Figure: List of some of the most important sand dunes in Denmark.

NR, Nature Reserve. NB The areas given in the table represent the total for the whole site including saltmarshes, mud flats, lakes and other adjacent habitats.

Conservation

Past management and over-exploitation of the dune may be partly responsible for the major instability, which combined with a natural tendency for landward movement under the influence of the prevailing westerly winds, lead to considerable effort on sand stabilisation. Today regulation of the use of the dunes is through a special law of protection. There is no grazing and from 1935, no new summer cottages are allowed in the protected dunes. Seven state forest districts, under the National Forest and Nature Agency of the Ministry of Environment, are responsible for sand dune management. Today there is recognition that dune areas have an intrinsic value, which is often hidden by pines. Therefore, regeneration projects are underway, which aim to convert pine plantations into natural dune landscapes. A Life-funded project [2] set out to restore dune habitats along the Danish West Coast.

Given the preoccupation with prevention of sand drift, in the past, full recognition of the conservation importance of the more natural dune forms was not always recognised. The exceptions were Skagen and Hanstholm. Dune heaths were used to graze sheep or for harvesting feed and fuel on a regular basis. This kind of management ended some time ago. In time, this caused the varied nature of the dune heaths to diminish, and the number of species living there to decline. The Life project promotes harvesting/mowing, grazing, or small-scale burning as a means of maintaining the heath.

In areas heavily overgrown with conifers, their removal is essential in order to establish coherence with the adjacent open dune landscapes. The management also improves habitat conditions for plants and animals, which depend on a mosaic of wet dune slacks and dry dunes.

Original contact: Peder Skarregaard, DENMARK.

Additional information

Ecosystems of the World 2A Dry Coastal Ecosystems, Polar regions and Europe (Jensen 1993)

Jensen, A., 1993. Dry coastal ecosystems of Denmark. In: Ecosystems of the World 2A Dry Coastal Ecosystems, Polar regions and Europe, ed., van der Maarel, Elsivier, 183-192.

Dijkema, K.S. & Wolff, W.J., 1983. Flora and Vegetation of the Wadden Sea Islands and Coastal areas, Report No.9 of the Wadden Sea Working Group, Netherlands.

References

  1. Doody, J.P., ed., 1991. Sand Dune Inventory of Europe. Peterborough, Joint Nature Conservation Committee/European Union for Coastal Conservation.
  2. Doody, J.P., ed. 2008. Sand Dune Inventory of Europe, 2nd Edition. National Coastal Consultants and EUCC - The Coastal Union, in association with the IGU Coastal Commission.
  3. Kuhlman, H. 1969. Klitlandskaber, recente. Havklit, indsande. Norget Skematisk Afgrænset.
  4. Møller, J.T., 1985. Soil and sand-drift in Denmark. Geoskrifter, 22, Geologisk Institut, Aarhus Universitet.
  5. Bird, E.C.F., 1974. Coastal changes in Denmark during the past two centuries. Skrifter i Fysisk Geografi, Institute of Geology, University of Århus.


See also


The main author of this article is Doody, Pat
Please note that others may also have edited the contents of this article.