The Wadden Sea landscape

tide & landscape

THE WADDEN SEA LANDSCAPE A MIX OF SEA, SAND, MUD AND MUCK

Undisturbed marshland around Ho Bay and Varde River Valley The area of the Wadden Sea represents merely a small piece of Denmark, but some of the country’s (maybe the world’s) most exciting and dynamic square kilometers - also in an international perspective.

The Wadden Sea is the area between a total of 23 Wadden Sea islands and the mainland that stretches 500 km from Blåvands Huk in Denmark to Den Helder in the Netherlands. Thus, the Wadden Sea, with its ca. 8.000 km2 is the longest unbroken stretch of sand and mudflats in the world, of which 850 km2 are Danish.

This area is created by a combination of the changing Ice Ages’ deposits of sand, gravel, tides, waves, mud, plants and an unbelievable amount of animal excrements. Not until far in the development of the Wadden Sea did a very different, but decisive factor become evident - man’s striving for new land and protection.

The ice sowed the seed

The early history of the Wadden Sea is marked by the last two Ice Ages, when enormous sheets of ice covered large areas of Northern Europe, changing the landscape beneath and in front of it.

The previous Ice Age (Saale) topped 140,000 years ago and covered large parts of Northern Europe.

When the ice retreated, the current Wadden Sea

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area looked like a hilly landscape as we know it from eastern Denmark. The water level rose and the area took the form of a coast landscape with bays, straits and belts. The remains of this landscape, the moraines, the elevated areas along the Wadden Sea, have their own local name: the Geest.

The last Ice Age (Weichsel) ended about 11,500 years ago, but this time the ice ”only” reached to 80km east of the Wadden Sea area. The North Sea area had dried and become tundra covered by lichen, herbs and dwarf bushes. The plants attracted, among others, reindeer and aurochs which bought the first Stone Age hunters to the area.

From the ice sheet rose rivers of meltwater that paved the way between the moraines, bringing sand and gravel towards the Ice Age ocean. The huge amounts of sand and gravel became a thick, even layer of a westerly sloping cover between the moraines and gave the landscape the character of flat tundra.

Ulrik G. Lützen, Vadehavets Formidlerforum & Søren R. Jessen, Naturstyrelsen Vadehavet Translation: Nanna Mercer, Sirius Translation

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tide & landscape

Previously mud fences were built to keep back sand and clay in order to speed up the natural processes.

The islands are formed

When, once again, the ice lost its grip on the land, the oceans rose once more and, ca. 8,000 years ago, flooded the Stone Age people’s hunting grounds, i.e., the North Sea. Nature, the tides, the winds and the waves took over and formed the landscape. The North Sea waves bought the sand from the huge meltwater floods back towards the coast where, among other things, it became large expanses of sand. With time, the sandy expanses reached an elevation where flooding was rare and another of the Wadden Sea landscapes was born - the sandflats.

On the now drier sandflats, plants that could catch drifting sands between their stems migrated from other regions. That is how the first dunes were formed and thus, the Wadden Sea islands.

Island location is dependent on the range of the deep Wadden Sea tidal gullies. In Tyske Bugt, the central part of the Wadden Sea, where the tides reach their maximum range of 4m, the tidal gullies lie too close for there to be room for islands. In the Danish part of the Wadden Sea, where the tidal range is lower (1½2m) these gullies are positioned far enough apart to allow room for the islands, Rømø, Mandø and Fanø, plus the peninsula, Skallingen.

The places where the islands were formed functioned as barriers against the rough waters from the North Sea, thus protecting the hinterland.

New material for the Wadden Sea Every year, approximately 70 million tons of clay and sand is moved into the Wadden Sea, but only 3.5 percent of it is deposited.

Accumulation of plant growths and animals

In the Danish part of the Wadden Sea, water washes through the tidal gullies at a rate of ca. 2 km3 at every tide, bringing huge amounts of sand and clay into the lagoon between the islands and the mainland. About 3 to 5 percent of this material is deposited in calmer waters and even clay particles have a chance of coming to rest here, helped in large measure by the plant and animal life in the Wadden Sea. On the mudflat live large numbers of soil animals such as mussels and snails that filter the water particles in their own search for food. These fine particles move though the animals and exit as courser particles.

Course particles are more difficult for the waves and the current to move around and the animals therefore have a significant share in keeping the mudflats resistant to the erosion caused by the waves.

On the side facing east on the islands and between the hilly moraines, the marshland emerged when salt-tolerant plants like glasswort immigrated to the higher areas of the wadden. With tidal flooding, the plants retain the clay particles not only on but also

Ulrik G. Lützen, Vadehavets Formidlerforum & Søren R. Jessen, Naturstyrelsen Vadehavet Translation: Nanna Mercer, Sirius Translation

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tide & landscape

The deepening of the shipping channel through Grådyb has upset the natural balance of erosion/deposition. between the stems by lowering the speed of the water. The material retained by the plants helps to elevate the marshland by approximately 4mm per year on average.

Mankind

The rich and fertile marshland has always attracted man, who settled on the elevated Geest where he was somewhat secure from storm surges. As further protection against the sea, medieval man built the first dikes in Tøndermarsken. Today, the only undiked marshland is that surrounding Ho Bugt and Varde Ådal, and thus most of the marshland has been deprived of its natural development with yearly flooding and inflow of material.

In tandem with technological progress and its many possibilities, man’s imprint on the land started in earnest. The dredging of the channel through Grådyb

by Esbjerg, plus the dams built by Rømø and Sylt are examples of infrastructure that has shifted the natural balance between the erosion and the sedimentation of vast areas.

The future

Today, in the Wadden Sea, the sea level rises by ca.

2.2mm per year, which means that in most places the marshland can keep up with the rising ocean.

Dredging of Grå Dyb Esbjerg Harbor was built, in part, because of the advantageous access it afforded ships though Grå Dyb, but with still larger and more depth-demanding ships, it became necessary to dredge the channel. This has shifted the natural development in the area, and the coasts on Skallingen’s southern point and on Fanø’s northern tip are receding, since they deliver the material that waves and currents bring in to refill the channel.

The dams changed the landscape By building the dams to Rømø and to the German island Sylt, the tidal area around Listerdyb was trapped, thereby changing the tidal and current conditions.

Researchers are therefore cautiously optimistic that the marshland and the wadden can keep up when the ocean in the future begins to rise even faster.

The Wadden Sea and the dynamic behind it very complex and one thing is certain - the landscape will not remain as we know it - today.

The Wadden Sea has never been and will never be stable, for this is a landscape forever changing.

Ulrik G. Lützen, Vadehavets Formidlerforum & Søren R. Jessen, Naturstyrelsen Vadehavet Translation: Nanna Mercer, Sirius Translation

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tide & landscape

Things to do Moraines - can be seen in for example Hjerpsted and Marbæk.

Sandflats - Koresand west of Mandø and Jordsand opposite Hjerpsted.

Mudflats - The Wadden Sea mudflats can be seen by Ballum, Emmerlev Klev, Juvre on Rømø and from parking areas between Kongeåen and Sneum ÅUndiked marshland - around Ho Bugt, up towards Oksbøl, on Skallingen, and in Råhede

Learn about the landscape here ..

NaturKulturVarde

Gl. Skovfogedbolig Roustvej 111 DK-6800 Varde T: +45 75 22 22 50 E: nkv@naturkulturvarde.dk W: www.naturkulturvarde.dk

Varde Museum Kirkepladsen 1 DK-6800 Varde

T: +45 75 22 08 77 E: vam@vardemuseum.dk W: www.vardemuseum.dk

The Fisheries and Maritime Museum Tarphagevej 2-6 DK-6710 Esbjerg V. T: +45 76 12 20 00 E: fimus@fimus.dk W: www.fimus.dk

Vadehavscentret Okholmvej 5 Vester Vedsted DK-6760 Ribe

T: +45 75 44 61 61 E: info@vadehavscentret.dk W: www.vadehavscentret.dk

Museum Sønderjylland - Højer Mølle Møllegade 13 DK-6280 Højer

T: +45 75 44 61 61 E: hoejer@museum-sonderjylland.dk W: www.museum-sonderjylland.dk/hojer-molle.html

Naturcentret Tønnisgård Havnebyvej 30 DK-6792 Rømø T: +45 74 75 52 57 E: info@tonnisgaard.dk W: www.tonnisgaard.dk

tips for further reading

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The salt meadows in the Wadden Sea The Tide and the Wadden Sea Storm surges on the Wadden Sea coast Life on the waddens

About Vadehavets Formidlerforum...

Vadehavets Formidlerforum is a partnership of visitor centers that mediate the Wadden Sea’s natural and cultural heritage.

VFF’s main activity is to coordinate projects that highlight the nature and culture heritage of the Wadden Sea..

Learn more at www.vadehav.dk

Ulrik G. Lützen, Vadehavets Formidlerforum & Søren R. Jessen, Naturstyrelsen Vadehavet Translation: Nanna Mercer, Sirius Translation

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