The salt marsh in the Danish Wadden Sea is a dynamic landscape, and for thousands of years, people have enjoyed its benefits. 

The salt marsh is the flat, grassy landscape between the higher geest to the east and the tidal flat to the west. It was formed by the tidal waters from the Wadden Sea flooding the flat shoreline and depositing sediments of sand and marine clay, which, over time, have created new fertile land. For thousands of years, the fertile salt marsh has provided a living for a large population of people in the area. That’s why the salt marsh is often referred to as a gift from the ocean.

People on the salt marsh

From early on, people have been drawn to the salt marsh and the opportunities it offers. Traces of early settlements can be found in several places along the coast.  One of them is Hjemsted Banke near the marsh at Ballummarsken, which was home to a settlement as early as 500 BC. The rich salt marsh grass was well-suited for livestock. In the 17th and 18th centuries, trade in bullocks, in particular to the Netherlands, generated substantial income for the farmers in the area. Farmers and tradesmen also benefitted from the location of the salt marsh close to the Wadden Sea, because this is where most of the few natural harbours in Western Jutland are found. Until the second half of the 19th century, the harbours were essential for long-distance transportation. However, because of its location, the salt marsh and its population were vulnerable to the storm surges affecting the Wadden Sea coast since the 12th century and leading to settlements and villages being abandoned.

Land reclamation and dykes

The Frisians were the first to build dykes in the Wadden Sea area. 

The first dykes were low summer dykes, built to protect the soil against the daily high tides. As the storm surges became more common, permanent dykes were required to protect the area, and sea walls were constructed. They were taller and able to keep out the massive amounts of water from the winter storms. They also inhibited the natural dynamics of regular minor flooding, and the salt marsh was transformed into more ordinary arable land. Dyke construction at the Danish Wadden Sea started in Tøndermarsken, where the first sea wall was constructed in 1556. The last dykes, Det fremskudte Dige (the protruding dyke) and the Vidåslusen (the Vidå sluice), were finished in 1981. Many years of land reclamation has made the Vidåen stream 20 km longer, and the ship on the town arms of Tønder is the only remaining testament to the time the town was an important harbour, close to the coast. Ribemarsken, Ballummarsken, Tjæreborg and Darummarsken were all diked in at the beginning of the 20th century.  The only salt marsh area of the Wadden Sea region which has never been dyked-in is the area around Ho Bugt bay. Dyke construction caused problems due to inflowing water from the streams running through the salt marsh. The dykes were constructed with sluices to allow water from the streams to run through the dykes at low tide. However, during prolonged high tides, the sluice gates had to remain closed, and the streams would flood the land behind the dykes. This could happen several times during the winter, and as a result, the soil could not be cultivated in winter time.

Drainage of the salt marsh

The transition of farming activities from bullock to arable farming generated greater interest in more efficient exploitation of the soil on the salt marsh. 

This led to the drainage of Tøndermarsken, which is the only salt marsh in which pumping stations and levees have been built. Thanks to the levees, unlike most other streams, Vidåaen hardly ever overflows its banks. Ballummarsken and Ribemarsken have also been drained off, but only by means of canals.

The salt marsh on fire

However, the drainage of the salt marsh was not without problems. Former wetland plants in the salt marsh have been covered by the muddy water from the Wadden Sea and have transformed into a varied peat layer below the clay soil. If the peat layer is not kept moist, oxygen will enter the peat and cause it to ‘burn’ and subside. This has happened in the salt marsh of Ballummarsken, for instance, where some areas have subsided by up to 75 cm, resulting in the occurrence of large wet areas.

Cultivating the salt marsh

Until the mid-20th century, only a very small part of the salt marsh was cultivated. Instead, the flat grazing areas were used for bullock fattening and hay-making. Cultivation of the salt marsh developed in earnest from the 1950s to the 1970s. Oats was the dominant crop because it could be used as animal feed and was well-suited to moist soil. Furthermore, greater tractor power made it possible to plough the heavy salt marsh soil.

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