The landscape of the Wadden Sea

From Denmark to the Netherlands

The Wadden Sea stretches from Blåvands Huk in Denmark to Den Helder in the Netherlands - a distance of around 500 kilometres. There are 23 Wadden Sea islands in total, and the Wadden Sea consists of the islands and the entire area between these islands and the mainland. The area is the longest stretch of eroded sand and mudflats in the world. This unique area was formed by a combination of glacial deposits, tides, waves, wind, sand, mud, plants and an unimaginable amount of animal faeces. It wasn't until late in the Wadden Sea's development that humans began to shape the landscape in their search for new land and protection.

Ice laid the foundation

The Wadden Sea's very early history is characterised by the last two ice ages, when huge ice sheets covered large parts of Northern Europe and changed the landscape beneath and around them. 140,000 years ago, the Saale Ice Age peaked, and when the ice melted away, what is now the Wadden Sea area appeared as a hilly landscape - not unlike what we know from eastern Denmark. There are not many hills left along the Wadden Sea today, yet the area is not completely flat - there are remnants of soft hills that can be seen as higher parts along the coast. These are known locally as geest. Around 11,500 years ago, the last ice age (Weichselian) ended and the ice only reached about 80 kilometres east of the Wadden Sea area. Rivers of meltwater emerged from the ice and travelled through the landscape, carrying sand and gravel towards the sea. The large amounts of gravel and sand formed a thick and even blanket that sloped westwards, turning the landscape into a flat plain.

The islands emerged

After this, the ice loosened its grip and the seas began to rise. By around 8,000 years ago, the water had risen so much that it had become what is now the North Sea. Since then, tides, wind and waves have shaped the landscape. The North Sea brought the sand from the great meltwater rivers back towards the coast, where it was deposited as sand flats. Over time, the sand flats reached a height where they were rarely flooded. This is how one of the characteristic landforms of the Wadden Sea emerged: the High Sands. The high sands were dry and gave plants room to grow. The plants caught blowing sand between their stems, laying the foundation for the first dunes and Wadden Sea islands.

Animals and plants

Every high tide, around 2 cubic kilometres of water wash through the depths of the Danish part of the Wadden Sea. The water brings large amounts of sand and clay into the lagoons between the islands and the mainland, where a small amount is deposited in the calm environment. The mudflats are home to large numbers of benthic animals such as mussels and snails, which filter water and clay particles in their search for food. In short, the fine particles pass through the animals and come out the other end as larger particles. Coarse particles are harder for waves and currents to move around, so wildlife has a role to play in adding material to the mudflats.

The role of humans

The lush marshlands attracted early humans who settled on the higher-lying geest, in some safety from storm surges. As an additional protection against the sea, the first dikes were built in the Tøndermarsken in the Middle Ages. Today, only the marshes around Ho Bugt and in Varde Ådal are not diked, depriving most of the marshlands of their natural development with annual flooding and inputs of material. As technological developments allowed for this, the human imprint on the landscape began in earnest. The channel through Grådyb near Esbjerg was dug deeper and the dams at Rømø and Sild were built. These are all examples of infrastructure that has affected the natural balances between decomposition and deposition in larger areas.

Fotos: Carsten Pedersen, RedStar, Svend Tougaard