When humans create the conditions, nature responds impressively fast. The Marker Wadden, an archipelago in the Markermeer, is powerful evidence. Initiated by Natuurmonumenten and Rijkswaterstaat, the nature islands were created from sand, clay and silt. Witteveen+Bos was involved in the design, construction and nature development of the first islands. We also played an important role in the accompanying research into developments on the islands.
The Markermeer Lake is located between the provinces of Flevoland and North Holland and measures 700 km2. On the upper side, the Lelystad-Enkhuizen dyke provides the separation from the IJsselmeer. The Markermeer is increasingly facing biodiversity decline.
The decline of the ecosystem in the Markermeer is the reason for the construction of the Marker Wadden. The Markermeer is a relatively shallow, wind-sensitive lake. The bottom is covered by a thick silt bed that is strongly stirred up thereby disrupting the life of plants, insect larvae, crustaceans and shellfish. Combined with decreased water nutrient richness, biodiversity is declining.
The Marker Wadden project was launched in 2016 to restore nature in the lake. The contract to create an initial series of islands was awarded by Rijkswaterstaat to the consortium comprising Boskalis, Arcadis, Vista landscape architects and Witteveen+Bos.
The islands are created from sediment (sand, clay and peat), surrounded by sandy edges and protected from waves by a large sand body between two stone abutments. The recessed areas around the islands and the lee created by the islands ensure floating silt is captured. This aims to reduce the silt problem and create clearer water in which plants and all associated fauna can grow and biodiversity improves.
Witteveen+Bos played several roles in the project. During the design phase, geotechnical engineers worked on behalf of Boskalis to design the two stone abutments for the large sand body protecting the islands. During the design phase, our ecologists worked on the design of the islands and created a plan for the intended wildlife development. During and after the realisation phase, our ecologists were responsible for developing marsh vegetation on the islands on behalf of Boskalis. And finally, our ecologists and remote sensing experts collaborated on the accompanying scientific research programme KIMA, which examined all developments on and around the islands for five years. More on this below.
Immediately after the first islands emerged, nature started to develop spontaneously and rapidly. Within a few weeks, as many as 2/3 of the Western European population of sand martins arrived at the Marker Wadden to feast on the many dancing midges that developed in the shallow water. Marcel Klinge: “The fact that these birds found that out so quickly and came flying in en masse from a great distance never ceases to amaze me!”
The task for Witteveen+Bos was to initiate a development of reed marsh as soon as possible after construction of the islands and stop the development of willow. This was a massive challenge, which our colleague Koen Princen took up with boundless energy and creativity: “Sowing reeds with a hovercraft, planting reed canes with volunteers, reducing goose feeding of the reeds with clever exclosures, flooding the islands during the period when the wind brings in willow fluff: these are just some of the many creative solutions that have been applied. That was wonderful, educational and effective!”