(This text was kindly contributed on our request by Dr. Hans-Ulrich Rösner, WWF Germany, regarding the German experience with embankments in tidal flats.)
Dr. Hans-Ulrich Rösner, WWF Germany:
First and foremost, I would like to emphasize that I do not wish to comment on activities in Korea, as I cannot adequately assess the local situation from afar. However, I can offer some insights into how we would evaluate similar measures in the context of the German-Dutch-Danish Wadden Sea.
The structures shown in the images are known as Lahnungen (sea embankments), which were historically used on a large scale in the Wadden Sea to calm tidal currents and facilitate land reclamation. By reducing the flow of water, these structures allow sediment to accumulate more rapidly, enabling the formation – or accelerated formation – of saltmarshes, which could later be embanked by dykes. Fortunately, the construction of such embankments has been prohibited in the Wadden Sea for several decades. However, even today, Lahnungen are still built or maintained directly in front of dykes – not for the purpose of land reclamation anymore, but to promote the development of a saltmarsh or ‘foreshore’ that serves to dampen wave energy and thereby protect the dyke from erosion.
The photograph shows such a case in the Wadden Sea. It also illustrates that, despite the presence of Lahnungen, the hydrodynamic conditions at that location do not, under real-world conditions, permit the natural development of saltmarshes.
It is worth noting that the structures depicted in the Korean context differ significantly from those traditionally used in the Wadden Sea. In Korea, the Lahnungen appear to be filled with stones, whereas in the Wadden Sea they are typically filled with brushwood. This method is more ecologically appropriate for the Wadden Sea, given the absence of a stony coastline in the region.
Importantly, the construction or maintenance of Lahnungen at a greater distance from the dyke is usually no longer permitted in the Wadden Sea, as in these more seaward areas such structures no longer serve a meaningful function for coastal defence, thus nature conservation has priority.
From a conservation perspective, I would generally advise against the artificial creation of salt marshes in the Wadden Sea at the expense of intertidal mudflats. The primary conservation objective for the Wadden Sea is to allow natural processes to proceed as far as possible in an undisturbed way. Accordingly, it is not appropriate to place a higher value on saltmarshes than on mudflats and to create them artificially. Natural dynamics in the Wadden Sea result in the natural formation of salt marshes in some areas and their erosion in others, giving way to mudflats. This ever-changing landscape is a key aspect of the Wadden Sea’s Outstanding Universal Value (OUV) and forms the foundation for its recognition as a UNESCO World Heritage Site.
With regards to birdlife, a large-scale transformation of mudflats into salt marshes could reduce available feeding grounds for many species. Given that food resources in the Wadden Sea might almost fully be utilized by waders and waterfowl, such habitat loss could potentially have adverse effects on bird populations.
