Giving land back to the sea
Giving land back to the sea: it sounds scary, but results in a safer, more biodiverse coast
image: Elevation map of Dutch Flanders. It clearly shows that the polders surrounded by dikes are low-lying (green and blue colours). The dikes are high (dark orange). The areas outside the dikes such as the Drowned Land of Saeftinghe are higher than the average sea level (orange). The low (light green) Hedwige polder lies just south-east of this area. In 50 years, the polder will also be much higher, because it will be raised by the sea. Source: Algemeen Hoogtebestand Nederland. view more
Credit: Algemeen Hoogtebestand Nederland
Biodiversity
The task of restoring nature and combating biodiversity loss is the reason why the Hedwige and Prosper polder had to be de-poldered. Land reclamation for agriculture and industry, as well as deepening of the channel, has put the tidal nature in the Western Scheldt under severe pressure. As a result, the areas of the submerged mudflats suitable for foraging birds and fish have declined sharply. Salt marshes, land outside the dikes with rare plants and animals, are also under severe pressure. Now mudflats and salt marshes can once again grow in the 465 hectares of the former Hedwige and Prosper polder - a major step in restoring nature and biodiversity.
Daily flooded and raised above sea level
In the coming years, most of the area will consist of mudflats, unvegetated soft mud full of bottom-dwelling animals. Gradually, the mudflats will overgrow over the coming decades. Silt will stay behind between the vegetation after each flood, causing the area to rise faster. Thus, slowly but surely, creating an area higher than the average sea level.
Nature itself builds a safe coast
Van Belzen: “The beauty of this project is the fact that we are letting nature itself build a safe coastal defence. One that even grows with rising sea levels.” Due to climate change, we expect an increase in extreme weather. Dikes without vegetated foreshores must be able to withstand huge waves and water pressure. But salt marshes soften the waves during a storm, so that dikes behind the salt marshes do not have to be raised as high, as sea levels rise.
Salt marshes store a lot of CO2
“There is another big advantage,” says van Belzen. “The vegetated salt marshes also capture large amounts of CO2 in the soil, much more than forests. This is of great importance. If some of the man-made CO2 can be reabsorbed by nature, it can help minimize climate change.”