Massive buildings protect the 750-kilometer-long coastline of Lower Saxony: The coastal residents have defied waves and storm surges for centuries with, among other things, meter-high dykes and groynes. What has proven to be efficient for coastal protection, however, offers little benefit for nature itself. On the contrary: some barriers even look like rigid foreign bodies in the northern German coastal landscape.
Scientists from the joint research project “Good Coast Lower Saxony” are now daring to rethink the land defense that has been tried and tested for years: They want to bring both sides, coastal protection and ecology, together in the future.
Coastal protection in harmony with nature
The researchers are looking for natural coastal protection elements that nature provides by itself – they call this ecosystem-based coastal protection. “What services do salt marshes in front of the dikes provide for dampening waves, and quantifiable? We already know that they are useful, but not exactly how much and to what extent,” says Torsten Schlurmann, head of the Ludwig Franzius Institute for Hydraulic engineering, estuary and coastal engineering at the University of Hanover. In the past, coastal protection was built into nature. In the future, it will be about building coastal protection with nature.
Schlurmann started rethinking in 2004 after the tsunami in the Indian Ocean. In Sri Lanka he saw entire coastal strips flooded – except for a small strip, where a naturally existing coral reef in front of the coast dampened the tsunami for the coast. “That was an eye opener for me personally: intact nature can do something in coastal protection,” the professor is convinced.
Several institutes from the three Universities of Lower Saxony, Oldenburg, Hanover and Braunschweig, have joined forces for the joint project “Good Coast”, which is being funded over five years by the Volkswagen Foundation with five million euros. “The key question we asked ourselves is: What is a good coast,” reports Schlurmann. What makes the coast worth living in, ecologically valuable, but also safe and economical at the same time?
Fight against flooding
The scientists see the rise in sea level as a central challenge – and a danger for the Wadden Sea, because dykes limit it in the south. “The only chance the Wadden Sea has is, it has to grow up over sediments – and faster than the sea level rises,” explains Oliver Zielinski from the University of Oldenburg, who is also working in the joint project. A part of “Gute Coast” is therefore examining how the mudflats could grow with the help of salt marshes that accumulate sediments.
The scientists want to align their research with actual needs. “The different perspectives, for example from a fisherman, from a mudflat guide or from vacationers, that you get, that is valuable knowledge that we can include,” says Zielinski. The quality of the knowledge gained with this “real laboratory approach”. Three areas around Spiekeroog, Neßmersiel and Butjadingen were selected as “real laboratories”.
In a sub-project, the researchers are working on the development of new grass seeds to improve dike strength. What you want to consider: Today’s seed mixtures, which are optimized for the maintenance of the dykes, offer little more than a handful of different grasses. “A win-win situation would be to use the seed mixtures to support biodiversity on dykes in order to increase the ecosystem performance while at the same time having the deepest and most resilient roots possible,” says Schlurmann.
The researchers want to test the new grass seeds on summer dykes and regularly check the density and depth of the roots. The objections of the coastal residents were also heard: “If the sheep even taste it, you checked it,” said Schlurmann, for example the question of the dike associations.
The neighbors in the Netherlands show how it could work. These are years ahead of ecosystem-based coastal protection, says Schlurmann. They do not want to tear down the dykes, emphasize the researchers from “Gute Coast” – but they are sure that they will not be able to do so in the future without relying more heavily on nature.