Can salt marshes keep up with sea level rise?

This summer we conduct field surveys across the Wadden Sea, where we measure sediment accretion or erosion at fixed positions, along with vegetation surveys. This way we can link patterns in sedimentation rates to vegetation dynamics.

Pioneer salt marsh consisting of (among others) cordgrass and Salicornia species. By Fee Smulders

The salt marshes at the mainland coast of Friesland and Groningen are semi-natural as they are accompanied by wave-reducing dams and drainage networks. Because of these past and current management practices in combination with an abundance of fine sediment near the coast, this area has high accretion rates of about 8 - 20 mm per year. However, the salt marshes on the barrier islands grow at an average rate of 1 - 4 mm per year, making them much more vulnerable to drowning at current sea level rise level of 2 - 3 mm per year. We cannot be sure to say when or how these salt marshes may drown in the future as this depends on sediment dynamics within the whole Wadden Sea area. But we know that salt marsh vegetation can be quite resilient once settled.

Picture of one of our permanent plots, with the sedimentation-erosion bar (SEB) which we use to measure sedimentation and erosion with a 1.5 mm accuracy in front, and the 2 by 2 m plot in which we assess vegetation cover and diversity in the back. Note the goose marks as proof of the important habitat and food function of salt marshes! By F. Smulders.

We were joined by Gert Elbertsen of Vroege Vogels for a radio report (in Dutch) of our work. You can listen to the radio fragment via the link below (it starts after 31.30 minutes).