When are Nature Based Solutions true solutions?

Marine ecologist Brenda Walles studies various Nature Based Solutions for infrastructural problems. “During my PhD I looked at the possibilities and limitations of oyster reefs, as a brake for the waves on a coastline. Now, as principal investigator at the department of Estuarine and Delta Systems in Yerseke, I broaden that research to the question what Nature Based Solutions can and cannot do under influence of climate change and how we can influence their resilience.”

 Oysters breaking the waves
During her PhD-research at Wageningen Marine Research in Yerseke, Walles found out that oysters can effectively break the waves, but only when the waters are shallow enough. “In tidal waters, that means that there is a limited time, depending on the difference between high and low tide, where oysters take the beating of the waves. With a tidal difference of more than three meters in the Dutch Delta, there is a very limited time that oyster reefs effectively break the waves, protecting a small portion of tidal flats. In the Gulf of Mexico, however, where the tides vary considerably less, these reefs can be a good option to protect vulnerable coastlines.”

 Differences between plants
Not only oyster reefs can dampen the force of rolling waves. Plants on salt marshes can do that too. “But there it makes a big difference how these plants grow. A particular species of coastal plant, like Spartina anglica, may display different growth forms across Europe. As a result, it may provide important ecosystem services as a Nature-Based Solution in certain areas but be less effective in delivering these benefits elsewhere. In experiments with different plants, and with different genetic lines within one plant species, I intend to find out whether these Nature-Based solutions become more robust or more vulnerable under the influence of climate change. I hope to identify their limitations under different circumstances and the impact of climate change.”

 Adding sediment to mudflats
“A second track in my research evolves around specific measures we sometimes need to take to preserve nature or coastal defense. To preserve foraging habitat for birds, we sometimes add huge amounts of coarse sediments to mudflats. However, this has a large impact on the benthic community. It takes a while before worms, bivalves and other organisms recover from the blow. Furthermore, these added sediments differ from natural tidal flats, and may act differently to the rising temperatures we see under influence of climate change. In recent years we have seen considerable dying of bivalves during (marine) heatwaves. By looking at the specific effects of either coarse or muddy sediments, I hope to find out how we can mitigate the effects of heatwaves in future tidal flat nourishments in our Delta.”

A significant part of this research will be done in the context of the Delta Climate Center