One common prediction for the future is global warming will create stronger storms. What does this mean when a storm hits the shore? It depends what’s on the coast. Researchers from China and the Netherlands have examined how various factors affect marsh vegetation. Dr Zhenchang Zhu, the lead author of the study, said: “Our paper looks at the variation of plant traits associated with flood defence value of coastal ecosystems under environmental changes, which is an essential element to be considered during the design and implementation of nature-based flood defence.”
The study, which should be of use to policymakers as well as coastal ecologists and engineers, examines how a change in species alters coastal defence.
The study found that increasing salinity tended to cause a shift in species. Species with tall shoots and high flexural stiffness gave way to shorter species with more flexible stems. Dr Zhu said: “Generally speaking, stiffer plants are more effective in reducing wave energy than flexible plants, provided that the other settings (stem height, diameter, shoot density etc.) are the same. But stiffer plants may break more easily than flexible plants that can avoid the stress by bending. So there should be a balance.”
Changes in species could have positive or negative effects, depending on the species in a locality. However, once the properties of local species are known, then local effects can be predicted. Dr Zhu said: “One major benefit of this research is that it can feed numerical models that assess the spatial and temporal variation of wave attenuation by coastal vegetation, in a more accurate way.”
The team conclude that it is vital to understand the response of community composition to climate change and human disturbances when using nature-based flood protection by coastal vegetation as an adaptive response to global change. They hope their work will mitigate some of the effects of increasingly extreme weather.
Zhu, Z., Yang, Z., & Bouma, T. J. (2019). Biomechanical properties of marsh vegetation in space and time: effects of salinity, inundation and seasonality. Annals of Botany. https://doi.org/10.1093/aob/mcz063