Ecology: Salt marsh contributions to coastal protection
22 October 2026
Salt marshes can survive extreme wave events with modest erosion but are likely to offer the best flood protection to coastlines that experience moderate storms, according to the results of experiments in a massive wave flume reported in Nature. Despite the apparent stability of underlying marshy ground during extreme storms, damage to plants in the soil is substantial and can reduce their ability to dissipate waves. The results could help identify where conserving and restoring salt marshes may contribute most effectively to coastal protection.
Flood protection strategies that focus on dissipating wave energy are becoming increasingly important in the face of rising sea levels and increased exposure to storms. Salt marshes can be a natural solution to dissipate wave energy due to their elevated beds and the roughness of the vegetation they host. However, how salt marshes behave during extreme wave events has not been thoroughly investigated.
Pim Willemsen and colleagues carried out a large-scale experiment to analyse the marsh’s response to extreme waves; they transported and installed 306 square metres of salt marsh and vegetation in the Delta Flume wave generator, one of the world’s largest wave flumes. After 21 hours of waves up to 2-metres tall interacting with the marsh and vegetation, the authors found that only 7 millimetres of the marsh’s surface has eroded. Vegetation reduced by 33% after the first wave run, from 831 grams per square metre to 558 grams per square metre. After 21 hours the above-ground biomass decreased to 20−25% of the initial biomass and stem length reduced by 47%. The vegetation was responsible for the most attenuation for small waves as opposed to larger waves. The authors extrapolated these results to a global scale using data on storm surges, coastal elevation, and salt-marsh distribution. Their analysis suggests that vegetation can reduce waves by more than 10%, and by up to 50% on lower-energy marsh coasts, which are those with waves up to one metre.
The authors suggest that restoring and conserving salt marshes at coasts that experience lower-energy storms could be a promising technique to mitigate against extreme storms. Even at coasts that experience high-energy storms, salt marshes may prove useful for wave attenuation, but mainly in tandem with engineered defences like seawalls.
- Article
- Open access
- Published: 21 October 2026
Willemsen, P.W.J.M., Mason, V.G., Zelst, V.v. et al. The contribution of salt marshes to wave attenuation during extreme storms. Nature (2026). https://doi.org/10.1038/s41586-026-11145-8
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