Vegetation as a Protection Barrier

The role of wetland vegetation in protecting shorelines from wave-generated erosion and inundation has recently come into question from small-scale experiments. Contrary to this finding, we find overwhelming support that mangrove and salt marsh vegetation afford protection from erosion and storm surge. In biophysical models, field tests, and natural experiments, the presence of wetlands reduces property damage, human deaths, and wave heights in proportion to the distance of wetland traversed by waves. In addition to these direct effects on waves, coastal wetland vegetation modifies shorelines in ways (e.g. accretion of peat and plant production) that increase shoreline integrity (e.g. reduce erosion) over longer timescales and thus may help buffer against the threat of increased sea-level rise.   Although we find coastal wetland vegetation to be an effective shoreline buffer, wetlands cannot protect shorelines in all locations or scenarios. Larger wetlands will afford more protection than smaller wetlands, and large shore-breaking waves, such as tsunamis, may not be reduced by even large wetlands. Combining some man-made structures with natural wetlands may increase the overall effective coastal protection. Historically, these man made structures, such as jetties, have created major drawbacks, such as disrupting coastal sediment transport. However, our research shows that new, nature-mimicking structures, such as oyster domes, can be used in combination with salt marshes to synergistically reduce wave stress, protect shorelines and restore critical fishery habitat. This new approach of integrating man-made and natural structures generates both complementary and synergistic interactions to help secure and protect shorelines under siege from both wave and inundation threats.