Abstract
BackgroundSalt marshes lie between many human communities and the coast and have been presumed to protect these communities from coastal hazards by providing important ecosystem services. However, previous characterizations of these ecosystem services have typically been based on a small number of historical studies, and the consistency and extent to which marshes provide these services has not been investigated. Here, we review the current evidence for the specific processes of wave attenuation, shoreline stabilization and floodwater attenuation to determine if and under what conditions salt marshes offer these coastal protection services.Methodology/Principal FindingsWe conducted a thorough search and synthesis of the literature with reference to these processes. Seventy-five publications met our selection criteria, and we conducted meta-analyses for publications with sufficient data available for quantitative analysis. We found that combined across all studies (n = 7), salt marsh vegetation had a significant positive effect on wave attenuation as measured by reductions in wave height per unit distance across marsh vegetation. Salt marsh vegetation also had a significant positive effect on shoreline stabilization as measured by accretion, lateral erosion reduction, and marsh surface elevation change (n = 30). Salt marsh characteristics that were positively correlated to both wave attenuation and shoreline stabilization were vegetation density, biomass production, and marsh size. Although we could not find studies quantitatively evaluating floodwater attenuation within salt marshes, there are several studies noting the negative effects of wetland alteration on water quantity regulation within coastal areas.Conclusions/SignificanceOur results show that salt marshes have value for coastal hazard mitigation and climate change adaptation. Because we do not yet fully understand the magnitude of this value, we propose that decision makers employ natural systems to maximize the benefits and ecosystem services provided by salt marshes and exercise caution when making decisions that erode these services.
Highlights
Salt marshes provide humans many vital benefits known as ‘ecosystem services’ and one of the most important may be their role as buffers in protecting coastlines
In order to ascertain the utility of salt marsh ecosystem service provisioning for coastal planners and managers and to inform decision making related to ecosystem-based adaptation, we provide the most thorough synthesis of the protective benefits of salt marshes to date
We address three specific ecosystem services associated with coastal protection: wave attenuation, shoreline stabilization, and floodwater attenuation
Summary
Salt marshes provide humans many vital benefits known as ‘ecosystem services’ and one of the most important may be their role as buffers in protecting coastlines. Our coasts face a variety of natural hazards including storms, hurricanes, and tsunamis. These hazards are natural processes that have always affected the coastal zone, the impacts and associated costs of these hazards to humans have increased as the amount and value of coastal infrastructure have grown and continue to grow. Interest in natural or ecosystem-based coastal protection strongly increased after two recent natural disasters: the Indian Ocean tsunami and hurricane Katrina. Salt marshes lie between many human communities and the coast and have been presumed to protect these communities from coastal hazards by providing important ecosystem services. We review the current evidence for the specific processes of wave attenuation, shoreline stabilization and floodwater attenuation to determine if and under what conditions salt marshes offer these coastal protection services
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