Review of methods for quantifying the benefits of coastal wetlands in absorbing and buffering extreme weather event impacts on coastal infrastructure

Coastal wetlands reduce extreme weather event impacts on coastlines globally. As climate change is expected to increase the frequency and intensity of these events, understanding how wetlands absorb and buffer extreme weather events is essential for promoting their conservation and restoration as a climate adaptation strategy. This systematic literature review examines methods used in previous research to quantify impacts of extreme weather events on the protective benefit of coastal wetlands (mangroves and tidal marshes) and the infrastructure they protect. Drawing from 129 studies, we categorise reported impacts on wetlands as: mechanical damage (33%), sediment dynamics (8%), and water properties (0.8%). Reductions in extreme weather event impacts by wetlands were categorised as infrastructure damage (23%), hydrodynamic forcing (39%), or social impacts (7%). On average, extreme weather events damaged 65% of mangroves and 8% tidal marshes. Coastal wetlands reduced wave height by 46% ± 27% and coastal flooding by 47% ± 15%, reducing infrastructure damage by up to 60%. Methodologies used to quantify impacts included: spatial models (25%), field-based approaches (28%), change analyses (19%), linear models (10%), non-linear regression (7.8%), economic valuation (4%), index development (4%), and Bayesian network models (2.3%). Choosing the best method depends on impact types, data availability, funding, and scale, with trade-offs between accuracy, cost-effectiveness, and scope. We discuss how these trade-offs may inform future investigations and the implications of robust methodologies for insuring properties and nature. Future research should assess variation in impacts along environmental gradients and explore how wetlands regulate socio-cultural consequences of extreme weather events.