Ecological consequences of sea level rise and flood protection strategies in shallow coastal systems: A quick-scan barcoding approach

Abstract

Shallow coastal ecosystems have high ecological value and contribute to flood protection. Their stability is, however, sensitive to the amount and rate of future sea level rise (SLR), their ability to trap sediment which allows them to grow with rising sea level, and human response to SLR. So far, studies have focused on assessing SLR impacts using resource-intensive tools. Here, we present an approach for a first-order assessment and easily accessible ‘barcode’ visualization to rapidly assess potential impacts of both SLR and adaptation strategies on coastal ecosystems in a spatially explicit way. Our approach relates habitat types (ecotopes) to water level, morphology and salinity, allowing users to determine shifts in spatial arrangements of ecological zones under different SLR rates and strategies. We illustrate this approach for a transect in the Dutch Wadden Sea. We find that beyond a critical rate of SLR, major changes in ecotope distribution are projected to occur as this part of the Wadden Sea starts to drown due to insufficient sediment import. Even larger impacts arise from adaptation strategies. Closing the barrier islands will turn the Wadden Sea into a freshwater lake-system with the absence of intertidal areas, infilling of channels and bank erosion. A strategy that allows for inland migration of the shoreline, results in a deep tidal basin with large subtidal habitats, and a shifted intertidal zone. Our case study shows that the barcoding approach provides a rapid, quantitative and spatially explicit overview of the potential implications for coastal ecosystems under different SLR scenarios, adaptation strategies and time horizons. This can then be used to screen adaptation strategies before going into a more comprehensive analysis. The barcode visualization allows for easy dissemination of potential ecological impacts to a broad community.