From marshes to coastlines: A metric for local and national scale identification of high-value habitat for coastal protection

Saltmarshes and mudflats provide many valuable services to society, including coastal protection. Previous studies have established the nonlinearity of wave attenuation with habitat width, and variation with vegetation type. However, spatial variation in the level of coastal protection has not been quantified on a national scale. Spatial distribution and fine (50 m) scale structure of saltmarsh habitat at a national scale was combined with calculations of wave fetch at a 200 m scale. Effective wave exposure as a result of wave attenuation over habitat was calculated for areas of coastline within 5 km of habitat areas. Effective wave exposure was combined with data layers on building and farmland locations in order to assess relative protection provision. A metric of coastal protection was calculated for the entire coastline of England and Wales, based on the proximity of human infrastructure and farmland. In scaling existing local and regional data on coastal protection to a national level, we may examine how coastal protection varies regionally and provide a criterion for coastal ecosystem managers to select marshes critical for conservation. Our index shows greatest protection of human infrastructure by marshes in the east and south of the UK, where saltmarshes are on relatively open coastlines with nearby built-up areas and agriculture.