If sea levels rise by more than a metre, many coastal marshes will be submerged by seawater, even those that continue to accrete sediment.
Coastal marshes are not just passive casualties of rising sea levels but respond dynamically to changes in inundation, vegetation and sedimentation. Modelling these dynamic feedbacks reveals that the loss of coastal marshes to rising seas is not inevitable but depends on site characteristics as well as on the rate and magnitude of sea-level rise.
A team led by Matthew Kirwan of the US Geological Survey, Maryland, USA, modelled the feedback mechanisms that control how coastal marshes respond to rising seas1. This analysis offers a more dynamic insight into the risk of coastal marsh inundation than conventional analyses, which traditionally assume stasis or are based on historical responses.
If sea-level rise is restricted to around 30 cm, with minimal ice-sheet contributions, over the coming century, many marshes will be able to keep pace with rising seas and maintain their position, found the authors. However, a sea-level rise of more than a metre would permanently submerge most coastal marshes, including many that will continue to grow by accretion.
References
Kirwan, M. L. et al. Limits on the adaptability of coastal marshes to rising sea level. Geophys. Res. Lett. 37, L23401 (2010).
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Brown, A. Coastal casualties. Nature Clim Change (2010). https://doi.org/10.1038/nclimate1025
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DOI: https://doi.org/10.1038/nclimate1025
