Modelling saltmarsh spatial evolution at high resolution from 1948 to 2100 (Beaussais's Bay, France)
Résumé
Saltmarshes are boundary sea-land-air ecosystems which are globally threatened despite the plethora of ecosystem services they provide. Their evolution is spatially complex and multifactorial, influenced mostly by ecological and physical drivers such as tidal range, wave energy, hydrologic components and climatic conditions. Saltmarshes can respond positively to climate change due to their adaptiveness especially in areas provided with high tidal energy. While the conditions and determinants of marsh evolution are known locally, the spatial mapping of such processes across time is strongly expected.It is hereby proposed to study the interactions of the spatial evolution of Beaussais' Bay saltmarsh (France) from 1948 to 2013 by means of ocean-climate data. Time series of the saltmarsh spatial response, based on five high resolution aerial photographs, were explained by a multiple linear regression on continuous temperature, precipitation and mean sea level data. The model significantly explained the average horizontal accretion of the marsh platform by local warming and rising sea-level (Pearson's correlation coefficient r=0.63, RMSE=5.22). The increase in temperature explains best the model (R2=0.88), while sea-level and precipitation are secondary predictors (R2=0.16 and R2=0.11, respectively). The model enabled fine-resolution mapping to be predicted based on both IPCC ocean-climate scenarios and historical trends of the marsh surface up to 2100. The findings confirm the trends observed so far, enhancing the importance of saltmarsh conservation as a coastal protection. Spatial modelling of the marsh platform evolution constitutes therefore an intuitive framework and accessible communication tool for coastal planners.
