The relative contribution (%) of the predictor variables to the BRT models over the regional scale.

The predictor variables, by relevance were mean grain size (MGS), sediment shear strength (SS), mean sea surface temperature (sst), and chlorophyll a (chla). The predictor variables with the highest contribution described the recorded observations of the dominant beach species (same as in Table 1). Beach species included in the final model: Bathyporeia pelagica, Donax trunculus, Eurydice affinis, Eurydic pulchra, Pontocrates arenarius, Scolelepis squamata, Sphaeroma rugicauda, Talorchestia brito and Talitrus saltator.