Coastal dunes are fragile ecosystems that provide essential services and support diverse habitats, whose preservation is critical for sustaining these benefits. These dunes exhibit a characteristic cross-shore zonation in vegetation, shaped by physical gradients primarily influenced by proximity to the shoreline. The interaction between vegetation, topography, and aeolian sediment transport drives dune formation and evolution. As a result, the existence and composition of these habitat zones offer valuable insights into the dunes' morphological evolution and vulnerability. Many plant species in these environments have evolved specialized traits to adapt to, and sometimes benefit from, challenges such as sand burial, strong winds, low nutrient availability, and salt spray. Therefore, it is essential to monitor both the morphological state of coastal dunes and the composition of their vegetation cover to detect potential perturbations. This database includes observations (counts) of plant composition across multiple profiles along the Ria Formosa Barrier Island System in southern Portugal, applying the standard line transect sampling. The data is the result of the counting of plant species or sand (in case plant species were not found) using the standard line transect sampling method. The method is explained in the reference Costas et al. (2023) and consists of counting species that appear every 50cm along a line of 25m parallel to the shoreline. The position of these lines is relative to a cross-shore profile, which defines the events. The number of lines perpendicular to a profile depend on the observed changes in the community and the morphology of the coastal dune under analysis.