Coastal grassland vegetation records from São Miguel Island (Azores) and the south-western coast of mainland Portugal

Most records consolidate previously documented occurrences from national repositories, but here they are re-validated through standardised, plot-based, georeferenced surveys that harmonise taxonomy and metadata. Crucially, this release constitutes the first coordinated, standardised inventory of coastal grassland vascular plants spanning the Azores and the south-western mainland of Portugal, enabling direct cross-regional comparisons. In addition to several within-plot distributional updates, we document multiple introduced and invasive taxa, most notably <i>Carpobrotus edulis</i> and <i>Oxalis pes-caprae</i>, that are known to reshape coastal communities. As expected for Atlantic coastal grasslands, the flora is dominated by Asteraceae, Poaceae, Fabaceae and Brassicaceae, providing a baseline for long-term monitoring and management across both archipelagic and continental shores.