The Maritime-Terrestrial National Park of the Atlantic Islands of Galicia comprises the archipelagos of Cíes, Ons, Sálvora and Cortegada, which are found around five kilometres off the Galician coast. Composed of shallow seas, karstic sea cliffs and islands with sandy dunes, springs and poor mineral soils, the Site is of great scenic beauty and supports a wealth of plants and animals. In the archipelagos’ diverse wetland habitats 34 endemic plant species can be found. Supporting nine internationally protected species of whale and five internationally protected turtle species, the Site is important for marine species as well as terrestrial species and birds. The Site’s 51 sea caves are important for significant communities of marine invertebrates and algae as well as important populations of bats. More than 20,000 waterbirds, many of them protected, are regularly recorded at the Site. The yellow-legged gull (Larus michahellis) is notably abundant with more than 1% of the population counted at the Site during their reproductive period. The Site is part of a long-term research collaboration between scientists, National Park managers and institutions to understand the ecological processes underlying the Site’s many ecosystem services. During the summer months many tourists visit the National Park. The main threats are invasive species, overfishing and pollution with household effluents.