Background Sand dune ecosystems across Europe are facing threats and pressures from environmental and human factors – especially tourism and recreational activities in coastal areas. This project targets 10 Natura 2000 sites on the Cantabrian coast in the Atlantic bioregion of northern Spain. They contain important priority sand dune habitats, including fixed coastal dunes with herbaceous vegetation, shifting dunes along the shoreline with Ammophila arenaria and embryonic shifting dunes. These are facing the same general threats as other European sand dune areas, putting characteristic species of beach-dune systems at risk. At the same time, the Priority Action Framework for the Natura 2000 Network in Spain has identified a general lack of information about the conservation status of habitat types and species in the Atlantic bioregion of Spain as a priority challenge for conservation action in Spain. Objectives The LIFE+ARCOS project aims to improve the conservation status of the targeted Cantabrian coastal sand dunes. It specifically aims to restore coastal sand dune habitat within 10 Natura 2000 sites. It seeks thus to address some of the conservation priorities identified in the Priority Action Framework for Natura 2000 in Spain The project will draft and implement action plans to restore sand dune habitats across the 10 sites. Actions include the removal of invasive trees and plants and the protection of dune habitats from human disturbance. The team will plant native grass species to restore the natural dynamics of dune ecosystems. To guarantee the long-term conservation of the crucial native grasses, the project will conserve the seeds of over 25 such plant species. It will develop protocols for plant cultures, which it will share with related ex-situ conservation projects. It will also develop germination protocols for several of the most threatened species and publish these on the relevant European database. The project will deliver a monitoring plan for the conservation status of the restored sites. This will aim to be applicable to the other dune systems in northern Spain and, with only few modifications, to all the dune habitats in the Atlantic bioregion. Expected results: Action plans for restoration of the selected dune systems; Elimination of at least 250 Pinus trees from the dune system of Barayo; Elimination of invasive alien plants from around 120 ha of dune systems in repeated eradication campaigns; Protection of dune systems against human disturbance by placing 5 000 m of wooden walkways and rope fences; Planting of more than 500 000 plants of European beach grass (Ammophila arenaria) and sand-couch grass (Elymus farctus) to restore natural dune ecosystem dynamics; Restoration of at least 50 ha of Fixed coastal dunes with herbaceous vegetation; Restoration of at least 65 ha of Shifting dunes along the shoreline with Ammophila arenaria and Embryonic shifting dunes; Conservation of germplasm (seeds) of at least 28 native plant species to ensure their availability in restoration actions; Definition of plant culture protocols for at least 10 species that will be incorporated into the parallel ex-situ conservation project, 'Phoenix'; Development of germination protocols for at least 15 rare or threatened species and publication of obtained results in the online database of the European Native Seed Conservation Network (ENSCONET);and Organisation of courses, meeting and events on dune restoration.