Background The Bay of Santander is the largest estuary on the north coast of Spain extending over 41 675 ha. Due to the influence of the city of Santander and its metropolitan area, nearly half the region’s population is situated around the bay area. Despite its relative shallowness, the bay serves as the city’s main seaport and has consequently undergone dramatic changes. A significant part of the original marsh was drained to build industrial areas, highways and meadows, for instance, and one runway of Parayas Airport extends into the bay. Today, 38% of the estuary is still a natural environment of great ecological value. However, continual pressures threaten biodiversity and ecosystem services in the bay. Objectives The main LIFE Anillo Verde project objective is to contribute to nature conservation in seven municipalities of the Bay of Santander, by improving and restoring ecosystems and habitats, and enabling the population recovery of species. It will also aim to halt the loss of biodiversity, to sustain ecosystem services, and to restore, insofar as possible, estuarine and bay ecosystems by creating a green and blue infrastructure: the ‘Green Belt of Bay of Santander’. Further to these aims, the project will: Design the ‘Green Belt Bay of Santander’ as a permanent and long-term sustainable infrastructure, and develop appropriate management tools and funding; Restore characteristic ecosystems of the bay, including the removal of invasive alien species; Improve the connectivity of natural areas of the bay from ecological and sustainable mobility perspectives; Raise public awareness of the natural, cultural, and social values of the bay through the green belt , and promote the territory as a sustainable tourist destination; and Foster the expansion of the bay’s green belt, through land stewardship agreements with owners of public and private properties. Expected results: The project’s expected results are: The creation of a green and blue infrastructure, the ‘Green Belt of the Bay of Santander’, and the design of basic tools for its sustainable long-term management; Reduced territorial fragmentation through improved ecological connectivity within and between nature reserves, and by promoting sustainable mobility through trails and other paths to improve the public use of natural areas; An evaluation of ecosystem services in the bay and the increase in these achieved after the implementation of the project; The enhancement and restoration of 95 ha of degraded habitats (e.g. coastal wetlands, inland wetlands, relict oaks, and islands); The removal of 150 ha of invasive fauna and flora (e.g. Cortaderia selloana, Baccharis halimifolia and Reynoutria japonica); A reduction in the number of fires by up to 80% around the Bay of Santander (helped by the removal of C. selloana); The removal of illegal landfill and the prevention of uncontrolled waste dumping within all reserves; Increased environmental awareness among the local population on the green belt, and the use of green and blue infrastructure to provide jobs, ecosystem services and to improve quality of life. Activities will include guided tours, schools involvement, and voluntary work; The creation of a business lobby to support the green belt in the medium and long term; The implementation of at least one ecotourism initiative leveraging the green belt as a tourist resource; and Regarding the improvement of ecosystem services, improved quality of soils to increase grassland quality and meat prices from green belt areas, increased capture of CO2, and improved ecological status of the islands.