The importance for biodiversity and conservation in the SAC Complexo Ons - O Grove (ES1140004) is endorsed by the identification of a large set of habitats and species of community interest in the Master Plan of the Natura 2000 Network of Galicia (Ramil-Rego et al., 2012), approved by Decree 37/2014, which is the basic planning and network management instrument for Natura 2000 Spaces in Galicia. The Plan establishes a set of objectives and management measures for the natural spaces that are included in its scope of application, in order to ensure a favorable state of conservation of the types of natural habitats and of the species of community interest of the CD. 92/43/CEE and DC 2009/147/CE.
According to the diagnostic information of the Master Plan of the Natura 2000 Network of Galicia, the SAC Complexo Ons - O Grove (ES1140004) houses in its territory some natural values of great interest from the point of view of conservation, being possible to identify up to a total of 35 different types of habitat of community interest (Annex I of CD 92/43/EEC), of which 6 are considered priority (1150*, 2130*, 2150*, 6220*, 7210*, 91E0*) . In other words, within this space, which represents 2% of the Natura 2000 Network of Galicia, there is representation of 49% of the total types of habitat of community interest identified for Galicia and 33% of the priority types in the Autonomous Community. (Ramil-Rego et al. 2008a, b). This important set of habitat types, with special attention to the variety of coastal habitats present, contribute to the improvement of the connectivity of natural and semi-natural habitats, functioning as essential link points for the migration and genetic exchange of wild species. .
The eminently coastal nature of this space means that the largest group of habitats is that of Coastal habitats and halophytic vegetation with 13 different types identified (100% of all those identified in Galicia within this group), of which one is a priority (1150*). The group of Maritime and Continental Dunes is also well represented, since it has 7 habitats that also account for 100% of the habitats of this group present in Galicia, of which 2 are priority (2130*, 2150*). Therefore, the variety, contact and continuity of the coastal habitats with the dune habitats is remarkable, since in both groups the SAC Complexo Ons - O Grove (ES1140004) houses representations of all the types identified in Galicia, which highlights the important role that this space plays from the point of view of the conservation of biodiversity and natural heritage, as well as for the coherence of the Natura 2000 Network of Galicia, since these ecosystems are highly fragile and vulnerable to threats identified in this project.
However, consulting the environmental mapping of the Natura 2000 Network Master Plan, made publicly available by DXPN, makes it possible to verify that the types of habitat that occupy the largest area are community interest rate 4030 with 473.77 ha ( 6% of the SAC), type 2130* with 174.27 ha (2% of the SAC), type 8230 with 145.18 ha (2% of the SAC) and type 1230 with 164.22 ha (2% of the SAC). In other words, the habitat types with the greatest surface representation of the Complexo Ons - O Grove SAC (ES1140004) make up an extensive complex of high conservation value and community interest, located in contact with the transition formed by types 2130* and 4030, addressed by LIFE INSULAR in this document. The dune ecosystems of the type 2130* contact, following a horizontal axis, with the cliffs of the type 1230, while vertically catenally they contact the coastal thickets of the type 4030, which in turn are also in contact with the type 1230. These 2 types of habitat (1230, 4030), in turn, include important representations of siliceous rocks of type 8230.
For all of the above, the representation of coastal and insular habitats of the SAC Complexo Ons – O Grove (ES1140004), together with those of other Atlantic archipelagos in the Natura 2000 Network of Galicia (Cíes, Sálvora), also included in LIFE INSULAR, are among the best in the entire Iberian NW.
In terms of flora and fauna, the SAC Complexo Ons - O Grove (ES1140004) has a high number of species of interest for conservation, with a total of more than 100 species with some category of European, state or regional protection, in its majority corresponding to birds, being a place that houses various colonies of migratory birds. A total of 16 taxa are included in Annex II of CD 92/43/EEC, which represents 43% of the total number of species of community interest identified in the Natura 2000 areas of the Galician coastal area.
Among the different groups of species of interest, the presence of 13 species of flora with some category of European, national or regional protection stands out, with notable examples of aquatic species (such as Lithothamnion corallioides or Phymatholithon calcareum, considered Vulnerable) and terrestrial species (such as Rumex rupestris or Cytisus insularis, considered Endangered).
The diversity of invertebrates in the SAC Complexo Ons - O Grove (ES1140004) is remarkable, especially terrestrial taxa, but also aquatic, which find in this space an ideal habitat for their populations, since it is possible to identify a total of 8 species of this group, which represents 67% of the invertebrate taxa of interest for the conservation of Natura 2000 spaces in the coastal area of Galicia. It is possible to cite examples cataloged as Vulnerable in the lists of threatened species, such as Echinus esculentus or Eunicella verrucosa.
The herpete community is considered highly diversified, among which the presence of the priority species Caretta caretta* and the species of community interest Discoglossus galganoi and Chalcides bedriagai should be noted. Likewise, the presence of various aquatic mammals has been detected in the waters of the archipelago, among which 2 species from Annex II of CD 92/43/EEC stand out, the common porpoise (Phocoena phocoena) and the bottlenose dolphin (Tursiops truncatus).
However, the importance of the Complexo Ons – O Grove SAC (ES1140004) for the conservation of bird species lies in the fact that within it it is possible to identify a variety of 70 taxa, of which 12 are included in the Annex I of CD 2009/147EC, such as the European Guillemot (Uria aalge) or the Dartford Warbler (Sylvia undata). Specifically, the Ons archipelago is home to more than 50 species of nesting birds, being one of those with the greatest specific richness in the entire southern Galician Atlantic coast. The most abundant populations are those of the Yellow-legged Gull (Larus cachinnans) and the Shag (Phalacrocorax aristotelis), finding here one of the largest colonies for this species.