The flora of Cantabria is the result of three determining factors: the climate, the composition of the soil, directly dependent on the types of existing rocks, and the evolutionary history of the different plant formations.

From the point of view of its flora, Cantabria is located between two biogeographic realms. Most of the territory belongs to the Eurosiberian region, but the southern end is part of the Mediterranean region. This border situation has a direct effect on the characteristics of the plant landscape of the region, where Mediterranean and Atlantic species intermingle, enriching the botanical composition of the different existing ecosystems.

Origin of current vegetation

The vegetation of Cantabria is adapted to two types of substrate. On the one hand, there are limestone rocks, as in Peña Cabarga or Picos de Europa, with little soil development and a large amount of outcropping rocks, which have a very characteristic flora adapted to these types of soils, called calcareous flora. These are very similar throughout the region and are especially abundant in the eastern sector, where this type of substrate predominates. On the other hand, there are acidic rocks (such as sandstones, clays or siltstones), which supply few nutrients to the soil. This type of material harbors an acidophilic flora very characteristic of the high mountains of the Cantabrian Mountains which is, in general, dominant in the region.

The other determining factor of the composition of the current vegetation landscape is the evolutionary history of the different floristic communities present today. This evolution is due both to biogeographical causes and to the influence exerted by man over the centuries. The Quaternary glaciations, together with the interglacial periods, marked the evolution of the different phases of the flora of the region, which went through very cold periods, with tundra-type vegetation, and warmer periods, in which temperate deciduous hardwood forests spread throughout the territory. Three thousand years ago is generally considered to be the approximate date when the vegetation acquired similar characteristics to the present, that is, dominated by deciduous hardwood forests, accompanied by Mediterranean forest formations, with evergreen species and covering the territory from sea level to 1700 - 1900 meters, considered the ceiling of the wooded vegetation in Cantabria. Of this potential vegetation, only a small unaltered part survives today in the most inaccessible parts of the region. In the rest of the territory, human action has caused the degeneration of the forest, and the appearance of substitution stages, made up of heaths and scrublands, and pastures and meadows, the basis for livestock feeding.

The vegetation landscape can also be defined by its bioclimatic floors, which are distributed in a staggered manner with respect to altitude. Four bioclimatic floors or horizons can be differentiated in Cantabria:Rivas Martínez (1983). «Pisos bioclimáticos de España». Archived from the original on November 18, 2011. Accessed on August 30, 2007. the colline, the montane, the subalpine and the alpine, the latter restricted to the summits of the Picos de Europa.

Colline zone The colline level, which is distributed from approximately sea level to 500 – 600 meters above sea level, has a vegetation landscape dominated by the presence of mowing meadows, the basis of dairy cattle feeding, which have been implanted by man, replacing the old temperate deciduous forests that covered the entire territory. This area has been the most transformed by human development, as it is here that the majority of the population and a large part of the infrastructure and intensive exploitation is located, so its ecosystems show a significant degree of alteration.

The vegetation communities of these coastal territories include those typical of the littoral (beaches and dunes, cliffs, and marshes), hay meadows, mixed deciduous forests, holm oak groves, riverside forests and eucalyptus plantations.

Dunes

Coastal dunes are one of the most endangered ecosystems in Cantabria. Its species, all herbaceous, are exclusive to these ecosystems, so their disappearance would mean the irreversible loss of highly specialized plants.

In the area closest to the sea, where the grains of sand deposited by the tide are intercepted, slightly above the average high tide, the first band of pioneer dune vegetation begins to settle, represented in Cantabria mainly by northern couch grass (Elymus farctus), generally accompanied by prickly saltwort (Salsola kali), searockets (Cakile maritima) and arenaria (Honkenya pelopides).

Where there is no marine influence, the sand dunes rise and form strands in the inner part of the large beaches of Cantabria. A certain stabilization of the dune occurs in this growth zone, as a result of the settlement of vegetation that reduces its mobility, especially beachgrass (Ammophila arenaria) which, due to its wingspan and intricate root system, is the main fixative plant in this environment. Other characteristic species of this area are sea holly (Eryngium maritimun), carex (Carex arenaria) or sea spurge (Euphorbia paralias).

Further inland, in the more sheltered areas of the beach, the sandy substrate is fixed in extensive plains covered by less specialized vegetation, in which sandy species are mixed with other opportunistic ones. Meadows of Festuca rubra, Lolium perenne, Lagurus ovatus, Phlenum arenarium and Briza maxima are typical. There are also other species such as Medicago marina and M. littoralis, Linaria maritima, Dianthus monspessulanus and Otanthus maritimus.

Cantabria is home to the largest dune field in the Cantabrian Sea, the Liencres Dunes, declared a natural park by Decree 101/1986 of December 9, 1986. The main natural element that determined the creation of the Park is the dune system located on the right bank of the mouth of the Pas river.Government of Cantabria (2006). «Orden GAN/67/2006, de 21 de julio, por la que se acuerda la iniciación del proceso de elaboración y aprobación del Plan de Ordenación de los Recursos Naturales de las Dunas de Liencres, Estuario del Pas y Costa Quebrada.». Archived from the original on January 22, 2008. Accessed on January 17, 2008. The park is a true ecological jewel, due to the enormous development of its dunes and its acceptable degree of conservation, which is threatened by the urban development projects currently existing in its surroundings, which far exceed the carrying capacity of this valuable ecosystem. It was also included in the National Inventory of Points of Geological Interest of the Geological and Mining Institute of Spain (IGME).Linares Argüelles, Mariano; Pindado Uslé, Jesús; Aedo Pérez, Carlos. (1985). «Tomo III». Gran Enciclopedia de Cantabria (Santander: Editorial Cantabria, S. A.). .

Coastal flora

The cliff coasts of Cantabria, of vertical development and variable height, are home to communities adapted, as in the case of the dunes, to the proximity to the sea. These communities develop on two types of substrates: hard limestones, dominant on the surface in the region, and marl and sandstones, which are more brittle and have more developed soils.

The first vegetation belt, the one closest to the sea, is characterized by the presence of herbaceous species growing in the fissures of the rocks, such as sea fennel (Crithmum maritimum) or sea plantain (Plantago maritima) and, in more protected fissures, spleenworts (Asplenium marinum).

Moving towards the edges of the cliff, the vegetation becomes more abundant, also including Armenia maritima (Armenia maritima and A. pubigera ssp. depillata) and sea lavender (Limonium lanceolatum), to the east of the estuary of San Martín de la Arena, in Suances. The areas where it is not possible for upper vegetation to take root are colonized by lichens, such as Xantoria parietina or Verrucaria maura.

The emergence of more spread out areas where vegetation settles more easily makes possible the appearance of new species such as wild carrot (Daucus carota ssp. gummifer), Portuguese angelica (Angelica pachycarpa) or sweet alyssum (Lobularia maritima), accompanied by small meadows of grasses dominated by red fescue (Festuca rubra).

Finally, in elevated areas, quite far from the sea, there are thickets of Cornish heath (Erica vagans), genista (Genista occidentalis) and gorse (Ulex europaeus).

Estuaries and marshes

The marshes constitute one of the habitats of greatest scientific interest, since they possess the highest biodiversity of all the existing ecosystems in Cantabria. In Cantabria, the marsh communities are well developed in Santoña, Victoria and Joyel Marshes Natural Park«Ley 6/1992 de 27 de marzo (Head of State), por la que se declara Reserva Natural a las Marismas de Santoña y Noja.». BOE. 1992. Accessed on January 19, 2008. (broken link available in Internet Archive; see history, first version and last version). in the Rabia estuary, and in the two Tinas (Tinamayor and Tinamenor). As in the case of the dunes, their conservation is threatened by the urban development pressure in their surroundings.

These communities form a complex of floristic associations with a very diverse distribution, atomized and variable in space, responding mainly to the degree of salinity of the environment.

The marshes of Cantabria have, in the areas most flooded by sea water, meadows of Zostera marina and Zostera noltii, both species in danger of extinction on the European Atlantic coast. Near the lower tidal level, cordgrass (Spartina spp.) appears, followed by salicornia (Salicornia spp.) or limonium (Limonium vulgare). Finally, in the areas farther from the sea, with less influence of salt water (such as river mouths, banks of canals and ponds), there are rushes and reed beds of Juncus spp., common reed (Phragmites australis) and Scirpus spp.

Hay meadows

Beyond the strictly coastal area, the vegetation landscape is characterized by the dominance of intensively managed mowing meadows, in which forage gramineae such as Lolium perenne, Holcus lanatus, Anthoxanthum odoratum, etc. appear, intermingled with leguminous plants such as cloverslike Trifolium pratense or Trifolium repens. These meadows are the plant formation that occupy the largest area in the region, distributed in large spaces with very few trees on their margins and with hardly any hedges separating the farms.

Mixed deciduous forests Distributed in valleys and enclaves that are difficult to manage due to their excessive slope, there are few remains of the type of forest characteristic of this colline level, the mixed forest (deciduous multispecific). They are composed of a mixture of different species, among which the common oak (Quercus robur) dominates, accompanied by ash (Fraxinus excelsior), maple (Acer pseudoplatanus), birch (Betula celtiberica), linden (Tilia spp. ), chestnut (Castanea sativa) and a large number of tall shrubs such as common hazel (Corylus avellana), alder buckthorn (Rhamnus frangula), dogwood (Cornus sanguinea) or laurel (Laurus nobilis), interspersed with lianas and epiphytes, thickets and herbaceous plants. These forests, with a great floristic diversity in their undergrowth, used to occupy the best soils of the territory, so they have been massively displaced from their natural habitat to plant crops, constituting the most transformed forest mass and therefore the one of most interest for its restoration.

Holm oak forests