The variation in the altitude of the region, which in a short distance ranges from sea level to 2,600 meters in the mountains, leads to a great deal of diversity in vegetation and a large number of biomes. Cantabria has vegetation typical of the Atlantic side of the Iberian Peninsula. It is characterized by forests of leafy deciduous trees such as oak and European beech. Nevertheless, human intervention dating back to ancient times has favored the creation of pastures, allowing the existence of large areas of grassland and prairies suitable for grazing cattle. These grasslands are mingled with plantations of eucalyptus and native oak. The southern part of Cantabria, including the comarca of Campoo the fringes of the Castilian plateau, is characterized by the transition to drier vegetation. Another diversifying factor which contributes to local variation within the region is the Mediterranean ecotone, giving rise to species unique to the region, such as the holm oak and arbutus trees, which are found in poor limestone soils with little moisture.
In Cantabria there are several zones of plant life:
The coastal strip, including sandy dunes with minimal vegetation. Adjacent to these are steep cliffs with plants unique to that type of terrain.
The maritime region, near the coast and including altitudes up to 500 metres. Originally it had mixed deciduous forests containing ash, linden, bay laurel, hazel, maple, oak, poplar, birch, holm oak, and others. The riparian parts were filled with forests of alder and willow. Today these native forests have almost completely disappeared, leaving only reserves in area of poor arability. In their place there are grasslands which are quite productive in the temperate climate and which sustain the economy of rural Cantabria. Next to these are very large monoculture plantations of eucalyptus for paper production, of disastrous ecological consequences to the biodiversity and climate of the region.
During the last two decades of the 20th century, and due mainly to European agricultural policies (CAP), many farmers substituted forestry for livestock farming, so as to avoid unemployment and poverty. This provoked a surge of eucalyptus – see eucalyptus article on Spanish Wikipedia – plantations (and to a less extent of pines) which often hid the illegal destruction of native forests, just as the spread of livestock farming had done in the past by the endemic conversion of forest into prairie. These acts have been laxly controlled by the local councils or the central governments, in a process that clearly follows the saying: “Pan para hoy, hambre para mañana” (which translates as ‘Bread for today, hunger for tomorrow’; i.e., “short-term gain, long-term pain”).
The plantation of pines has given way in the last decades to that of eucalyptus because this non-indigenous species has no natural attacker within the European ecosystem (while pines are highly vulnerable to the pine processionary). Both in relative and absolute terms the use of woods for forestry has increased in Cantabria, and is now almost 70% of all woods in the region.
The foothills, from 500 to 1,100 metres altitude are colonized by monoculture forests of oak (Quercus robur and Quercus petraea) on the sunnier slopes. In more shaded areas and especially from about 800 metres there are forests of European beech which are the main food source in winter for many animal species.
The subalpine plane, in this high country, the plant life is composed of birch, scrub, and grasses which are especially important for the economy because during the summer they serve as pasture for grazing cattle and horses.
Along with these characteristics it would also be necessary to mention peculiarities of the comarca of Liébana, which has a microclimate very similar to the Mediterranean, allowing to grow cork oaks, vines and olives, and which is still very well conserved from human activity. The other remarkable comarca is Campoo, in southern Cantabria, with its Pyrenean oak.