Tropical forests in the Iberian Peninsula?

We are in the 21st century after Jesus Christ. The entire Iberian Peninsula is occupied by vegetation with a temperate climate. All of it? No!. Some patches of forest with tropical characteristics are still resistant to the invasive climate...

Although today the Iberian Peninsula is at a temperate latitude, its geological history bears witness to a tropical past. Millions of years ago, during the Eocene period, this region was much closer to the equator and enjoyed a tropical climate, and therefore tropical forests.

However, despite its current location, the Iberian Peninsula is home to forests that, across distances, resemble those of subtropical or tropical regions.

The main characteristics of tropical and subtropical forests are that they are very diverse and complex ecosystems found in warm regions with high rainfall.

In the Iberian Peninsula, microclimates occur on a one-off basis that can present similar characteristics, being located in protected and humid areas, such as deep canyons or areas of higher altitude. Some of the species found in these forests may have affinities with tropical or subtropical plants.

An example of these forests could be the laurel forests that are located in several enclaves in the north of the peninsular. El Laurel (Laurus nobilis) is a species that generally appears together with other species in biotopes that are favorable to it, such as oaks, cork oaks, oaks, linden trees or ash trees, it can even appear in some Mediterranean vegetation, generally associated with protected valleys or valleys, which conserve moisture, mainly in the north of Catalonia.

However, in some areas, the laurel appears to form pure masses, with dense and diverse vegetation, and with an abundance of lianas. This laurisilva is a type of humid, evergreen forest that is largely composed of broad-leaved species. This type of forest is typical of areas with cool and humid climatic conditions, and is usually found in areas of moderate altitude.

Among the species that accompany these laurels, strawberry trees stand out (Arbutus unedo), the alligustre (Ligustrum vulgare), the ruscus (Ruscus aculeatus) and some lianoids such as sarsaparilla (Smilax aspera), ivy (Hedera helix) black walnut (Tammus communis) species that, according to several authors, could form part of paleosubtropical floristic elements. In this sense, these formations can constitute relict formations, which have survived to this day under certain appropriate conditions.

A forest with an organization similar to the laurel formations, would be the Alzinares Litorale, which extend mainly across northern Catalonia and in areas of the Balearic Islands. This is a forest where the main species is alzina (Quercus ilex ilex), and under the tree specimens there is a stratum 2 to 5 meters high in which some species stand out, such as durillo (Viburnum tinus), the Aladdierno (Rhamnus alaternus), the strawberry tree (Arbutus unedo),... together with some female climbers such as honeysuckle (Lonicera sp), and again sarsaparilla, ivy..., These are species that also have wide, lauroid-type leaves, which could suggest, as in the previous case, an adaptation to subtropical conditions, which have been able to come to this day under certain favorable conditions.

Towards the south of the peninsula, we also find some curious strongholds of this type of vegetation. One of these most interesting strongholds would correspond to the loreras. Loreras are called the formations of the species parrot, which is one of the common names of the species Prunus lusitanica. This name refers to its resemblance to a bay leaf.

This species is considered a relic of laurisilva forests that were of great importance in the Iberian Peninsula during the tertiary period, which, like other species, has survived the Quaternary glaciations, in some protected canyons.

Their preferred environment corresponds to small shelters with humid and temperate microclimates, with mild winters and frequent fogs also in summer. The distribution of loreras mainly corresponds to the western peninsular, associated with a mild, Atlantic climate, although it also appears in some areas further east (La Rioja, Navarra, Catalonia).

The largest and best developed formations of this species are located in some mountain ranges of Extremadura and Castilla La Mancha, mainly in the mountains of Guadalupe, the Villuercas and the Montes de Toledo. The structure of these formations would be that of a dense forest, in which several small trees with wide and elongated leaves are located, such as the one itself Prunus lusitanica, together with species already mentioned in other formations such as strawberry trees (Arbutus unedo), Durillo (Viburnus tinus), Holly (Ilex aquifolium), heathers (Erica sp.), together with vines such as vines (Vitis sylvestris), ivy (Hedera helix), The Black Walnut (Tammus communis) and also several ferns.

If we compare with the species found in the Canarian laurisilva (Viburnum rigidum, Arbutus canariensis, Ilex canariensis, Erica sp. Hedera canariensis) we can observe the similarity of both formations.

Finally, further south, we can still find some formations that respond to the same structure. These are the so-called”Canutes”, which are located in the coastal mountains of Cádiz and Malaga. In these joints, humid and cool conditions have been maintained, protected from the Quaternary glaciations, which have allowed some of the species from previous periods to be preserved. Some of the species of ferns and mosses found in these joints are the same as those found in the Canary Islands or the Equator.

Among the species that form these joints, in the tree stratum we can find both Andalusian Quejigo (Quercus canariensis) such as Laurel (Laurus nobilis). In the shrub stratum, broad-leaved species such as durillo (Viburnus tinus), arraclán (Frangula alnus), holly (Ilex aquifolium), olivilla (Phyllerea latifolia), male whale (Daphne laureola), and the presence of leaf litter stands out in particular (Rhododendro ponticum).

Finally, we also found a high number of lianas such as ivy (Hedera helix)), sarsaparilla (Smilax aspera), the blonde (Rubia peregrina), the black walnut (Tammus communnis) and honeysuckle (Lonicera sp), as well as a high number of ferns and mosses, creating a dense forest with a distinctly subtropical appearance.

Therefore, as mentioned at the beginning, although the subtropical vegetation that existed in the Iberian Peninsula has been mostly replaced by temperate vegetation, some formations have survived in certain redoubts, with specimens of wide and long laurioid leaves, both of the arboreal type (laurel, alzina, parrot) and shrubs (strawberry tree, durillo...) and in which a high number of vines and vines (ivy, sarsaparilla, walnut...) as well as ferns and mosses stand out. All these characteristics determine formations with a clear analogy with subtropical vegetation, and which in any case, represent a singularity in the vegetation of the peninsula, which is worth knowing and protecting.