Location and General Description
The Southwest Iberian Mediterranean sclerophyllous and mixed forests Ecoregion extends all along the low elevations, valleys, plains, and Atlantic coastal strip of the southwestern part of the Iberian Peninsula. Land surface is mainly part of three major river basins, the transboundary Spanish-Portuguese basins, the Guadiana basin, the Tajo basin, and the Spanish Guadalquivir basin.
Generally speaking, the ecoregion is composed of very old crystalline substrates (granite, schist, quartzite, and marble). Mesozoic and Quaternary sedimentary rocks (sand, sandstone, conglomerate, and limestone) occur infrequently in certain coastal areas. Climatically, the ecoregion experiences very hot and dry summers and relatively mild and humid winters. Annual average temperatures range from 13-19º C, and the minimum average temperature of the coldest month ranges from 1-10º C. The ecoregion is influenced by cold offshore currents, which tend to moderate the temperatures and increase air humidity. Annual rainfall ranges from 450-900 mm.
The ecoregion’s forests are mainly composed of evergreen broadleaf canopy species. Cork oak (Quercus suber) forest extends from the coast to low and medium altitudes on siliceous substrates in the western half of the Mediterranean region (Portugal, Spain, France, Italy, and northern Morocco). These Iberian cork oak forests are the most extensive of the whole Mediterranean region. Cork oak forests mainly grow at a humid and warm bioclimate type, with annual rainfall ranges of 600-800 mm and with no frost appearance, from the shore to about 1,500 m. Cork oak forests are characterized by a very rich evergreen and subtropical-like mixing of small trees and high shrubs. Tree species include Laurus nobilis, Arbutus unedo, Erica arborea, Ilex aquifolium, Phillyrea latifolia, P. Angustifolia, Viburnum tinus, Cytisus villosus, and Myrtus communis, with a very representative liana-layer of Lonicera periclymenum hispanica, Smilax aspera, Rubia peregrina var. longifolia, and Hedera helix.
Holm oak (Quercus ilex) and holly oak (Quercus coccifera) forests are common. Holm oak is an euryecious species, which can withstand wide temperature and rainfall variations and any type of substrate. These once covered extensive areas with deep and humid soils, which have since been transformed into agricultural land. Mixed cork oak and holm oak sylvopastoral woodlands appear frequently throughout the ecoregion. Holly oak generally constitutes dense maquis and small forest stands in a humid and warm climate on any type of substrate. The holly oak formations are characterized by a dense evergreen tree and high shrub layer of Myrtus communis, Arbutus unedo, Chamaerops humilis, Pistacia lentiscus, Erica arborea, and Phillyrea latifolia, and also including many liana species.
Wild olive (Olea europaea and O. maroccana) and carob (Ceratonia siliqua) woodlands and maquis were once widely spread all along the fertile, deep soils of the warmest dry coastal and inland plains. This has since been intensively transformed into agricultural land. Only few remnants maintain the natural structure of this forest type. Human impact, mainly from grazing, fires, and firewood collection, has transformed the majority of the existing wild olive and carob plant communities into secondary dense shrubs or "maquis" or into agro-forestry landscapes composed of scattered trees on grasslands or crops. Furthermore, wild olive and carob have been widely domesticated in order to produce olive oil or food and fodder, respectively. A large number of high shrubs or small trees characterize these woodlands and maquis. These include the small palm tree Chamaerops humilis, Pistacia lentiscus, Phillyrea latifolia, P. angustifolia, and Myrtus communis. Associated lianas are Clematis cirrhosa, C. flammula, Smilax aspera, Tamus communis, Rubia peregrina, and Bryonia dioica. Herbaceous species include Arisarum vulgare, Vinca difformis, Allium triquetrum, and Ballota hispanica and frequently appear within the dense and shady tree layer. Small shrub species such as Lavandula dentata, Lycium intricatum, Calicotome villosa, Osyris lanceolata, Jasminum fruticans, and Rhamnus oleoides characterize open woodlands and more degraded shrublands.
The endemic shrub, Securineia tinctorea, which has a distributional range almost completely restricted to this river basin, together with several shrub and tree species (Tamarix canariensis, T. africana, Salix alba, and Populus alba), characterize the typical riparian woods that are well adapted to periodical flooding.
The coastal stone pine woodlands (Pinus pinea), associated with sand dunes, are very valuable ecosystems from both socio-economic (sustainable management of pine nut collection is an important income-generating activity for rural economies) and conservation point of view (mainly soil stabilization and biodiversity preservation). For example, the largest Portuguese population of Chamaelo chamaelon is found in the Monte Gordo Nature Reserve, close to the western margin of the mouth of the Guadiana.
So far, there are no quantified data regarding the endemic vascular plant species of the ecoregion. Undoubtedly, the rate of endemism is very high, as many endemic plants are associated with the ecoregion. The exceptional number of continental (pools, marshy lands, volcanic small lakes, and supersaline lagoons), and coastal wetlands (dotted around the river stream network and along the southern Portuguese coastal line) makes the ecoregion an outstanding freshwater hotspot. It is very surprising to find certain relict habitats related to the northern European freshwater ecosystems, such as sphagnum peat bogs, and birch (Betula pendula) copses.
Evergreen oak woodlands (Quercus ilex, Q. suber), extensive and highly diverse shrublands with a large number of endemic species (i.e. species from the genera Cistus, Lavandula, Genista, Thymus, Erica, etc), and varied semi-natural grasslands, form a complex landscape pattern. This is very valuable in terms of biodiversity conservation, soil protection, and hydrological stability. Certain mountain areas, such as Monchique in the southwestern extreme of the Algarve and Montes de Toledo in the northern part of the river basin, support unique and very endangered plant species and communities. These include the Tertiary relicts, Prunus lusitanica and Rhododendron ponticum baeticum, and communities dominated by Quercus canariensis and Arbutus unedo. These rarities are extremely valuable from the conservation point of view.
The ecoregion also represent an important refuge for certain mammals, such as otter (Lutra lutra), and for an important number of reptiles (i.e. Emys orbicularis, Mauremis caspica, Chamaelo chamaelon), as well as wintering (i.e. Anas strepera, Netta rufina) and nesting (Ardea purpurea, Nycticorax nycticorax, Circus aeruginosus) bird species.
The ecoregion’s river mouths and coastal lagoons are among the most important (i.e. Doñana NP) and best wintering site for many Anatidae species, flamingos, and a large number of migratory birds that depend on these natural habitats for their periodical migrations.
The ecoregion boasts more than 220 breeding vertebrates, about twenty percent of which are raptors including Elanus caeruleus, Circaetus gallicus, Aegypius monachus, and Gyps fulvus. The woodlands constitute important wintering enclaves for thousands of cranes (Grus grus), and also breeding areas for hundreds of white storks (Ciconia ciconia) and the endangered black stork (Ciconia nigra). The traditional southwestern Iberian sylvopastoral landscapes are also fundamental for the preservation of some of the most endangered species in Europe, including the Iberian lynx (Lynx pardinus), the imperial eagle (Aquila heliaca), and the great bustard (Otis tarda).
Major land-use changes induced by governmental policies are responsible for the past and on-going land degradation and habitat fragmentation in the ecoregion. The socio-political instability of the first half of the 20th century provoked land clearance of vast woodlands, which were transformed into marginal lands unable to sustain agriculture. This was supported by governmental subsidiary policies, known as the "Wheat Campaign" in Portugal. By 1950 it was officially recognized in Portugal and Spain that soil degradation had reached serious proportions in the south. Rural abandonment and emigration to urban areas, and the subsequent agricultural decline, was followed by a desertification process. This led the governmental subsidies to promote productive reforestation programs, mainly based in non-native conifer and eucalyptus species. Large scale planting for timber and pulpwood transformed large semi-natural areas of marginal lands and woodlands into artificial plantations, and new irrigation and marshlands drainage plans destroyed significant marshlands and woodlands in the main river basin. The short-term high productivity of the eucalyptus plantations (Portugal has the second largest world plantation, with more than 300,000 hectares) is obtained at the expense of severe environmental degradation threatening the long-term preservation and potential productivity of the natural resources.
The surface area covered by eucalyptus has almost reached its peak and is not currently expanding (it is even decreasing in Southern Spain). However, the environmental incentives put in place by the European Union under the CAP reform, to convert marginal agricultural land into more or less natural forests, do not favor the survival and restoration of the original forest ecosystems. Ironically, after a total EU investment of 1.27 billion ECU between 1993-97 for environmental forestry measures, of which one third went to Spain, important natural habitats of forest, scrub, and grassland are still being cleared or destroyed. Soil erosion is increasing, biodiversity is decreasing, and the viability of the small and fragmented populations of highly threatened species like the Iberian lynx is becoming uncertain. Inadequate reforestation in terms of methods and species, under CAP subsidies in the Guadiana Valley Natural Park, cover more than 16,000 hectares -about 13% of the territory- provoking high erosion rates. According to Vale Formoso Experimental Erosion Centre, the oldest European research center on desertification located within the Park boundaries, erosion is estimated at 40 tons of soil loss per hectare/year, while under natural scrubs and pasture lands it becomes almost insignificant.
Types and Severity of Threats
Human impact remains high in this ecoregion. Degradation is mainly a result of agricultural intensification and large irrigation plans including extensive greenhouse crops on coastal land, inadequate forestry programs promoted by European Union subsidies, climate change impact on overexploited sylvopastoral woodlands, coastal tourism and urbanization, dam construction, road building, and inadequate and overly intense hunting practices.
Justification of Ecoregion Delineation
This ecoregion is equivalent to the DMEER (2000) unit of the same name. It is composed of the cork oak forests, thermo-Mediterranean cork oak forests, thermo-Mediterranean Quercus ilex subsp. rotifundifolia forests, along with small areas of coastal vegetation, flood-plain vegetation, and Iberian supra- and meso-Mediterranean Quercus forests (Bohn et al. 2000).
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Prepared by: Pedro Regato
Reviewed by: In process