Boundaries

This ecoregion is located in the northeastern Iberian Peninsula. The boundaries stretch from the Segura basin in the south to the Ter basin in the north, encompassing the entire drainage basin of the Ebro River. The river basins drain the Mediterranean Sea and are bounded by a ring of highlands, including the Pyrenees and Cantabrian ranges to the north-northwest, the Iberian Range and Serriana de Cuenca to the west-southwest, the Catalan Coastal range in the east, and the northern edge of the Baetic Range in the south.

Topography

The topography is variable, ranging from the cliffs and dunes of the coastal lowlands and plains of the Ebro Depression to the plateaus and peaks of the Catalan Coastal Range, Iberian Range, Cantabrian Mountains, and Pyrenees. Elevations increase from sea level to more than 3400 m at Pico de Aneto in the Pyrenees (Hijmans et al. 2004). The ecoregion’s geomorphology is linked to the Alpine orogeny when the Iberian plate was subducted under the European plate, forming the Pyrenees and the Ebro basin. The Ebro was later landlocked by the Pyrenees, Catalan Coastal Range, and Iberian Range, resulting in an endorheic basin that filled with alluvial, fluvial, and lacustrine sediments. During the Miocene it opened to the Mediterranean Sea (Gibbons & Moreno 2003).

Freshwater habitats

The Ebro River is the largest Iberian river flowing into the Mediterranean Sea. Major tributaries include the Aragon, Gállego, Cinca-Segre, Oja, Iregua, Jalon, Huerva, and Guadalope. Rising in the Cantabrian Mountains, the Ebro flows 920 km to the southeast before reaching the Mediterranean Sea near Amposta. In the upper basin the river flows through meanders and canyons at a high velocity. Further downstream it meanders at slower speeds along the plain before flowing through more canyons in the lower basin (Sabater et al. 2009). The Ebro’s flow is highest from October to March in the upper basin, and downstream is high in May due to snowmelt in the Pyrenees. Groundwater inputs contribute to smooth the flow regime, although it is heavily regulated by dams in the Ebro and its major tributaries (Sabater et al. 2009). After crossing the Catalan Coastal Range the river empties into the Mediterranean Sea at the Ebro Delta, which is a large wetland with valuable biodiversity. It has a number of freshwater upwellings, brackish and saline lagoons, salt marshes, and coastal sandy areas. However, more than half of the delta surface is now devoted to rice cultivation, resulting in a general reduction in salinity and an increase in eutrophication, also favoring the dominance of freshwater invasive species, especially fish.

Stretching 500 km, the Júcar is the next longest river in the ecoregion. Rising in the Montes Universales, it cuts a path through the Meseta Central between the Iberian Range to the east and the Sierra de Altomira to the west, flowing south and then east before emptying into the Mediterranean Sea near Cullera. Tributaries include the Cabriel, Grande, and Magre. Important wetlands in the basin include the l’Albufera de Valencia (Sabater et al. 2009).

The Ter is the northernmost river in the catchment. Rising at 2500 m asl in the Pyrenees, it travels 209 km before reaching the Mediterranean Sea. Tributaries include the Freser, Gurri, Major, and Onyar. Snowmelt in the Pyrenees results in higher flow during spring. Like other Mediterranean rivers in Spain, the Ter’s hydrology is irregular due to variable conditions created by the Mediterranean climate, as well as anthropogenic influences. For example, the three reservoirs Sau, Susqueda, and El Pastoral regulate the flow and water quality in the lower part of the river (Sabater et al. 2009). One of the largest lakes in Spain, Estany de Banyoles, is located in the Ter basin. It is of tectonic and karstic origin, and is fed mainly by groundwater inputs.

Terrestrial habitats

This ecoregion encompasses a variety of terrestrial ecoregions, including the Northeastern Spain and Southern France Mediterranean forests [PA1215] along the coast; Iberian sclerophyllous and semi-deciduous forests [PA1209] throughout the central and southern part of the ecoregion; Iberian conifer forests [PA1208] at higher elevations in the Iberian Range; Northwest Iberian montane forests [PA1216] in the northern Iberian Range; Cantabrian mixed forests [PA0406]; and Pyrenees conifer and mixed forests [PA0433] (WWF 2001). The Iberian conifer forests have exceptional plant endemism, particularly on the Massifs of Gudar and Javalambre (WWF & IUCN 1994). Notable species include Salzmann pine (Pinus nigra subsp. salzmannii), Scots pine (P. sylvestris), maritime pine (P. pinaster), and Spanish juniper (Juniperus thurifera). Other continental species include mixed evergreen species like holm oak (Quercus ilex) and cork oak (Q. suber), as well as deciduous broadleaf species like Lusitanean oak (Q. faginea). There is also wild olive (Olea europaea) and carob (Ceratonia siliqua) woodlands and maquis. The Ebro basin has a number of saline swamps that are characterized by halophytic species such as Suaeda fruticosa, Microcnemum coralloides, Aizoon hispanicus, Arthrocnemum glaucum, and Limonium ovalifolium (WWF 2001). Species like the common dogwood (Cornus sanguinea) and false brome (Brachypodium sylvaticum) are found in both the headwaters and corridor of the Ebro River (Sabater et al. 2009).

Description of endemic fishes

More than half of the species in the ecoregion are endemic to the Iberian Peninsula. Of these, six are strictly endemic to Eastern Iberia, including the Ebro barbel (Luciobarbus graellsii), loina (Parachondrostoma arrigonis), madrija (P. turiense), Valencia chub (Squalius valentinus), Catalonian barbel (Barbus haasi), and samaruc (Valencia hispanica). Those restricted to two ecoregions include the Ebro nase (P. miegii), Iberian gudgeon (Gobio lozanoi), and Mediterranean barbel (B. meridionalis), also in the Cantabric Coast-Languedoc ecoregion [403]; lamprehuela (Cobitis calderoni), also in Western Iberia [412]; and Valencia barbel (Luciobarbus guiraonis) and fartet (Aphanius iberus), also in Southern Iberia [413].  The samaruc and fartet are present in a few wetland areas along the Mediterranean coast, but have declined due to the introduction of the eastern mosquitofish (Gambusia holbrooki) that competes for the same habitats (Sabater et al. 2009).

Other noteworthy fishes

The ecoregion contains threatened species like the loina (Parachondrostoma arrigonis) and samaruc (Valencia hispanica), which are Critically Endangered; and the fartet (Aphanius iberus), lamprehuela (Cobitus calderoni), and madrija (P. turiense), which are Endangered according to the IUCN Red List (IUCN 2009).

Ecological phenomena

Migratory fish such as the European eel (Anguilla anguilla), allis shad (Alosa alosa), twaite shad (A. fallax), sea lamprey (Petromyzon marinus), and Atlantic sturgeon (Acipenser sturio) were all once common along the Ebro, but have declined considerably due to the construction of dams (Nicola et al. 1996). In the case of the Atlantic sturgeon it was once common on the Ebro River and was also found on the Turia and Júcar rivers, but has not been recorded since 1970 (Almaça & Elvira 2000).

Justification for delineation

Southern European ecoregions were delineated based on a bottom-up approach employing both published and unpublished field data and expert assessment (Abell et al. 2008; Doadrio 2001). Within the Iberian Peninsula the northern and southern regions were geographically well-differentiated during all of the Cenozoic period. In the north three main endorreic lakes were present during the Miocene period. At the end of Pliocene the uplifting of the Iberian Peninsula resulted in two of them draining the Atlantic slope and one draining the Mediterranean slope (Lopéz-Martínez 1989; De la Peña 1995). This resulted in very different freshwater fish fauna between the Atlantic and Mediterranean sides of the Iberian Peninsula (Doadrio and Carmona 2003). There are also important ecological differences between these two regions. The Ibero-Mediterranean ecoregion (Eastern Iberia) is composed of limestone formations from sea deposits. The rivers are temporary and characterized by water scarcity during the summer and flooding events during autumn. The Ibero-Atlantic (Western Iberia [412]) occurs in the old craton of Europe and is composed of rocks that are silica-rich. Here, the rivers are more plentiful and more permanent because of Atlantic winds.

Level of taxonomic exploration

Good