Location and General Description
The Pyrenees are situated between the Eurosiberian and the Mediterranean biogeographic regions of Europe. The mountain range extends in a west-east direction from the Atlantic Ocean to the Mediterranean Sea, covering 500 km2. The central axis of the Pyrenees is composed of ancient granite and slate more than two hundred million years old, flanked by Mesozoic (limestone, dolomite, and sandstone) and quaternary sedimentary rocks. The Alpine orogeny has shaped the complex Pyrenean landform. It consists of steep rocky slopes, spectacular canyons, karstic high plains, and high summits of more than 3,000 m (Aneto 3404 m, Posets 3,375 m, Vignemale 3,298 m). Evidence of Quaternary glaciation is everywhere, with stunning cirques and ice-smoothed, U-shaped valleys.
The Pyrenees are divided into three major bioclimatic sectors. The western portion is affected by the mild and humid Atlantic air streams, the central continental sector by colder and drier weather, and the eastern section by a Mediterranean influence, which brings warm summer drought. A Mediterranean transitional climate type predominates in the southern Pyrenean lower ranges, known as the "Prepyrenees".
The Pyrenees are characterized by a highly diverse altitudinal zoning of forest types, which becomes more evident in the southern Spanish half. Lower elevations and limestone/dolomite canyons have a Mediterranean vegetation type, where mixed evergreen (mainly Quercus ilex) and deciduous species (Quercus faginea, Q. pubescens, Tilia platiphyllos, Acer opalus) predominate. Cork oak (Quercus suber) and stone pine (Pinus pinea) form important forest stands in the siliceous substrates of the easternmost extreme, near the Mediterranean Sea. Medium elevations are characterized by deciduous mixed forest (Q. petraea, Q. pubescens; Fagus sylvatica mainly to the west) and pine forests of Scotch pine (Pinus sylvestris) and Mediterranean black pine (P. Salzmannii). Relic juniper woodlands (Juniperus thurifera), widely spread in Central Spain and North Africa, appear in few areas of the Northern Pyrenees. High mountain forests are mainly composed of mixed beech (Fagus sylvatica) and silver fir (Abies alba) stands, with mountain pine (Pinus uncinata) mainly found in more continental inner regions. Strictly alpine meadows occur above the timberline and host many endemic and relict species.
The Pyrenees is an interzonal mountain system (orobiome), in effect a "transition area" between Central and Mediterranean Europe. There remains a high degree of naturalness over large areas. About 3500 vascular plant species are recorded from the mountains, of which about 200 are endemic, such as Thalictrum macrocarpum, Androsace hirtella, Saxifraga hariotii, Hieracium compositum, Gentiana burseri, Globularia gracilis, and Galium caespitosum. There are two endemic genera representing relicts of subtropical origin: Borderea pyrenaica and B. chouardii from the central Pyrenees, and Xatardia scabra from the eastern Pyrenees. The genus Ramonda, which has one species endemic to the Pyrenees (R. myconae) and two species endemic to the Dinaric Mountains, should also be mentioned.
About 64 species of mammal inhabit the Pyrenees, including some endemic subspecies. Large carnivore populations have been reduced in size or fragmented into small remaining groups. The brown bear (Ursus arctos) population is composed of only a few individuals. Large herbivores are generally have wide distributions, with the exception of the Pyrenean endemic ibex subspecies (Capra pyrenaica pyrenaica). Unfortunately, this animal went extinct in early 2000.
About 120 breeding bird species have been identified, as well as an equal number of migratory species. A very highly endangered raptor is the lammergeier (Gypaetus barbatus), of which some forty pairs are still found in the Pyrenees. Other endangered species, more widely spread in Northern Europe, form isolated populations in certain mountain areas. These include the capercaillie (Tetrao urogallus) and the ptarmigan (Lagopus mutus).
Wilderness areas can still be found in certain valleys, canyons, and high slopes of the Pyrenees. Some species of special concern have critically low populations and are susceptible to extirpation in these mountains.
Types and Severity of Threats
Intensive logging operations, ski runs, winter tourism resorts, road construction, and power stations/dams threaten the survival of some of the best preserved forest habitat in Western Europe. Current human activity in the Pyrenees does not bode well for the forests’ endemic plant species, large mammals, and bird populations. In fact, forest fragmentation and road construction are leading to the likely extinction of the Spanish brown bear populations. Air pollution related to power stations has already provoked major problems for important forest areas in the eastern Pyrenees.
Justification of Ecoregion Delineation
This ecoregion is equivalent to the DMEER unit of the same name, and the boundaries are primarily a result of that process. It includes a complex of vegetation types in and around the Pyrenees, including areas of lowland to altimontane beech and mixed beech forests, sub-Mediterranean downy oak forests, sub- and oro-Mediterranean pine forests, subalpine and oro-Mediterranean vegetation, alpine Mediterranean vegetation (Bohn et al. 2000).
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Prepared by: Pedro Regato
Reviewed by: Leann Trowbridge