A natural mountain environment of outstanding quality.
The heritage value of the natural domain of Mont-Perdu cirques and canyons stems from a favorable conjonction of exceptional elements that fall within the province of geology, climatology and biology. The wealth of its landscapes comes from a peculiar geological arrangement which allows the observation of thrust fault layers formed by the Pyrenean "surrection". These layers determined the existence, in the middle part of the Pyrenees, of a dominating relief, which plays an important part in the climatic regimes. Such oreography has set up distinct areas clearly characterized by the climatic confrontation of the influence of the Atlantic to the North and the West, and the influence of the Mediterranean to the South-East.
The distribution of milieus, that of living species, the essentials of biological activity are regulated by the effects of these influences. That is why this domain is perfectly representative of a net of actions and reactions between the mineral world, the atmosphere, the biosphere ... and man, actions and reactions that built the Pyrenean mountain. For oreography and climate have actually favored communications and strong traditions of exchange established between neighboring human collectivities on both slopes over the years.
Yet, if the use of altitude dates back to the tertiary era, we must point out that it is some spectacular concave shapes stemming from alterations of quaternary erosion characteristic of limestone - cirques and canyons - that hold the visitor's attention best. So, "the boundless geological poem" that Franz Schrader sensed proceeds from two episodes distinct in time, a lengthy erection followed by an active erosion.
Animal and plant population stemming from the oro-climatic history of the cirques and canyons is outstandingly rich. Pyrenean flora has 3,500 species, 5% of which are endemic i.e. peculiar to the range, it is a remarkable proportion, probably higher here if we relate it to the dimension of the site. These species take advantage of the favorable nature of calcareous soil.
Let us take the example of the Añisclo canyon which is a rather original and priviledged space of life, a "biotope". an almost isolated world in some way. It shelters in particular the following endemic species: Ramondia Pyrenaica, the evergreenand the long-leafed snapdragon, a species that is strictly confined to the canyon. Its wildest fault scarps, close to fields and shrubby steppes, shelter the bearded vulture and other rare species.
Many other very different milieus, such as the forestry areas arranged in layered zones and vegetation strata, for a long time the shelter of ibex, the upper-forestry sites with their herbaceous strata, the cliffs, the windy steppes, the masses of fallen rocks, the extreme milieus harbor abundant animal and plant life which is admirably appropriate to the rigorous conditions proper to the mountain - a calcareous mountain with numerous meteorological effects. We could hold up as examples endemic plants that have for centuries, clung on to unsteady scree-covered slopes, such as "vesce argentée" and "dioscorée des Pyrénées", or the Pyrenean Lizard, and endemic reptile that lives through the seasons in the lapiaz situated above 2,000 metres (6,560 ft).
The fresh water milieu itself reveals the unexpected: a species that was so far unknown, was discovered by Spanish specialists: Euprocte (Rana Pyrenaica), a brown frog that populates mountain torrents as far as the under-alpine domain -between 1,200 and 1,700 metres (3,936 ft and 5,576 ft)- as does the Pyrenean Newt.
All things considered, the factors that have determined the milieu's characteristics are part of a well-ordered unity, making the most of a framework born of geological evolution. That circumstance gave birth, among the whole range of naturalistic disciplines, to scientific work proper to the considered mountain domain, the results of which are based on an exceptional sum of observed facts, obtained thanks to institutional dispositions for the protection of natural milieus, and judiciously dealt with by scientific research. The quality of this work deserves to be strongly underlined.
Naturalistic Survey - Professor Michel Clin - 14/01/2002