Cambios históricos en los usos del suelo en la Vall de Boí (Alta Ribagorça, Lleida) y sus repercusiones en el territorio

The rapid change occurred throughout the 20th century in the Pyrenees from a traditional society to a society integrated in a competitive economy, process that occurred in parallel with an intense migratory flow to urban areas, has changed the relationship between society and territory. As a result of this change, a widespread abandonment of traditional activities was initiated, which resulted in a gradual restructuring of the economy to the point that services and tourism are configured as the most important economic sectors. From this approach, the studied area is located in the Vall de Boi (Alta Ribagorça, Lleida), a Pyrenean valley affected by depopulation until the late 1980s, when it simultaneously started a continued recovery of the population and tourism became an economic pillar, through the exploitation of their natural (ski station and the National Park of Aigüestortes i Estany de Sant Maurici) and cultural (Romanesque churches) resources. The main objective of the study aims to determine the role of the primary sector (livestock, agriculture and forestry) in the evolution of land use during the period from 1956 to 2008. To that end, the main changes in land use will be studied and analyzed and it will be attempted to establish if environmental variables - plot area, elevation, slope, aspect, radiation- intervene in a meaningful way in this process of change. The methodology is based on an analytical combination of cadastral layers from 1956 and 2008 carried out with the help of GIS, from which the major changes that have occurred during the studied period are assessed and are correlated with their relationship to environmental variables. Also, through T-Student statistical test, the significance of the environmental variables in relation to changes in land use during the studied period is verified. Finally, in order to know the intensity of changes, these are classified in different degrees discriminating whether their evolution is in the forward direction -due to the abandonment/ minimization of agricultural activity-, or if their evolution is in the reverse direction -as a result of intensified human activity or action of natural agents such as avalanches, landslides or spontaneous wildfires-. The main results show that the studied area is undergoing a very fast revegetation process indicating that most changes are in the forward direction and with a high degree of intensity, which involves the loss of grassland and crops for mature forests such as pine forests and scrubland. Also, the revegetation process occurs unevenly in the territory, so that the land with a slope greater than 25o and located at an altitude between 1.900-2.300m is the most vulnerable to changes. Findings suggest that the Vall de Boí is experiencing a rapid homogenization of the landscape as a result of the abandonment of traditional activities. This causes that more mature forest uses, such as pine and scrub, are becoming main uses, marginalizing less evolved uses due to human pressure, such as crops in the valleys and pastures in upper highlands