LAUSR

Abstract Southern Spain is characterized by a longitudinal pluviometric gradient over a distance of approximately 260 km, where the annual rainfall ranges from 1668 mm y−1 in the west (Sierra de Grazalema) to only 150 mm y−1 in the east (Cabo de Gata). Along this gradient during the last 70 years there have been trends of increasing rain in the west and increasing aridity in the east. The threshold annual rainfall level separating these regions is approximately 500 mm. For this study we selected two experimental basins having different geo-morphodynamic variables, each representing one side of this threshold. We used these basins for analysis of changes in land use and characterization of physiographic, soil cover, physical, chemical, and hydrological variables. We developed a database, applied statistical normalization, and then performed principal component analysis to identify the main geomorphological components explaining the variance. Our quantitative and cartographic results identified particular factors (vegetated areas, water resources, and soil degradation) that most control geomorphological processes, and explain the landscape dynamics in this region over recent decades.