Geomorphic and hydrological effects of traditional shifting agriculture in a Mediterranean mountain, Central Spanish Pyrenees

Abstract

Shifting agriculture occupied large areas of middle latitude mountains during periods of strong demographic pressure. On average, this practice accounted for about 22.8% of the total cultivated area in the Central Spanish Pyrenees at the beginning of the 20th century. The use of experimental plots between 1992 and 2003 demonstrated that shifting agriculture increased overland flow, suspended sediment and solute concentration. Total soil loss was about 14 times higher under shifting agriculture than under dense shrub cover, and almost 3 times higher than permanent sloping fields. Erosion rates ranged between 0.1 and 1.4 t yr-1. The abandonment of shifting practices resulted in rapid plant recolonization and a decrease in runoff and soil erosion. Nevertheless, severe geomorphic processes are still active several decades after abandonment, explaining landscape degradation and the triggering of shallow landslides.