landscape resilience threshold in the desertification process of the pre- Andean valleys of Catamarca (Argentina)

Acta geológica 24 (1-2) 2012

Abstract

During the last four centuries the preandean valleys in northwestern Argentina suffered a severe process of desertification product of uncontrolled landuse, specially deforestation and overgrazing. The intensity of land degradation raises questions on the possibility (or not) of obtaining a sustainable future “agrosilvopastoril” production and, correlatively, on the aptitude to obtain the recovery of the landscape in the short or medium term. In Abaucán and Santa Maria valleys, sample areas that typify the conditions of the preandean arid region of northwestern Argentina, the causal factors and the historical evolution of the process of desertification were analyzed and if such a process has exceeded the capacity of recovery or resilience of the ecosystem. In Abaucán valley the intensity of the erosion in hillsides and piedmonts and the consistent contribution to the superficial drainage explain the changes in the fluvial pattern or “metamorphosis” of the Abaucán river. Additionally, the poor temporary recovery of the vegetation cover (specially in the piedmont levels covered by Larrea sp), suggests a decrease in the capacity of resilience of the landscape. In the Santa Maria valley, the evaluation of the erosive risk in different units of relief, expressed in loss of soil in Tn/Has/Year, validated by the null seasonal response of the vegetation cover allowed to infer that in the distal piedmont and the fluvial low terrace, the landscape would have reached “tipping point” or point of collapse of the ecosystem. Since different intensities of landscape deterioration coexist in the arid areas of the preandean valleys, an evaluation of the nearness (or distance) to the threshold of resilience is advised, a necessary condition to determine its productive sustentation, especially under the perspective of future climate changes.