ICG2022-292, updated on 20 Jun 2022
10th International Conference on Geomorphology
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Agricultural Policy triggers Land Degradation in the dry Mediterranean Southern Alentejo, Portugal (1986-2021)

Henrique Cerqueira1, Maria José Roxo1, and Adolfo Calvo-Cases2
Henrique Cerqueira et al.
  • 1CICS.NOVA, Universidade Nova de Lisboa - Faculdade de Ciências Sociais e Humanas, Lisbon, Portugal
  • 2Inter-University Institute for Local Development, Universitat de València, València, Spain

The scale and intensity at which human actions induces Land Degradation depends on which drivers are at play. Land management practices may provide the conditions for increasing or decreasing erosional processes, carbon emissions, water carrying capacity and vegetation cover, while Land Use Change (LUC) determines the spatial extent and magnitude of its effects. In Southern Portugal, especially the Eastern side of the Guadiana River, shallow and incipient soils, a semi-arid Mediterranean-type climate, and land use intensity all contribute to an important degree of degradation. Abrupt LUC can be traced back to the early 20th century when the commons were divided to be privately exploited on a yearly basis (1906-1926). Then, the autarkic policies of the Estado Novo Dictatorship converted large areas of poor soils to very intensive rainfed wheat crops (1929-1938), which culminated in vast areas of degradation and decreasing yields. The decades that followed were marked as a transitional period where some tenants were still trying to produce rainfed crops while others were converting towards pastures. As Portugal became a member of the EU and thus a partner in the common market, agricultural policy has since 1986 been a major driver for LUC and its effects in soils and productivity. This study used soil erosion data for different land uses from the Vale Formoso Soil Erosion Centre plots, a long data series (1961-Present), field observations and remote sensing data from the Landsat Series (1984-2021) are used to analyse changes in land use, vegetation cover and soil erosion from 13 sample areas within the Mértola Municipality. Results show a very high variability in erosion rates between land use classes, and a tendency towards volatility in change over time that has been exacerbated after the implementation of the Common Agricultural Policy of the EU. Finally, we present a conceptual model describing the temporal variability in erosion processes, discriminating their behaviour at hillslopes and valley floors and within land use / land cover changes, as well as an analysis of its consequences on the study area.

How to cite: Cerqueira, H., Roxo, M. J., and Calvo-Cases, A.: Agricultural Policy triggers Land Degradation in the dry Mediterranean Southern Alentejo, Portugal (1986-2021), 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-292, https://doi.org/10.5194/icg2022-292, 2022.