The role of land use and land cover changes in triggering soil losses in the SE Alentejo, Portugal

This study analyses and interprets the effects of historical and contemporary land use and cover changes (LULC) on soil erosion in the Serra de Mértola region, Portugal, by using the 58 years of measurements in 8 × 22 m erosion plots at the Vale Formoso Erosion Centre and employing methodologies including field observations, aerial image analysis and Landsat NDVI trend assessment. Land cover and management changes, influenced by agricultural policies since the early 20th century, notably during the wheat campaigns of the fascist regime, have exacerbated soil erosion, with the highest rates observed in vertical fallow (964 g m⁻² yr⁻¹), wheat (90 g m⁻² yr⁻¹) and horizontal fallow (66 g m⁻² yr⁻¹). These practices continue to be somewhat relevant today, as cereal production is still being subsidized. However, Quercus, Pines—introduced since agrarian reforms and Portugal's entry into the common agricultural policy (CAP)—and spontaneous vegetation from CAP's set-aside policies and recent land abandonment trends show lower erosion rates, underlining vegetation's role in erosion protection. Using NDVI trend analysis, we distinguish between natural fluctuations and land cover changes impacts. Understanding these changes and how they relate to slope and valley floor dynamics, such as incision, aggradation or stabilization, is crucial for recognizing human influences on the earth's surface. Our research highlights sustainable land management's role in reducing soil erosion in desertification-prone areas.