Land abandonment is a widespread phenomenon in Spain, particularly in Mediterranean mountain areas and semi-arid regions, where it constitutes a key driver of land degradation and desertification. This chapter analyses the environmental consequences of farmland abandonment, with a specific focus on soil erosion and conservation processes. While land abandonment can initiate ecological succession and lead to the recovery of soil quality, this outcome is not guaranteed. In many cases, degradation processes persist or intensify, especially where cultivation had previously exhausted soil fertility, where traditional soil and water conservation practices, such as terracing, have been abandoned, or where recurrent wildfires inhibit vegetation regrowth. In semi-arid environments, low rainfall and high soil erodibility further constrain vegetation recovery, facilitating crust formation, runoff concentration, and gully development. Drawing on evidence from various Spanish regions, the study underscores the importance of site-specific management strategies aimed at mitigating the adverse impacts of abandonment and enhancing ecosystem services. Without appropriate interventions, land abandonment may exacerbate erosion, reduce biodiversity, and increase the risk of irreversible degradation, compromising long-term sustainability in vulnerable landscapes.