Shrub encroachment, the increase in abundance or cover of woody species in areas where they were formerly absent or really scarce is a very contested process regarding its consequences for ecosystem functioning. Some scientists argue that shrub encroachment increase heterogeneity and concentrate scarce resources (water and nutrients) beneath them, therefore compromising plant growth (and with it forage availability and soil protection). Others, instead, see this process as a beneficial recovery from disturbances, with clear benefits on biodiversity, carbon sequestration and overall ecosystem health. In this chapter, I revisit the extend of shrub encroachment as a global phenomenon, which shows some particular characteristics in Spain. I also show in which context (in terms of climate, land use and plant cover) and for which ecological properties are we to expect either positive responses or detrimental effects from the encroachment of woody plants. I pay particular attention to the linkages between shrub encroachment and three widely use indicators of desertification, namely soil organic carbon, soil erosion and plant primary productivity.