Results/Conclusions The decline observed on the studied Scots pine forests was associated to the local level of drought stress experienced at each plot. In addition, stand structure, soil properties and mistletoe infection, as well as their interaction, contributed to the observed defoliation and mortality patterns, presumably acting as predisposing factors. Recruitment of Scots pine was low in all plots. In contrast, we observed an increase in the recruitment of other tree species, mostly Quercus ilex (evergreen) and Q. humilis (deciduous), in plots where Scots pine showed high defoliation and mortality. These results suggest an altitudinal upwards migration of Quercus species in the studied slopes, and that this migration is mediated by the dieback of the dominant canopy species. In the mid term, this trend is likely to result in a vegetation shift in the study area, from pine-dominated to broadleaves-dominated forests. We hypothesize that many of the scattered populations of Scots pine sheltered in the mountain environments of the Iberian Peninsula could be at risk under future climate scenarios.