Climate is currently warming at a rapid pace, causing species to shift their ranges to follow the conditions they are adapted to. In arctic and alpine ecosystems, climate is warming at an even higher pace than the global average. Species range shifts to higher latitudes and elevations are a globally observed consequence, and species richness and vegetation productivity are increasing at highest latitudes and elevations. Yet, the limited empirical evidence available so far suggests that species’ warm range limits shift at least as fast as the cold limits at the global scale, resulting in contracting distributions of many species and, hence, increased extinction risks. Furthermore, both range limits seem to lag behind temperature trends, and the vast majority of publications report considerable amounts of variation between species-specific responses. These idiosyncratic responses imply asynchronous shifts and might result in reshuffled plant communities with novel biotic interactions. An improved understanding of the factors and processes determining the magnitude and velocity of species responses is pressing in a conservation context as arctic and alpine ecosystems harbour disproportionately high biodiversity, including rare and endangered species, and are in general poorly protected.