Boreal and arctic base-rich scree and block fields comprise talus or freeze-thaw block fields of calcareous rocks in the southern boreal to arctic regions, mainly in the Scandinavian Mountain range, Iceland and Svalbard. Because of the large variation in climate, the habitat harbours a large diversity of species and plant communities, but this habitat includes only the sparse assemblages of vascular plants growing in sparse patches. These are dependent on the natural or seminatural disturbance regime, periodic rockfall and continuing instability of the substrate in the case of screes, and in some regions also a long tradition of grazing.