Temperate alpine grasslands and shrublands occur above the treeline, on temperate and boreal mountains worldwide. Seasonal productivity is limited by cold and snow cover, often with strong winds. Mosses, liverworts, lichens, flowering plants and low shrubs generally form a continuous cover, except where strong winds and dry conditions limit vegetation to sparse lichens and dwarf shrubs. Most fauna is seasonally active during warmer summer months, with insects and vertebrates having adaptations to extreme cold, including hibernation. Many species have restricted distributions, with strong barriers to dispersal between mountains.