Transhumance is a type of mobile pastoralism in which grazing livestock are moved (droved) in herds seasonally between several fixed pastures, in contrast to sedentary pastoralism, where the livestock remain all year round on the same area of land, known as a ranch; and nomadic pastoralism, where the livestock are moved irregularly or randomly among different regions in search of any usable pastures. In montane regions, it implies livestock movement between the higher-altitude alpine steppes in summer and the alluvial grasslands in the lowland valleys in winter. In contrast, seasonal movement across the same plains or plateaus is typically done due to limited forage yield from a single patch of pasture and/or to avoid overgrazing, and is more susceptible to disruption by climatic, economic or political change as with any cross-region livelihoods.