Nomadic pastoralism is a form of pastoralism when livestock are herded in order to find fresh pastures on which to graze. However this distinction is often not observed and the term nomad used for both—in historical cases the regularity of movements is often unknown in any case. The herded livestock include cows, water buffalo buffalos, yaks, llamas, sheep, goats, reindeer, horses, donkeys or camels, or mixtures of species. Nomadic pastoralism is commonly practised in regions with little arable land, typically in the developing world, especially in the steppe lands north of the agricultural zone of Eurasia. Of the estimated 30–40 million nomadic pastoralists worldwide, most are found in central Asia and the Sahel region of North and West Africa, such as Fulani, Tuaregs, and Toubou, with some also in the Middle East, such as traditionally Bedouins, and in other parts of Africa, such as Nigeria and Somalia.