For thousands of years, large areas of northern Africa have been inhabited by people who have travelled with all their belongings, including animals. A study of the nomadic way of life reveals that nomadic social systems often appear to represent very efficient use of resources in a harsh natural or social environment. Gatherer nomads who do not produce food but hunt and gather it. Examples of these include the Pygmies of Zaire's Ituri forest, the Bushmen of the Kalahari desert, and some Australian Aborigines.
Pastoral nomads breed animals for food and move in search of pasture and water.
Trader nomads move where there is a market for their goods and skills. Examples include Gypsies in many countries. Many of the people belonging to nomadic groups are heirs to ancient customs and a way of life which could be considered sustainable. Pastoral nomads, for example, allow their animals to graze the land least suitable to farming, such as mountain and desert regions. They allow their animals to graze the natural vegetation rather than sowing or storing fodder.