In sub-Saharan Africa, variations in the natural environment have a strong influence on the spread of animal traction. There is a long tradition of animal traction use especially in the high-altitude zones of Ethiopia. It has spread to the semi-arid and sub-humid zones but is still marginal in the arid and wet zones. In the semi-arid and sub-humid zones, animal traction is used for extensive farming and not for agricultural intensification; this is not as was planned by development programmes. Irrational agricultural practices, including improper use of animal traction, have often aggravated environmental degradation. Animal traction has generally led to an expansion of cropped area and the development of cash crops, but it has rarely raised crop yields per unit area. It has often been used for other, more profitable, purposes including transport livestock production, land ownership and contract labour.