Vegetation changes on arid rangelands of the southwestern United States in the last 100 years are described. Reasons and solutions to the problems resulting from these changes are discussed. Shrubs have increased dramatically with a corresponding reduction of herbaceous plants. Encroachment of woody plants into previously shrubless areas is closely correlated with man's activities combined with drought. Man has been a disturber of natural systems and his ability to create disturbances has increased as technology has increased. Increased use of arid rangelands of the southwestern United States is possible with intensive practices such as brush control, revegetation where needed, and improved grazing management.