drought, abnormally long period of insufficient rainfall. Drought cannot be defined in terms of inches of rainfall or number of days without rain, since it is determined by such variable factors as the distribution in time and area of precipitation during and before the dry period. Since ancient times droughts have had far-reaching effects on humankind by causing the failure of crops, decreasing natural vegetation, and depleting water supplies. Livestock and wildlife, as well as humans, die of thirst and famine; large land areas often suffer damage from dust storms or fire. Drought is thought by some to have caused migrations of early humans. In India and China drought has periodically brought widespread privation and death. In 1930 lack of rainfall devastated the Great Plains of the United States; called the Dust Bowl, its area spread to alarming dimensions (about 50 million acres). During 1962 much of the eastern part of the United States experienced the worst drought in more than 50 years. Some two thirds of the United States experienced drought that combined with some of warmest temperatures on record in the summer of 2012. Since the 1960s severe, sometimes recurring droughts have afflicted countries in many parts of Africa. Clearcutting of trees for firewood, overgrazing, and overcultivation, which lead to land degredation, contribute to this drought cycle.
See C. S. Russell et al., Drought and Water Supply (1970); W. C. Palmer and L. M. Denny, Drought Bibliography (1971); R. V. Garcia and J. Escudero, Drought and Man (1986).