One third of Earth's land surface is classified as arid or semiarid, and approximately 15% of the world's population lives in these regions. As population and the demand for resources continue to grow, these sensitive landscapes face intensifying pressures and the threat of greater environmental disturbance. Understanding arid topography—the principal landforms found in arid-region structural settings—and the major geomorphic (landforming) processes operating in arid lands is fundamental to limiting disturbance and minimizing hazards in these areas. Weathered rock, crusts and pavements, slope failures, desert streams, desert piedmonts, desert lakes, and land-forms made by the wind are all influenced by the limited moisture availability in deserts.