If reported separately for urban and rural area, it provides a measure of urbanization. The high growth of urban populations, caused by rates of natural increase (excess of births over deaths) in urban areas, migration from rural to urban areas and the transformation of rural settlements into urban places, is of concern in many countries. In settings where the conditions for sustainable agricultural and rural development are not in place, high rates of rural population growth could negatively affect the use of land, water, air, energy and other resources.