Urbanization

The urban world at the dawn of the 21st century has assumed special importance for two principal reasons. First, the world's population has recently crossed the threshold from being more rural to being more urban. In absolute terms and according to UN estimates, this means that of the world's population of approximately 6.8 billion, approximately 3.5 billion people (or 51%) are living in urban settings. To put this notion in historical context, consider that 58 yrs. (years) earlier only 29% of the world population lived in cities. The projection for 2050 is 70%. Second, a dramatic change in the urban hierarchy is taking place as the large cities—variously termed global cities, world cities, megacities, and so on—are beginning to dominate the urban landscape. This entry first reviews the historical development of the urban world, from the earliest settlements in Mesopotamia to the present, and the types of explanations researchers have used to describe this process. Problems in measuring the degree of urbanization are then discussed, including the concept of urban degree (the level of a country's urban concentration, expressed in percentage at a point of time). Although urbanization is occurring around the globe, there are significant differences in this process; some of the global trends are noted here. The entry concludes with a look at the future of urbanization.

Along with urbanization, other changes are taking place concomitantly: The rural-urban and interurban mobility of population is accelerating, the traditional rural-urban dichotomy is blurring, and research and technological innovations in economic development and transportation—along with the relaxation of political-institutional barriers—are growing. Consequently, a diversified and unprecedented mix of urban phenomena, urbanization processes, and urban patterns in global and regional scales is emerging, giving rise to complex issues, problems, and prospects. The concentration of urban populations is manifested in many forms and functions—both historically, through cyclical changes (e.g., urbanization, de-urbanization, and re-urbanization), and spatially, from the monocentric, core-oriented settlements to the polycentric, peripherally focused patterns.

Urban fringe, urban cluster, urban sprawl, “rurban,” and extended urban areas are among the terms frequently used to identify and characterize the spatial patterns of the emerging urban landscapes. Urbanization is linked with social and demographic changes such as smaller family sizes, occupational specialization, and increased population densities. Ideally and typically, urbanization is tied with increasing wealth and improved quality of life. While an urbanizing world has the potential to impart extraordinary benefits—including an enhancement of the quality of life—to its citizens, it also faces significant problems that include the degradation of environment and a challenge to urban sustainability. Urbanists seek to analyze these diverse urban issues from a variety of perspectives and scales in order to understand the spatial processes and patterns.