Urbanization

The process whereby an increasingly larger percentage of a given population lives in spatial clusters considered to be “towns” and “cities.” The criteria that qualify a settlement as “urban” frequently vary from country to country, meaning that what is considered an “urban place” in one location may not be defined as such in another nation-state. In the United States, the U.S. Bureau of the Census considers any place having a concentrated population greater than 50,000 inhabitants to be an “urban area,” and any population center of at least 2,500 residents outside of an urban area and having a community identity and name to be “urban.” Urbanization is typically associated with a number of related processes: industrialization, economic development, declining average family size, rising levels of literacy and education, and others. In some cases a single urban place will come to dominate a country’s urban geography in terms of both population size and economic function— this city serves as the primate city. In 2008 the United Nations estimated that for the first time in history, more than half of humanity lived in urban areas, and that the fastest rates of urbanization are occurring in the developing world. Urban places are not located on the landscape randomly. Many factors may affect the rate of growth of an urban area, including transportation linkages, natural resources located nearby, economic opportunities, and even the local physical geography can play a role in urbanization. Geographers have developed a number of approaches to explain the patterns of urbanization and to determine the characteristics that may influence urban growth and development. Central Place Theory holds that urban places are spatially arranged in a hierarchical framework, based on the sophistication of economic functions offered by each city or town.

Urbanization on a significant scale first took place in ancient Sumeria, along the course of the Tigris-Euphrates river system. The rich soils of these river valleys allowed for the production of an agricultural surplus, which in turn led to a differentiation of labor, development of social classes, and the emergence of more sophisticated economic and political systems than had previously been the case. The morphology of many early cities was haphazard and chaotic, but some urban areas in the ancient world were surprisingly organized and well planned. The city of Mohenjo Daro, established around 2500 BCE in the Indus River Valley, was clearly a planned settlement with streets and buildings constructed following a grid system, covered sewers, and a municipal garbage collection system! But in general, cities for much of history were places of squalor, congestion, and disease until the late 19th century. Pestilence typically spread quickly in urban areas, due to high population densities and poor sanitation. Industrialization and the agricultural revolution that accompanied it initiated a surge in urbanization that continues in many parts of the world, as thousands of rural workers migrated to the cities seeking employment. By the mid-20th century, zoning legislation, urban decentralization, the development of green belts, and other factors had lowered population densities and improved the quality of life in many urban areas in developed countries, while large cities in the developing world continued to struggle with the problems of pollution, overburdened transportation networks, and shortages of adequate housing and basic services.