Urbanization

Urbanization is the general process by which essentially rural societies and the regions they occupy transform into predominantly urban ones, usually occurring over long periods of time, involving substantial redistributions of people in space, and concentrating proportionally more and more of them in towns and cities. Urban places and their communities differ principally from rural ones by exceeding certain thresholds of population size, physical density, territorial extent, administrative status, functional complexity, and morphological diversity, beyond which they are considered unquestionably urban in character.

A host of interrelated transforming processes drive urbanization. Foremost among them is economic change, but others include demographic, political, cultural, social, and technological changes as well as shifts in natural resource use. All of these are shaped fundamentally by geographically and historically contingent circumstances.

In theory, the process has a beginning, when towns and cities appear for the first time within a previously wholly rural settlement area, and an end, when virtually all people live concentrated in urban places. Most regions fall somewhere between these extremes of urbanized degree (at the continental scale between 37% and 80% in 2000), depending on the type and extent of their economic development and the interplay of these and other factors. Urbanization is seen as a permanently transforming societal process that is diffusing historically across the globe. Consequently, the earth's regions consistently display immense geographic variation in the extent and form of their urbanization. The organization of urban systems (i.e., networks of cities), land use, social geography, infrastructure and built environment, and townscape character reflects such variation.

Urbanization can be observed, measured, analyzed, and understood at many geographic scales—from localities of a few square kilometers or miles, to regions such as metropolitan areas, to regions of a larger extent such as states, to nations, to continents.