Urbanization is the study of the social, political, and economic relationships in cities, and someone specializing in urban sociology would study those relationships. There is no strict dividing line between rural and urban; rather, there is a continuum where one bleeds into the other. However, once a geographically concentrated population has reached approximately 100,000 people, it typically behaves like a city regardless of what its designation might be.
There are three prerequisites for the development of a city. First, good environment with fresh water and a favorable climate; second, advanced technology, which will produce a food surplus to support non-farmers; and third, strong social organization to ensure social stability and a stable economy. Most scholars agree that the first cities were developed somewhere in ancient Mesopotamia, though there are disagreements about exactly where. Most early cities were small by today’s standards, and the largest city around 100 CE was most likely Rome, with about 650,000 inhabitants. The factors limiting the size of ancient cities included lack of adequate sewage control, limited food supply, and immigration restrictions. For example, serfs were tied to the land, and transportation was limited and inefficient. Today, the primary influence on cities’ growth is economic forces.
Growth of Urban Populations
Urbanization levels are affected by two things – migration and natural increase. Migration is the movement of population from one area to another. Some migrations are forced, voluntary, permanent or temporary, international or regional. Rural to urban migration is the movement of people from the countryside to city areas. This type of migration happened in developed countries from the 18th century onwards on a large scale and has gradually slowed down. However, many developing countries are experiencing massive rural to urban migration, mainly of young males, into the major cities.
The major reasons for migration can be classified into push and pull factors. A push factor is something that can force or encourage people to move away from a country. Push factors can include famine (as in Ethiopia in the 1980s), drought, flooding, a lack of employment opportunities, population growth, overpopulation, and civil war. A pull factor is one in which encourages people to move to a city. Pull factors include the chance of a better job, better access to education and services, a higher standard of living. These factors have contributed to millions of people in developing countries moving to cities, creating mass urbanization. Urban populations can also grow as a result of natural increase (a population increase due to more births and fewer deaths). Natural increase is stimulated by better access to medical care, improved water supplies, sanitary conditions, and wealth.
Suburbs and Exurbs
As cities grew and became more crowded (and often more impoverished and costly) more and more people began to migrate back out of them. But instead of returning to rural small towns (like they had resided in before moving to the city), these people needed close access to the cities for their jobs. In the 1850s, as the urban population greatly expanded and transportation options improved, suburbs developed. Suburbs are the communities surrounding cities, typically close enough for a daily commute in, but far enough away to allow for more space than city living affords. The bucolic suburban landscape of the early 20th century has largely turned into sprawl.
Urban sprawl refers to low-density development in rural areas. It contributes to traffic congestion, which in turn contributes to commuting time. Commuting times and distances have continued to increase as new suburbs developed farther and farther from city centers. Simultaneously, this dynamic contributed to an exponential increase in the use of natural resources such as fossil fuels, which sequentially increases pollution in the form of carbon emissions.
As the suburbs became more crowded and lost their charm, those who could afford it turned to the exurbs, communities that exist outside the ring of suburbs and are typically populated by even wealthier families who want more space and have the resources to lengthen their commute. As cities evolve from industrial to post-industrial, the practice of gentrification becomes more common. Gentrification refers to members of the middle and upper classes entering city areas that have been historically less affluent and renovating properties while the poor urban inhabitants are forced by resulting price pressures to leave those neighborhoods. This practice is widespread and results in economically disadvantaged people being pushed into increasingly decaying portions of cities.
Together, the city centres, suburbs, exurbs, and metropolitan areas all combine to form a metropolis, or densely populated city. New York was the first North American megalopolis, a huge urban corridor encompassing multiple cities and their surrounding suburbs. The Boston to Washington DC corridor on the East Coast of the UNited States is an example of a megalopolis. In general, metropolises use vast quantities of natural resources and are a growing part of the North American landscape.