1 Faculty of Geography, University of Tehran, Tehran, Iran
2 Faculty of Environment, University of Tehran, Tehran, Iran
3 Geography and Urban Planning, University of Tehran, Tehran, Iran
International Journal of Environmental Research
University of Tehran
Vol. 1, Num. 3, 2007, pp. 252-257
ABSTRACT
About half a century ago, following the introduction of urban sprawl up concept, various studies have been conducted to describe the mechanism and the formation of this phenomenon. Some of these studies aimed at finding the negative and positive impacts of such phenomenon on urban area with emphasis on how such concept may be looked open from environmental, economical and social perspectives.The main research objective, in this article, focuses on adverse impacts of urban sprawl on air pollution in a mega city such as Tehran. Therefore, attempts have been made to show a relationship between urban sprawl up and the increase in air pollutants concentration. Three methods have been investigated to validate such a concept methodologically. Tehran has been chosen as a case study to further demonstrate validity of such a correlation between urban sprawl up and rise in air pollution scientifically. The results confirmed a function relating air pollution increase to urban sprawl up.
INTRODUCTION
Urban “sprawl” is a word that has entered into the literature of urban planning since half a century ago, and up to now; various definitions have been presented such as:
“A pattern of land use in an urbanized area that exhibits low levels of some combination of eight distinct dimensions: density, continuity, concentration, clustering, centrality, nuclearity, mixed uses and proximity (Glaster et al., 2001)”.The term is also used variously to mean the gluttonous use of land, uninterrupted monotonous development, leapfrog discontinuous development and inefficient use of land (Peiser, 2001).
According to the Vermont forum on sprawl: Sprawl is dispersed, auto-dependent development outside of compact urban and village centers, along highways, and in rural countryside (Menon, 2004). Dieleman and Wegener (2004) suggest that causes of urban sprawl can be grouped into two categories: the general drift of socio-economic change in developed societies and government spatial planning policies, and conclude that in the absence of strong planning interventions at regional and local levels, further urban deconcentration is likely to occur (Dieleman& Wegener, 2004).
There is one basic difference between the causes of urban sprawl in a developed country and that of a developing country. Sprawl in developed countries is usually a matter of preference. It may have begun with the industrial revolution, and later reinforced by government policies. The entire culture in developed countries (especially the USA) is centered on automobile use. This coupled with government policies that encourage the move to sub-urban areas, and subsidize the use of private transport has fuele urban sprawl in the developed world to a great extent (Menon. 2004).
The story in developing countries is different. In a developing country such as Iran, sprawl is fueled more by necessity. A lot of the underlying causal factors are historical, and have built up over a number of years. Sprawl, in Iran, is concentrated around certain pockets of dense human population the mega cities. The causes of sprawl here can be traced to historical reasons too.
Most often to the colonial legacy that some developing countries have acquired, for example in Iran mega cities, such as Tehran, were developed as administrative centers, transportation hubs, where people from the rural areas came in search of employment and stayed on. These became central cities after the colonial masters left. The growth of these mega cities was unplanned and gradual. This trend has continued into the post-colonial period too. Most of these mega cities remain the dominant source of employment, education and so forth. And therefore people still migrate from the rural areas. In certain developing countries, since the majority of the population is poor and in need of employment, they usually move to the cities to look for a better standard of life. This has led to burgeoning centers of urbanization that are growing outward, away from the city center. However, as these countries are urbanized at rapid rates, these pockets are increasing and so is the problem of sprawl (Taghvayee & Sarayi. 2003).
Studies and data show that in Iran, the capital Tehran has encountered with urban sprawl and the problems resulting from it. So population of this city has changed from 210 thousand people in 1921 to 702 million in 2000. At the same time, area has changed from 720 to 73950 hectare in this period of time. Better stated, the population has increased by 33 times but the area has become 109 times more. (The statistic center of Iran and comprehensive plan of Tehran).Urban sprawl in Tehran has resulted in many negative consequences in environmental, economical and social dimensions. One of the most important environmental effects of urban sprawl is the increase in air pollution.
In spite of the fact that the causes of urban sprawl in developed and developing countries are different, it has the same results and consequences. Some impacts and results of urban sprawl are: the extermination of desirable agricultural lands around the city, the cost increase in urban infrastructures and services, the cost increase time and length of inner city trips, the increase of energy consumption, the existence of vacant and depleted lands in the cities, social segregation, the increase of road transportation specially private cars, air pollution and so on.
Studies in North American cities show that “sprawl” in those cities has caused the extermination of 1.5 million hectares ofagricultural lands (Benfield and Raimi. 1999) or in Australian cities the cost of infrastructures and services has noticeably increased as a result of this phenomenon. (Frunk & Pivo. 1995). In Liverpool as a city inflicted by sprawled through the 20th century, the ecological and spatial segregation of social classes increased. Despite some counteracting policies this trend towards increased segregation seems to be continuing. (Couch & Karecha. 2006). Burton (2001) found that where there was a large proportion of high density housing, segregation tended to be low. Density seemed to be a key factor in limiting segregation; segregation would be less across the whole of a more compact city.
One of the most important environmental results of urban sprawl is the deterioration of air quality.
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CONCLUSION
Tehran, as capital of Iran, has today encountered with urban sprawl, scattered and spread, and this phenomenon has had very undesirable effects on environmental, social and economical dimensions. One of its most important undesirable environmental effects is air pollution in this city, such that today, Tehran is one of the most polluted cities in the world. The relationship between two variables, urban sprawl and air pollution, in this paper is considered in three methods. In this paper urban sprawl in Tehran as a cause of the increased length of urban travels, a desirable publicmeans oftransportation in this city has not been implemented or urban sprawl causes more and more use of private cars, in other words, this has prevented a desirable public transportation being implemented in this city, settlements and towns in the periphery and suburban of Tehran are the kinds of dormitories and satellites settlements, and because of this much transportation and traffic in early and ending hours of work between city center and towns and surrounding areas and settlements are taking place.
These three factors cause the increase of fossil fuels used in motorized vehicles and the increase of many pollutants emission in the air of this city air and this causes air pollution of Tehran city.
Result of this research can help to urban planners to gain urban sustainable development. Consequences of this study may conduct to modify the physical pattern of urban development for reducing urban sprawl. Some strategies such as: compact city, urban smart growth, increasing population and building density are used to controlling this phenomenon as an efficient approach.
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