Urban space
The definition of urban space (or, also, urban area, urban environment, urban area, urban center, urban core, urban area or urban territory) is as difficult as rural space (or that of the peri-urban space, which includes the space between the last two), especially after the latest models of urban growth.
The characteristic features of urban space are its high population density, its extension and its greater endowment of all kinds of infrastructures; but above all the particularity of urban functions, especially economic ones, concentrating activity and employment in the secondary and tertiary sectors, the primary being insignificant. The urban space, compared to its area of influence, is an issuer of services of all kinds (bureaucratic, educational, health, financial, cultural, leisure) and products with high added value; while it is an attractor of population and other types of resources.
The high price of land, a result of the high demand for housing, commercial premises and all kinds of economic activities, the lack of homogeneous infrastructure in the city and the lack of adequate land tax collection, reinforces densification in height, even though this is also a product of the importance of location The rural space, with the passage of time, has acquired urban behaviors in its population, activities and infrastructure endowment, diluting to a certain extent the differences with the urban one in terms of the satisfaction of the needs of elementary services.
Definitions
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Chinese
Since the year 2000, Chinese cities have expanded at an average rate of 10% per year. China's urban population is estimated to increase by 292 million people by 2050, when its cities are home to a combined population of more than 1 billion. The country's urbanization rate increased from 17.4% to 46.6% between 1978 and 2009. Between 150 and 200 million migrant workers work part-time in large cities and periodically return to the countryside with their earnings.
Today, China has more cities with one million long-term residents or more than any other country, including the three global cities of Beijing, Hong Kong and Shanghai; by 2025, the country will be home to 221 cities with more than one million inhabitants. The figures in the following table come from the 2008 census, and are only estimates of urban populations within the administrative limits of cities; there is a different classification if the total municipal populations (which includes suburban and rural populations) are considered. The large "floating populations" of immigrant workers make it difficult to conduct censuses in urban areas; the figures below only include long-term residents.
Japan
In Japan, built-up areas are defined as contiguous areas of densely inhabited districts (DIDs) using the enumeration districts as units with a density requirement of 4,000 inhabitants per square kilometer (10,000/sq mi).
United States
There are two categories of urban areas in the United States. The term urbanized area denotes an urban area of 50,000 or more people. Urban areas with less than 50,000 people are called urban conglomerates. Urbanized areas were first delineated in the United States in the 1950 census, while urban agglomerations were added in the 2000 census. There are 1,371 urban areas and urban clusters with more than 10,000 people.
The United States Census Bureau defines an urban area as "core census block groups or blocks that have a population density of at least 1,000 people per square mile (386 per square kilometer) and census blocks surrounding areas that have a general density of at least 500 people per square mile (193 per square kilometer)".
The largest urban area in the United States is the New York metropolitan area. The population of New York City, the core of the metropolitan area, is over 8.5 million people, its metropolitan statistical area has a population in excess of 20 million, and the population of its combined statistical area is over 23 million. The next seven largest urban areas in the US are Los Angeles, Chicago, Miami, Philadelphia, San Francisco, Houston, and Atlanta. About 82% of the US population lives within area boundaries urbanized as of December 2010. Combined, these areas occupy about 2% of the US land area. Many Americans live in agglomerations of cities, suburbs, and towns adjacent to the largest city in the metropolitan area.
Indian
For the 2011 Census of India, the definition of an urban area is a place with a population of at least 5,000, with a density of 400 people per square kilometer or more, and with 75% or more of male population employed in non-agricultural activities. Places administered by a municipal corporation, a cantonment board, or a notified urban area committee are automatically considered urban areas.
The 2011 Census of India also defined the term "urban agglomeration" as an integrated urban area formed by an urban nucleus together with its "outgrowths" (adjoining suburbs).
Brazil
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According to IBGE (Brazilian Institute of Geography and Statistics) urban areas already concentrate 84.35% of the population, while the Southeast region continues to be the most populous, with more than 80 million inhabitants. The largest The metropolitan areas of Brazil are São Paulo, Rio de Janeiro and Belo Horizonte, all of them in the Southeast Region of Brazil, with 21, 12 and 5 million inhabitants respectively. In general, the state capitals are the largest cities in their states, except Vitória, capital of Espírito Santo, and Florianópolis, capital of Santa Catarina. There are also non-capital metropolitan areas in the states of São Paulo (Campinas, Santos and the Paraíba Valley), Minas Gerais (Acero Valley), Rio Grande do Sul (Sinos Valley) and Santa Catarina (Itajaí Valley).
Urban environment
Culture
Urban culture is the culture of cities. The theme that defines it is the presence of a large number of very different people in a very limited space, most of whom are strangers to each other, which makes it possible to create a wide range of subcultures close to each other, exposed to the influence of others, but without necessarily intruding on people's private lives.
Climate
Several factors influence urban climate, including city size, city morphology, land use configuration, and geographic environment (such as relief, elevation, and regional climate). Some of the differences between urban and rural climates are air quality, wind regime, and changes in the rainfall regime, but one of the most studied is the urban heat island effect.
Temperature and heat island effect
Urban environments are often warmer than their surroundings, as documented over a century ago by Luke Howard. Urban areas are large-scale islands or blobs compared to their more rural surrounding terrain. The spatial distribution of temperatures occurs along with temporal changes, both causally related to anthropogenic sources.
The urban environment has two atmospheric layers, in addition to the planetary boundary layer that lies outside and extends high above the city: (1) The urban boundary layer is due to spatially integrated heat and moisture exchanges between the city and its overlying air. (2) The surface of the city corresponds to the level of the urban canopy layer. Flows across this plane include flows from individual units, such as rooftops, canyon tops, trees, lawns, and roads, embedded in larger land-use divisions (eg, suburbs). The urban heat island effect has been one of the main focuses of attention in urban climate studies and, in general, in the effect that the urban environment has on local meteorological conditions.
Pollution
This field also includes the issues of air quality, radiation fluxes, microclimates and even issues traditionally associated with architectural design and engineering, such as wind engineering. The causes and effects of pollution, as understood through urban climatology, are becoming increasingly important for urban planning.
Precipitation
Changes in winds and convection patterns over and around cities affect precipitation. Contributing factors are believed to be the urban heat island, increased surface roughness, and increased aerosol concentration.
Decay
Urban decay (also known as urban rot, urban death, and urban blight) is the sociological process by which a previously functioning city, or part of it, falls into disrepair and decrepitude. It can be characterized by deindustrialization, depopulation or disorganization, economic restructuring, abandoned buildings and infrastructure, high local unemployment, rising poverty, fragmentation of families, low standard and quality of life in general, disenfranchisement, crime, high levels of pollution and a desolate urban landscape, known as a greyfield or urban prairie. Since the 1970s and 1980s, urban decay has been associated with Western cities, especially in North America and parts of Europe (especially the United Kingdom and France). Since then, major structural changes in global economies, transportation, and government policy have created the economic and then social conditions that gave rise to urban decay.
City of multiple exchanges
There are different ways of seeing and reading the city. One of the most important notions is the city as a space for multiple exchanges. The city can be proposed as a cultural space that brings together various functions: the official and the recreational; the material and the symbolic. It contains the village, the temple, the square and the theater, it is a "locus of collective memory, a space for desire, the imaginary and writing". The city represents power and sacralizes it, but even more, "it polarizes, stores and transmits culture". Interestingly, the language represents the culture better than the city could represent it.
On the other hand, according to Henri Lefebvre, the city is the “projection of society on a terrain; not only on the sensible space but on the specific plane perceived and conceived by thought, which determines the city and the urban”. In addition, he adds that "the space of a city is characterized by its simultaneity", it is governed by a relationship between time and space.
Holanda Izquierdo proposes the reading of the city as if the city were a text, built by various economic, cultural and social conditions, where various social and mental forms are expressed. If we start from the notion of the city as a text, then it “has its own language”. Within the reading of it, we can find a relationship "between the urban and the textual structure" in which we can associate it with a walker walking through the city and a reader reading a text. The city is not only a system, but is built by several interrelated systems: the fundamental structure that occupies the urban space, factors such as zoning, location, history and development and infrastructure, and finally, its "particular poetics" that determine the readings of that city. Which means that the textual structure of the city is like a "collage", that we can go through inexhaustibly and that has a unique language. As Roland Barthes points out: the city speaks to its inhabitants and they speak to the city.