Urbanization

Some figures

In 1800, hardly 3% of the world population lived downtown, against 15% into 1900,50% about the year 2000, and with the current rhythm 65% of the population will be urban in 2025, and more than 80% in many countries. There are already in the year 2000,213 cities of more than one million inhabitants, and 23 méga-cities of more than 10 million inhabitants, and according to UNO (FNUAP), the urban population could still double within 100 years.

Urbanization and consumption of resources

The city consumes more or less renewable space and resources, in a limited world.
Les cities often occupies of rich person grounds, in alluvial zones and on the littoral .
Or, even if there exist experimental and marginal inclinations of autarkical districts or construction or more or less énergétiquement autonomous (Biosphere I, Biosphère II), the cities are never autonomous, and the urbanization is generally made with the detriment agriculture périurbaine. The City or the human settlement cannot exist without feeder agriculture, without the nature which produces 100% of oxygen vitally necessary to the inhabitants, without many peripheral resources necessary for construction, maintenance, the supply of energy and without the possibility of evacuating in continuous flow the billion gas tons of waste, solid and liquids which would asphyxiate in a few hours any rich big city locked up in a tight bubble. FAO promotes experiments of urban agriculture, in particular in the poor countries. In the years 1990, the approaches known as of Sustainable development highlighted that the economic models and urban dominant had produced not-durable and insupportable in the long term systems of habitat and production/transformation, transport and consumption. Forests/wood, water, air, ground, land, agriculture, fishings, wells of carbon, energies soft, clean, sure and renewable, management of waste, transport, etc will not be enough with the needs increasing for the periurbanisation, and thus become strategic domains and vital for the company. One speaks then about city renewed on itself, and the calculation of the ecological Empreinte transforms a confused presentiment into an obviousness and an alarm for the town planners and developers.

Urban pressure

Although energy efficiency progresses, and in particular in the rich countries, its positive effects are largely countered and cancelled by the energy wasting which has begun again for a few years and by the fact that the consumption of resource not, little, with difficulty or expensively renewable does not cease growing. The urban metabolism as conceived in the years according to war then at the era of the periurbanisation is particularly “greedy” in resources (space, energy, materials.). The calculation of the ecological print by pedagogically converting these resources into bioproductive equivalent-surface, much easier to visualize than the " tons equivalents of pétrole" , or ton-equivalent-poisons, or tons of gas with greenhouse effect, etc It is now enough to refer to surface productive emerged grounds, divided by the number of inhabitants to become aware of the real pressure which we exert on planet. The city dense, but built or rehabilitated with the principles of HQE (environmental High-quality) takes again its interest then.

Reasons of the urbanization

Many historical, political and sociocultural factors can explain the increasing urbanization:

The Rural migration and the development of a company turned towards the Industry and the service S made urban centres the primary source of employee job. The attraction Political Culture L and of the cities, in particular of the capitals, encourages the arrival of new inhabitants, in spite of chronic rises in rents and price of the land one. This price encourages a thickening of constructions and the exploitation of the basement (carparks, garages, trade sometimes)

The political decisions relating to the Town and country planning frame the existing urban development or create ex nihilo new cities. The Plane of occupation of the grounds (or POS) or the Local plan of town planning (or RAINED) and PADD, is in France the principal tools making it possible the communities to apply these policies. The techniques of Urbanisme durably direct the occupation of space in the cities, the elected officials and technicians being in addition confronted with many pressures contradictory of the inhabitants, tradesmen, industrialists, developers, etc

The tourist attraction of certain areas very sunny, snow-covered in winter or close to the Mer led to the development of a dense habitat. One speaks about mitage or urban spreading out, even of concreting of the Littoral to describe a progressive and inescapable occupation certain littoral valleys and . The term of Baléarisation indicates for example the construction of functional buildings on the entirety of the Sea front to accommodate in a massive way the tourists. The urbanization then destroys the Paysage even which gave birth to it.

Modes of urbanization

The cities can develop in a horizontal or vertical way, even both at the same time. The horizontal development is sometimes concentric, dendritic, or linear (frequent in the valleys, or on the edge of important axes), this according to the biogeographic, political or historical context (including the evolution of the historical conditions of property). Town planning is generally pressed on what exists, the grid system and one or more centers or poles (development multipolar). Many new cities were create. Except in the case of mushroom towns related to discovered gold seams, or resources quickly exhausted, or in the case of quoted touched by the repercussions of Tchernobyl, since the years 1700, it is rare that the cities are stabilized, disappears or decreases. Even Hiroshima and Nagasaki, or the shaven cities during the First World War or the second world war, or at the time of other conflicts quickly were rebuilt and developed. It is however only in the years 1970 with the new cities, and in years 1990 that the town planners started to think of the conditions of soutenability of the urban development. And it is necessary to wait the years 2000 for even appearing the first districts HQE (Bedzed for example in London) and 2006 for the first project of city HQE (in China).

Random links: