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Population Density

Population density in 1994, region by region.
Population density in 2006, country by country.

The population density is a measure of the number of individuals of a population occupying a given portion of a medium, and although it can be used for any tangible object, it is most often applied to living organisms. The population density is usually expressed in terms of individuals per unit area.

Summary

/ / Population density biological

The population density is a common biological measurement and is often used by conservationists as a more appropriate value than absolute numbers. Low population densities may create a spiral of extinction, where low densities lead to fertility increasingly reduced. This effect is called Allee effect , after WC Allee , who put the first light. For example:

  1. Greater problems in finding partners in areas of low density.
  2. An increase of inbreeding in areas of low density.
  3. Susceptibility to catastrophic events increased in areas of low density.

However, note that different species present at the base of different densities. For example, the r-strategy species usually have a high population density, while the K-strategy species may have a lower population density. A low population density may be associated with adaptation to a specialization in the location of reproductive partners, such as specialized pollinators such as those found in the family of orchids.

It is also possible to define the density of a population through its biomass. This method is useful when you have to compare the densities of species of size or nature very different.

Human population density

Photomontage of satellite images: the earth at night. The illuminated areas materialize conurbation areas, major transport routes, and the phenomenon, recently said of light pollution
4 regions in France are mainly concerned with a very high population density
The spatial and temporal variation of population density (here on the territory of Belfort is one of the elements of interest for Planning. They are also, in part, the effects of this development

For humans, we define density as the number of people per unit area (which may or may not inland waters), although it can also be expressed in relation to habitable land, inhabited arable (or potentially arable) or cultivated.

It is frequently expressed in persons per square kilometer or per hectare is obtained simply by dividing the number of people considered by the area measured in square kilometers or hectares.

In practice, one can calculate this for a city, town, country or the world.

For example, for most countries European large size (thereby integrating dense areas and other less populated areas), the average density ranges between 100 and 393 inhabitants per square kilometer ( France : 94 hab /. km 2 (counting Guyana), Germany : 231 inhabitants / km 2,Netherlands : 393 inhabitants / km 2United Kingdom : 244 inhabitants / km 2). An area very desert has meanwhile density close to or even less than one inhabitant per square kilometer ( Greenland : 0.03 inhabitants / km 2,Western Sahara : 1 inhabitants / km 2).
The global density is 45 inhabitants / km.

Cities and the most densely populated

Country

Cities and towns

The cities with the highest population densities:

All these territories share a relatively small area and level of urbanization exceptionally high, with a population urban economically specialized utilizing agricultural resources outside, which illustrates the difference between a high population density and overpopulation .

States concerning a certain size, is the most densely populated Bangladesh , where 147 million people live in a highly agricultural area around the mouth of the Ganges , with a population density of over 1,000 inhabitants per km 2. Population density on total land area is at present of 42 inhabitants per km 2. The case of urban areas

Agglomerations with an unusually high population density are often seen as overcrowded, although this depends on many factors such as quality of housing and infrastructure or access to resources. The densest cities are located in the southern and eastern Asia , though Cairo and Lagos in Africa also fall into this category.

The population of a city, however, depends strongly on the definition used for the urban area: densities are higher if one considers only the center of the municipality unless there are also the suburbs - of more recent development and not yet incorporated administratively - as in the concepts of agglomeration or metropolitan area , the latter including some from neighboring towns. See also

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