population density - Biological population densities, Human population density, Other methods of measuring population density

A measure of the number of people living within a standard unit of area, useful for comparative purposes. For example, the population density of The Netherlands (2001) was 38

5 per km²/996 per sq mi, and for Australia (2001) 5 per km²/ 5 per sq mi. However, these are crude measurements, and take no account of the area of habitable land. Accordingly, population density may be calculated to relate population to cultivable land or some other economic indicator.

Population density is a measurement of population per unit area or unit volume.

Biological population densities

Population density is a common biological measurement and is often used by conservationists as a more appropriate measure than population size.

Human population density

For humans, population density is the number of persons per unit of area (which may include or exclude cultivated or potentially productive area).

The world population is 6.5 billion humans, and Earth's area is 510 million square kilometers (200 million square miles). Therefore the world-wide human population density is 6.5 billion / 510 million = 13 per km² (33 per sq mi), or 43 per km² (112 per sq mi) considering that humans live on land, which forms 150 million km² (58 million sq mi) of the earth. These territories share a relatively small area and an exceptionally high urbanization level, with an economically specialized city population drawing also on rural resources outside the area, illustrating the difference between high population density and overpopulation.

Cities with exceptionally high population densities are often considered to be overpopulated, though the extent to which this is the case depends on factors like quality of housing and infrastructure or access to resources. City population is however, heavily dependent on the definition used for the urban area: densities will be far higher for the central municipality than when more recently-developed and as yet administratively unincorporated suburbs are included, as in the concepts of agglomeration or metropolitan area, the latter including sometimes neighbouring cities.

Other methods of measuring population density

While the arithmetic density is the most common way of measuring population density, several other methods have been developed which aim to provide a more accurate measure of population density over a specific area.

Physiological density – The total population divided by the amount of arable land.

Agricultural density – The total rural population to the amount of agricultural land.

Ecological optimum – The density of population which can be supported by the area's natural resources.