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Population density (in
agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people ...
: standing stock or
plant density Plant density is the number of individual plants present per unit of ground area. It is most easily interpreted in the case of monospecific stands, where all plants belong to the same species and have germinated at the same time. However, it could ...
) is a measurement of
population Population typically refers to the number of people in a single area, whether it be a city or town, region, country, continent, or the world. Governments typically quantify the size of the resident population within their jurisdiction usi ...
per unit land area. It is mostly applied to humans, but sometimes to other living
organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells ( cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and fu ...
s too. It is a key geographical term.Matt Rosenber
Population Density
Geography.about.com. March 2, 2011. Retrieved on December 10, 2011.
In simple terms, population density refers to the number of people living in an area per square kilometre, or other unit of land area.


Biological population densities

Population density is population divided by total land area, sometimes including seas and oceans, as appropriate. Low densities may cause an
extinction vortex Extinction vortices are a class of models through which conservation biologists, geneticists and ecologists can understand the dynamics of and categorize extinctions in the context of their causes. This model shows the events that ultimately l ...
and further reduce fertility. This is called the Allee effect after the scientist who identified it. Examples of the causes of reduced fertility in low population densities are * Increased problems with locating sexual mates * Increased
inbreeding Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically. By analogy, the term is used in human reproduction, but more commonly refers to the genetic disorders a ...

Human densities

Population density is the number of people per unit of area, usually transcribed as "per square kilometer" or square mile, and which may include or exclude, for example, areas of water or glaciers. Commonly this is calculated for a
county A county is a geographic region of a country used for administrative or other purposes Chambers Dictionary, L. Brookes (ed.), 2005, Chambers Harrap Publishers Ltd, Edinburgh in certain modern nations. The term is derived from the Old French ...
,
city A city is a human settlement of notable size.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Science Encyclopedia''. 2nd edition. London: Routledge. It can be def ...
,
country A country is a distinct part of the world, such as a state, nation, or other political entity. It may be a sovereign state or make up one part of a larger state. For example, the country of Japan is an independent, sovereign state, whi ...
, another territory or the entire world. The world's population is around 8,000,000,000 and the
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...
's total area (including land and water) is 510,000,000 km2 (197,000,000 sq. mi.). Therefore, from this very crude type of calculation, the worldwide human population density is approximately 7,800,000,000 ÷ 510,000,000 = 15.3/km2 (40 per sq. mi.). However, if only the Earth's land area of 150,000,000 km2 (58,000,000 sq. mi.) is taken into account, then human population density is 50/km2 (129 per sq. mi.). This includes all continental and island land area, including
Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...
. But if Antarctica is excluded, then population density rises to over 55 persons/km2 (over 142 per sq. mi.). Several of the most densely populated territories in the world are
city-state A city-state is an independent sovereign city which serves as the center of political, economic, and cultural life over its contiguous territory. They have existed in many parts of the world since the dawn of history, including cities such as ...
s, microstates and urban dependencies. In fact, 95% of the world's population is concentrated on just 10% of the world's land. These territories have a relatively small area and a high urbanization level, with an economically specialized
city A city is a human settlement of notable size.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Science Encyclopedia''. 2nd edition. London: Routledge. It can be def ...
population drawing also on rural resources outside the area, illustrating the difference between high population density and
overpopulation Overpopulation or overabundance is a phenomenon in which a species' population becomes larger than the carrying capacity of its environment. This may be caused by increased birth rates, lowered mortality rates, reduced predation or large scale ...
. Deserts have very limited potential for growing crops as there is not enough rain to support them. Thus, their population density is generally low. However, some cities in the Middle East, such as
Dubai Dubai (, ; ar, wikt:دبي, دبي, translit=Dubayy, , ) is the List of cities in the United Arab Emirates#Major cities, most populous city in the United Arab Emirates (UAE) and the capital of the Emirate of Dubai, the most populated of the 7 ...
, have been increasing in population and infrastructure growth at a fast pace.Cities with high population densities are, by some, considered to be overpopulated, though this will depend on factors like quality of housing and infrastructure and access to resources. Very densely populated cities are mostly in Asia (particularly
Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainland ...
); Africa's
Lagos Lagos (Nigerian English: ; ) is the largest city in Nigeria and the second most populous city in Africa, with a population of 15.4 million as of 2015 within the city proper. Lagos was the national capital of Nigeria until December 1991 fo ...
, Kinshasa, and Cairo; South America's Bogotá, Lima, and
São Paulo São Paulo (, ; Portuguese for ' Saint Paul') is the most populous city in Brazil, and is the capital of the state of São Paulo, the most populous and wealthiest Brazilian state, located in the country's Southeast Region. Listed by the GaW ...
; and
Mexico City Mexico City ( es, link=no, Ciudad de México, ; abbr.: CDMX; Nahuatl: ''Altepetl Mexico'') is the capital and largest city of Mexico, and the most populous city in North America. One of the world's alpha cities, it is located in the Valley o ...
and
Saint Petersburg Saint Petersburg ( rus, links=no, Санкт-Петербург, a=Ru-Sankt Peterburg Leningrad Petrograd Piter.ogg, r=Sankt-Peterburg, p=ˈsankt pʲɪtʲɪrˈburk), formerly known as Petrograd (1914–1924) and later Leningrad (1924–1991), i ...
also fall into this category.City population and especially area are, however, heavily dependent on the definition of "urban area" used: densities are almost invariably higher for the center only than when suburban settlements and intervening rural areas are included, as in the
agglomeration Agglomeration may refer to: * Urban agglomeration, in standard English * Megalopolis, in Chinese English, as defined in China's ''Standard for basic terminology of urban planning'' (GB/T 50280—98). Also known as " city cluster". * Economies of ag ...
or
metropolitan area A metropolitan area or metro is a region that consists of a densely populated urban agglomeration and its surrounding territories sharing industries, commercial areas, transport network, infrastructures and housing. A metro area usually ...
(the latter sometimes including neighboring cities). In comparison, based on a world population of 7.8 billion, the world's inhabitants, if conceptualized as a loose crowd occupying just under 1 m2 (10 sq. ft) per person (cf. Jacobs Method), would occupy a space a little larger than
Delaware Delaware ( ) is a state in the Mid-Atlantic region of the United States, bordering Maryland to its south and west; Pennsylvania to its north; and New Jersey and the Atlantic Ocean to its east. The state takes its name from the adjacent ...
's land area.


Countries and dependent territories


Other methods of measurement

Although the arithmetic density is the most common way of measuring population density, several other methods have been developed to provide alternative measures of population density over a specific area. * Arithmetic density: The total number of people / area of land * Physiological density: The total population / area of
arable land Arable land (from the la, arabilis, "able to be ploughed") is any land capable of being ploughed and used to grow crops.''Oxford English Dictionary'', "arable, ''adj''. and ''n.''" Oxford University Press (Oxford), 2013. Alternatively, for th ...
* Agricultural density: The total ''rural'' population / area of
arable land Arable land (from the la, arabilis, "able to be ploughed") is any land capable of being ploughed and used to grow crops.''Oxford English Dictionary'', "arable, ''adj''. and ''n.''" Oxford University Press (Oxford), 2013. Alternatively, for th ...
* Residential density: The number of people living in an urban area / area of residential land * Urban density: The number of people inhabiting an urban area / total area of urban land * Ecological optimum: The density of population that can be supported by the natural resources * Living density: Population density at which the average person livesAnalysis of living population density per countries
based on NASA SEDAC world gridded data.


See also

*
Distance sampling Distance sampling is a widely used group of closely related methods for estimating the density and/or abundance of populations. The main methods are based on line transects or point transects.Buckland, S. T., Anderson, D. R., Burnham, K. P. and La ...
* Demography *
Human geography Human geography or anthropogeography is the branch of geography that studies spatial relationships between human communities, cultures, economies, and their interactions with the environment. It analyzes spatial interdependencies between social ...
* Idealised population * List of population concern organizations *
Plant density Plant density is the number of individual plants present per unit of ground area. It is most easily interpreted in the case of monospecific stands, where all plants belong to the same species and have germinated at the same time. However, it could ...
* Population dynamics * Population decline * Population growth * Population genetics * Population health *
Population momentum Population momentum is a consequence of the demographic transition. Population momentum explains why a population will continue to grow even if the fertility rate declines. Population momentum occurs because it is not only the number of children ...
* Population pyramid * Rural transport problem * Small population size


Lists of entities by population density

* List of Australian suburbs by population density * List of countries by population density *
List of cities by population density This is a list of cities worldwide by population density. The population, population density and land area for the cities listed are based on the entire city proper A city proper is the geographical area contained within city limits. The t ...
* List of city districts by population density *
List of English districts by population density This is a list of the districts of England ordered by population density, based on population estimates for from the Office for National Statistics. The densities are calculated by dividing the latest Population Estimate by the Standard Area Mea ...
*
List of European Union cities proper by population density The population, population density, and land area for the cities of the European Union listed below are based on the entire city proper, the defined boundary or border of a city or the city limits of the city. See also *List of cities by popu ...
* List of islands by population density * List of states and territories of the United States by population density


References


External links


Selected Current and Historic City, Ward & Neighborhood Density
* {{DEFAULTSORT:Population Density Environmental controversies Geography Human overpopulation Population ecology Demography