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Population density (in
agriculture Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary Image:Family watching television 1958.jpg, Exercise trends, Increases in sedentary behaviors su ...

agriculture
: standing stock or
plant density Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel t ...
) is a measurement of
population Population typically refers the number of people in a single area whether it be a city or town, region, country, or the world. Governments typically quantify the size of the resident population within their jurisdiction by a process called a ...

population
per unit area, or exceptionally unit volume; it is a quantity of type
number densityThe number density (symbol: ''n'' or ''ρ''N) is an intensive quantity used to describe the degree of concentration In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds ...
. It is frequently applied to
living organisms In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mecha ...
, most of the time to
human Humans (''Homo sapiens'') are the most abundant and widespread species In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes ...

human
s. 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.


Biological population densities

Population density is population divided by total land area or water volume, as appropriate. Low densities may cause an
extinction vortex Extinction vortices are a class of models through which conservation biologists, geneticists A geneticist is a biologist who studies genetics, the science of genes, heredity, and variation of organism In biology, an organism (from An ...
and lead to further reduced fertility. This is called the
Allee effectThe Allee effect is a phenomenon in biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiol ...
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 In biology, offspring are the young born of living organism, organisms, produced either by a single organism or, in the case of sexual reproduction, two organisms. Collective offspring may be known as ...


Human densities

Population density is the number of people per unit of area, usually quoted per square kilometre or square mile, and which may include or exclude for example areas of water or glaciers. Commonly this may be calculated for a
county A county is a geographical region of a country used for administrative or other purposesChambers Dictionary The ''Chambers Dictionary'' (''TCD'') was first published by William Chambers (publisher), William and Robert Chambers (publisher bo ...
,
city A city is a large human settlement.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 defined as a ...

city
,
country A country is a distinct territorial body or political entity A polity is an identifiable political entity—any group of people who have a collective identity, who are organized by some form of Institutionalisation, institutionalized social ...

country
, another
territory A territory is an administrative division Administrative division, administrative unitArticle 3(1). , country subdivision, administrative region, subnational entity, first-level subdivision, as well as many similar terms, are generic names ...
or the . The world's population is around 7,800,000,000 and
Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. The remaining 70.8% is Water distribution on Earth, covered wi ...

Earth
'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 per 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 per km2 (129 per sq. mi.). This includes all continental and island land area, including
Antarctica Antarctica ( or ) is Earth's southernmost continent. It contains the geographic South Pole and is situated in the Antarctic region of the Southern Hemisphere, almost entirely south of the Antarctic Circle, and is surrounded by the Southern Oc ...

Antarctica
. Furthermore, if Antarctica is also excluded, then population density rises to over 55 people per km2 (over 142 per sq. mi.). However, over half of the Earth's land mass consists of areas inhospitable to human habitation, such as deserts and high mountains, and population tends to cluster around seaports and fresh-water sources. Therefore, additional criteria are needed to make simple population density values meaningful and useful. Several of the most densely populated territories in the world are
city-state A city-state is an independent sovereign Sovereign is a title which can be applied to the highest leader in various categories. The word is borrowed from Old French Old French (, , ; Modern French French ( or ) is a Romance la ...
s,
microstate upright=1.4, Map of the smallest states in the world by land area. Note many of these are not considered microstates A microstate or ministate is a sovereign state A sovereign state is a political entity that is represented by one centralize ...
s 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 Urbanization (or urbanisation) refers to the population shift from rural File:Rural landscape in Finland.jpg, A rural landscape in Lappeenranta, South Karelia, Finland. 15 July 2000. In general, a rural area or a countryside is a geographi ...
level, with an economically specialized
city A city is a large human settlement.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 defined as a ...

city
population drawing also on rural resources outside the area, illustrating the difference between high population density and
overpopulation Overpopulation or overabundance occurs when a species' population In biology, a population is a number of all the organisms of the same group or species In biology, a species is the basic unit of biological classification, classifica ...
. 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, دبي, translit=Dubayy , ) is the most populous city in the United Arab Emirates The United Arab Emirates (UAE; ar, الإمارات العربية المتحدة ) or the Emirates ( ar, الإمارات ), is a country i ...

Dubai
, 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 or SEA, is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern subregion of Asia, consisting of the regions ...

Southeast Asia
); Africa's
Lagos Lagos (Nigerian English Nigerian English, also known as Nigerian Standard English, is a List of dialects of the English language, dialect of English spoken in Nigeria. Based on British English, the dialect contains various loanwords an ...

Lagos
,
Kinshasa Kinshasa (; ; ln, Kinsásá), formerly Léopoldville ( nl, Leopoldstad), is the capital Capital most commonly refers to: * Capital letter Letter case (or just case) is the distinction between the letters that are in larger uppercase ...

Kinshasa
and
Cairo Cairo ( ; ar, القاهرة, al-Qāhirah, , Coptic language, Coptic: ⲕⲁϩⲓⲣⲏ) is the Capital city, capital and List of cities and towns in Egypt, largest city of Egypt. The Greater Cairo, Cairo metropolitan area, with a population o ...

Cairo
; South America's
Bogotá Bogotá (, also , , ), officially Bogotá, Distrito Capital, abbreviated Bogotá, D.C., and formerly known as Santa Fe de Bogotá during the Spanish period and between 1991 and 2000, is the Capital city, capital and largest city of Colombia, a ...

Bogotá
,
Lima Lima ( ; ) is the capital and the largest city of Peru , , image_flag = Flag_of_Peru.svg , image_coat = Escudo_nacional_del_Perú.svg , other_symbol = Great Seal of the State , other_symbol_t ...

Lima
and
São Paulo São Paulo (, ; Portuguese for 'Saint Paul') is a city in the Southeast Region, Brazil, Southeast Region of Brazil. Listed by the Globalization and World Cities Research Network, GaWC as an global city, alpha global city, the Municipalities of ...

São Paulo
; and
Mexico City Mexico City ( es, link=no, Ciudad de México, ; abbreviated as CDMX; nah, Āltepētl Mēxihco) is the capital city, capital and largest city of Mexico, as well as the List of North American cities by population, most populous city in North Americ ...

Mexico City
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), ...

Saint Petersburg
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 centre 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 aggl ...
or
metropolitan area A metropolitan area or metro is a region consisting of a densely populated urban core Urban means "related to a city". In that sense, the term may refer to: * Urban area, geographical area distinct from rural areas * Urban culture, the cul ...

metropolitan area
(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 (United States), 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 i ...
's land area.


Countries and dependent territories


Other methods of measurement

Although arithmetic density is the most common way of measuring population density, several other methods have been developed to provide a more accurate measure of population density over a specific area. * Arithmetic density: The total number of people / area of land *
Physiological density The physiological density or real population density is the Population, number of people per unit area of arable land. A higher physiological density suggests that the available agricultural land is being used by more and may reach its output limit ...
: The total population / area of
arable land Arable land (from the la, arabilis, "able to be plough A plough or plow ( US; both ) is a farm tool for loosening or turning the soil before sowing seed or planting. Ploughs were traditionally drawn by oxen and horses, but in modern farms ...

arable land
* Agricultural density: The total ''rural'' population / area of
arable land Arable land (from the la, arabilis, "able to be plough A plough or plow ( US; both ) is a farm tool for loosening or turning the soil before sowing seed or planting. Ploughs were traditionally drawn by oxen and horses, but in modern farms ...

arable land
* Residential density: The number of people living in an urban area / area of residential land *
Urban density Urban density is a term used in urban planning Urban planning, also known as regional planning, town planning, city planning, or rural planning, is a technical and political process that is focused on the development and design A design is ...
: 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 *
Demography Demography (from prefix ''demo-'' from Ancient Greek Ancient Greek includes the forms of the used in and the from around 1500 BC to 300 BC. It is often roughly divided into the following periods: (), Dark Ages (), the period ...

Demography
*
Human geography Human geography or anthropogeography is the branch of geography Geography (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a coun ...
*
Idealised populationIn population genetics an idealised population is one that can be described using a number of simplifying assumptions. Models of idealised populations are either used to make a general point, or they are fit to data on real populations for which the ...
*
List of population concern organizations This is a list of organisations who promote a moderation of the size of the human population. Intergovernmental organizations Worldwide Regional Asia-Oceania * All countries – Asian Forum of Parliamentarians on Population and Development Th ...
* Optimum population *
Plant density Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel t ...
*
Population dynamics Population dynamics is the type of mathematics used to model and study the size and age composition of populations as dynamical systems. History Population dynamics has traditionally been the dominant branch of mathematical biology, which has a ...
*
Population genetics Population genetics is a subfield of that deals with genetic differences within and between s, and is a part of . Studies in this branch of examine such phenomena as , , and . Population genetics was a vital ingredient in the of the . Its pri ...
*
Population health Population health has been defined as "the health outcomes of a group of individuals, including the distribution of such outcomes within the group". It is an approach to health Health is a state of physical, mental and social well-being We ...
*
Population momentumPopulation momentum is a consequence of the demographic transition. Population momentum explains why a population In biology, a population is a number of all the organisms of the same group or species In biology, a species is the basic ...
*
Population pyramid A population pyramid or "age-sex pyramid" is a graphical illustration of the distribution of a population Population typically refers the number of people in a single area whether it be a city or town, region, country, or the world. Governme ...
* Rural transport problem *
Small population size Small may refer to: Science and technology * SMALL Small may refer to: Science and technology * SMALL, an ALGOL-like programming language * Small (anatomy), the lumbar region of the back * Small (journal), ''Small'' (journal), a nano-science pub ...


Lists of entities by population density

* List of Australian suburbs by population density *
List of countries by population density This is a list of countries and dependent territories ranked by population density, measured by the number of human Humans (''Homo sapiens'') are the most populous and widespread species of primates, characterized by bipedality, opposable thu ...
*
List of cities by population density This is a list of cities worldwide by population density. The population In biology, a population is a number of all the organisms of the same group or species In biology, a species is the basic unit of biological classification, cl ...
*
List of city districts by population density This is a list of the most Population density, densely populated Subdivision (land), city subdivisions (30,000+ inhabitants/km2) in the world with an area of at least 1 km2. Most are districts of large cities and may vary significantly in regi ...
*
List of English districts by population density This is a list of the districts of England The districts of England (also known as local authority districts or local government districts to distinguish from unofficial city districts) are a level of Subdivisions of England, subnational divis ...
*
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 The following is a list of islands, sorted by population density, and including islands that are connected to other land masses by a route other than sea or air, such as a bridge or a tunnel. Most densely populated islands (over 1,000 people per ...
* List of U.S. states by population density *
List of states and territories of the United States by population density 50 states, the 5 territories A territory is an administrative division, usually an area that is under the jurisdiction of a sovereign state. In most country, countries, a ''territory'' is an organized division of an area that is controlle ...


References


External links


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