Population density (in agriculture: standing stock and standing crop) is a measurement of population per unit area or unit volume; it is a quantity of type number density. It is frequently applied to living organisms, and most of the time to humans. It is a key geographical term.[1] In simple terms population density refers to the number of people living in an area per kilometer square.
Biological population densities
Population density is population divided by total land area or water volume, as appropriate.[1]
Low densities may cause an extinction vortex and lead to further reduced fertility. This is called the Allee effect after the scientist who identified it. Examples of the causes in low population densities include:[2]
Increased problems with locating sexual mates
Increased inbreeding
Monaco in Southern Europe, currently holds the record for being the most densely populated nation in the world.
Mongolia is the least densely populated country in the world.
This population cartogram of the European Union (2007–2012) uses areas and colors to represent population.
Main article: List of countries and territories by population density
For humans, population density is the number of people per unit of area, usually quoted per square kilometer or square mile (which may include or exclude, for example, areas of water or glaciers). Commonly this may be calculated for a county, city, country, another territory or the entire world.
The world's population is around 7,500,000,000[3] and Earth's total area (including land and water) is 510,000,000 square kilometers (197,000,000 sq. mi.).[4] Therefore, the worldwide human population density is around 7,500,000,000 ÷ 510,000,000 = 14.7 per km2 (38 per sq. mi). 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. mile). This includes all continental and island land area, including Antarctica. If Antarctica is also excluded, then population density rises to over 55 people per km2 (over 142 per sq. mile).[1] However, over half[citation needed] 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. Thus, this number by itself does not give any helpful measurement of human population density.
Several of the most densely populated territories in the world are city-states, microstates and dependencies.[5][6] These territories have a relatively small area and a 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
The potential to maintain the agricultural aspects of deserts is extremely limited as there is not enough precipitation to support a sustainable land. The population in these areas are extremely low. Therefore, cities in the Middle East, such as Dubai, have been increasing in population and infrastructure growth at a fast pace.[7]