Everything about Population Growth totally explained
Population growth is the change in
population over time, and can be quantified as the change in the number of individuals in a population using "per unit time" for measurement. The term
population growth can technically refer to any species, but almost always refers to humans, and it's often used informally for the more specific
demographic term
population growth rate (see below), and is often used to refer specifically to the growth of the
population of the world.
Simple models of population growth include the
Malthusian Growth Model and the
logistic model.
Population growth rate
In demographics and
ecology,
Population growth rate (PGR) is the
fractional
rate at which the number of individuals in a population increases. Specifically, PGR ordinarily refers to the change in population over a specific time period expressed as a
percentage of the number of individuals in the population at the beginning of that period. This can be written as the formula:
A positive growth ratio (or rate) indicates that the population is increasing, while a negative growth ratio (or rate) indicates population decline. A growth ratio of zero indicates that there were the same number of people at the two times -- net difference between births, deaths and migration is zero. However, a growth rate may be zero even when there are significant changes in the birth rates, death rates, immigration rates, and age distribution between the two times.
A related measure is the
net reproduction rate. In the absence of migration, a net reproduction rate of more than one indicates that the population of women is increasing, while a net reproduction rate less than one (
sub-replacement fertility) indicates that the population of women is decreasing.
Human population growth rate
When population growth can exceed the
carrying capacity of an area or environment the results end with
overpopulation. Spikes in human population can cause problems such as
pollution and
traffic congestion, though these can be addressed by technological and economic changes. Conversely, such areas may be considered "underpopulated" if the population isn't large enough to maintain an
economic system (see
population decline).
Globally, the growth
rate of the
human population has slowed down a little since its peak in the 1980s (see External Links), although the last one hundred years have seen a rapid increase in population due to
medical advances and massive increase in agricultural productivity made by the
Green Revolution.
The actual annual growth in the number of humans fell from its peak of 87 million per annum in the late 1980s, to a low of 75 million per annum in 2002, at which it stabilised and has started to slowly rise again to 77 million per annum in 2007. Growth remains high in the
Middle East,
South Asia,
Southeast Asia,
Latin America, and primarily in
Sub-Saharan Africa.
In some countries there's
negative population growth (ie. net decrease in population over time), especially in
Central and
Eastern Europe (mainly due to low
fertility rates) and
Southern Africa (due to the high number of
HIV-related deaths). Within the next decade,
Japan and some countries in
Western Europe are also expected to encounter negative population growth due to
sub-replacement fertility rates.
Further Information
Get more info on 'Population Growth'.
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