April 5, 2013
Physics Model Used To Track Global Population Stabilization By 2050
April Flowers for redOrbit.com - Your Universe Online
The population of our planet will stabilize around the middle of the next century, according to a research team led by the Autonomous University of Madrid (UAM).
Global population data from 1900 to 2010 enabled the team to make the prediction using a model normally used by physicists. Their results, published in the journal Simulation, coincide with the United Nation's (UN) downward forecasts.
The UN estimates that the global population in 2100 will be somewhere between the highest estimate of 15.8 billion (high fertility variant) and the lowest estimate of 6.2 billion (low fertility variant). The low estimate is below the current population of 7 billion.
The team of researchers from UAM and the CEU-San Pablo University developed a mathematical model that confirms the lower estimate. Additionally, their model predicts a standstill and even a slight drop in global population by the mid-21st century.
The UN provided population prospects between 1950 and 2100. The team combined these with mathematical equations used in fields such as condensed matter physics to create their model.
"This is a model that describes the evolution of a two-level system in which there is a probability of passing from one level to another," explained FÃ©lix F. MuÃ±oz, UAM researcher.
In their model, the Earth was considered as a closed and finite system. Human migration within the system had no impact and the fundamental principle of the conservation of mass, specifically biomass in this case, and energy is fulfilled.
"Within this general principle, the variables that limit the upper and lower zone of the system's two levels are the birth and mortality rates," MuÃ±oz pointed out, "recalling the change that occurred in the ratio between the two variables throughout the last century."
"We started with a general situation where both the birth rate and mortality rate were high, with slow growth favoring the former," he added, "but the mortality rate fell sharply in the second half of the 20th century as a result of advances in healthcare and increased life expectancy and it seemed that the population would grow a lot. However, the past three decades have also seen a steep drop-off in the number of children being born worldwide."
This situation is reflected in the model's S-shaped sigmoid curve with an inflection point in the mid-1980s. At this time, the speed at which the population is growing begins to slow down until it reaches a stable point around 2050.
The model's data also reflects the downward trend in the UN's series of prospects. "Overpopulation was a specter in the 1960s and 70s but historically the UN's low fertility variant forecasts have been fulfilled," MuÃ±oz highlighted.
Earlier predictions, as recently as 1992, predicted a global population of 7.17 billion people by 2010. The actual population in 2010 was 6.8 billion. There has been a 40 percent decline in the fertility rate since 1950.
"This work is another aspect to be taken into consideration in the debate, although we do not deal with the significant economic, demographic and political consequences that the stabilization and ageing of the world population could entail," the researcher concluded.