The world's population is unlikely to continue growing rapidly and could peak within 70 years. The population decline could come even faster in regions such as Eastern Europe and in Russia west of the Urals, but one result will be a much greater number of older people.
There is an 85 per cent chance that the number of people on the planet will be on the way down before 2100, with a peak in that year of 8.4 billion, according to a new analysis published this morning in the journal Nature. This figure is about one billion short of the current United Nations prediction.
Dr Wolfgang Lutz of the International Institute for Applied Systems Analysis in Laxenburg, Austria, and colleagues used new methods of "probabilistic forecasting" to make their predictions. This allowed them to make percentage estimates of their accuracy.
They state, for example, that there is a 75 per cent chance that the peak population of the European portion of the former USSR has already been reached, at 236 million, with an 88 per cent probability that it will be reached by 2025. There is a better than 50/50 probability that China's population will level off by 2040 at a figure below 1.8 billion.
The numbers in Western Europe will fall from a high of 478 million in 2025 to 392 million by 2100, the group says. The North American picture is much different, however, with only that region and Latin America expecting unbroken population growth.
North America is predicted in the study to have a population of 454 million by 2100 while Latin America will have 934 million in that year. The researchers also predict that despite the prevalence of HIV infection in sub-Saharan Africa, population there is likely to double before it begins to decline after 2075.
The researchers expect the world population to peak at about 8.951 billion in 2075 and then to go into gentle decline. The authors warn, however, that "a stabilised or shrinking population will be a much older population".
The proportion of people over 60 is likely to increase from its current level of 10 per cent to about 22 per cent by 2050, they say.
"This is higher than it is in Western Europe today. By the end of the century it will increase to around 34 per cent and extensive population ageing will occur in all world regions."
Even sub-Saharan Africa is likely to be more aged than Europe is today, they add. "This confirms recent criticism that conventional projections tend to underestimate ageing." The change will pose "major social and economic challenges", the authors conclude.
