By David Talbot
A new analysis suggests that the worldâ€™s population will keep rising through 2100, and not flatten around 2050 as has been widely assumed. Such an increase would have huge implications, but the predictionâ€™s reliability is debatable, given that it does not take into account future hardships a large population would likely face.
According to the new analysis by researchers at the United Nations and several academic institutions, there is an 80 percent chance that the worldâ€™s population, now 7.2 billion, wonâ€™t stop at nine billion in 2050, but will instead be between 9.6 billion and 12.3 billion by 2100. The researchers increased their estimates after noting persistent high birth rates and faster-than-expected progress in combatting HIV/AIDS in Africa, according to the study, which is published today in the journal Science.
There are significant caveats. Climate change is projected to put major stresses on agriculture and water supplies, and these stresses were not considered as potential checks on population growth. Nor does the study take into account that population growth could trigger deadly calamities like food shortages, war, and disease even without climate change, says John Bongaarts, vice president and distinguished scholar at the Population Council, a think tank and research organization based in New York City.
Past studies assumed that the pattern of declining birth rates observed in Asia and Latin America in recent decades would be repeated in Africa. This assumption is built into previous projections, notably ones of Wolfgang Lutz, director of the Vienna Institute of Demography.
But thatâ€™s not whatâ€™s actually happening. For example, in Nigeriaâ€”Africaâ€™s most populous nation, with 160 million residentsâ€”women are still having an average of six children each, as theyâ€™ve been doing for about the past 15 years. Such trends contribute to new estimates predicting a 90 percent probability that in 2100, Nigeriaâ€™s population will exceed 532 million. Africaâ€™s overall population is now expected to go from one billion to four billion, says Adrian Raftery, a professor of statistics and sociology at the University of Washington who coauthored the report.
Raftery also points out that United Nations estimates have a history of accuracy. Projections made in the 1950s held that the population in 2000 would be 6.2 billion, and would be around seven billion now, both of which are close to what actually happened.
In response to the study, Lutz says, his newest analysisÂ still suggestsÂ a less-dire outcome. â€œOur most likelyÂ scenario comes out somewhat lower than the current United Nations projections,â€ and suggests population willÂ peak at 9.4 billion around 2070 and start a slow decline to nine billion by the end of the century, he said in a statement.Â â€œThe end of world population growth is still to be expected this century.â€
The differences in the two projections, he said, is due to differingÂ methods and assumptions made about future birth and death rates for individual countries.
The United Nations paper offers prescriptions for keeping the population in check: more education for women and more widely available contraceptives.Î¦
David Talbot is MIT Technology Reviewâ€™s chief correspondent, interested in a wide range of topics including climate change, energy, and information and communication technologies. Recent projects have included traveling to China to write about GMO crop development there, and Germany to explore how theyâ€™ll try to ramp up renewable power while closing down nuclear plants. His 2008 feature on the Obama campaignâ€™s social-networking operation was selected for The Best Technology Writing 2009.