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Study: Earth to host 11 billion people by end of century

"There is an 80 percent probability that world population, now 7.2 billion, will increase to between 9.6 and 12.3 billion in 2100," the study's authors write.

By Brooks Hays
Indians walk through a bazaar in New Delhi, India, a country expected to be the most populous in the world by 2075. (UPI Photo/Mohammad Kheirkhah)
Indians walk through a bazaar in New Delhi, India, a country expected to be the most populous in the world by 2075. (UPI Photo/Mohammad Kheirkhah) | License Photo

NEW YORK, Sept. 19 (UPI) -- World citizens be warned: if new projections are correct, there's going be a lot less elbow room by the end of the century. That's because there are going to be a lot more people around -- upwards of 12 billion of them, according to the latest population projections from scientists with the United Nations Population Division.

According to the new study -- published this week in the journal Science -- population growth is not likely to plateau in the second half of the 21st century. Instead, a new probabilistic model using recent trends suggests growth will continue through the end of the century.

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"There is an 80 percent probability that world population, now 7.2 billion, will increase to between 9.6 and 12.3 billion in 2100," the study's authors write. "Much of the increase is expected to happen in Africa, in part due to higher fertility and a recent slowdown in the pace of fertility decline."

"These are not predictions," demographer and lead author, John Wilmoth, told National Geographic. "These are projections of what will happen if current trends continue. There is still an opportunity to intervene."

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But not everyone in the field is on board with the new projections. Another study -- published earlier this summer in the journal Global Environmental Change -- remains more in line with previous U.N. projections, putting the world population closer to 9 billion by 2100. The study was carried out by Wolfgang Lutz and his fellow researchers at the International Institute for Applied Systems Analysis (IIASA) in Vienna, Austria. Lutz's team uses a different methodology, one which sources the projections of expert demographers all over the world -- each providing special knowledge of different regions -- and compiles them to create a macro model.

Both projections have India becoming the most populous country in the world by 2075, and both agree that China's growth will trail off by 2100. The main region where Lutz's projections differ from the U.N.' is in sub-Saharan Africa. Both expect population growth there to be significant -- but the U.N. slightly more so. Lutz says ongoing education efforts are likely to depress fertility rates in Africa.

But the former head of the U.N. Population Division, Hania Zlotnik, says such assumptions are misguided and distract from the necessity of intervention policies -- like the distribution of contraception.

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"No one knows, neither he nor us, what's going to happen," Zlotnik told National Geographic. "In order to get to a different future, you have to change the now."

"The important message is that governments need to react to the realities of population change," Wilmoth concurred. "At an individual level, women need access to family planning, and they need education. This study is a reminder of the importance of emphasizing both of these as we move forward."

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