Contrary to previous estimates, the number of people on the planet now seems unlikely to stabilize this century
Sep 19, 2014 |By David Biello
In the 1970s, the world reached peak child—the highest rate of human population growth. Since then, countries in Asia, the Americas, Australia and Europe have all seen birth rates decline dramatically and in Africa, the number of children in families has dropped from an average of more than six to around four. But that decline in Africa is slower than the birth rate drops in other parts of the world. The persistence of that relatively high birth rate stems from a wide range of factors, including cultural influences, economics, and a lack of access to birth control or family planning. And there are enough children in Africa now that some demographers and statisticians are predicting that human population growth will not actually flatten in the 21st century, as some experts had foretold.
Other recent estimates have forecast a leveling out of human population growth by mid-century, from a current 7.2 billion people to around 10 billion by 2050. But those projections counted on families in Africa reducing the number of children they have at roughly the same rate that fertility declined in Asia and Latin America in previous decades. Instead, women are still having more children in many African countries and the rate of fertility decline has slowed—or even reversed—in some African countries in the last 15 years. “This has a compounding effect on population over time, because higher fertility means more children for the current population, and hence more grandchildren and so on,” explains statistician Adrian Raftery of the University of Washington, part of the team that conducted the new analysis. “We project a large increase in the population of Africa, from the current 1 billion to 4.2 billion in 2100,” he notes. Raftery and his colleagues detail their findings in a report published online September 18 in Science.
How fast and how far fertility in Africa falls—or doesn’t—will determine the fate of human population growth or decline this century. At current rates, the African continent would likely become as densely populated as China today. As a result, the “world population is likely to continue growing for the rest of the century,” Raftery says, although fast population growth in Africa may also lead to the kind of shortages of food, water and other resources that can reduce population growth.
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