Population rising with no end in sight!

Rising populations in Africa = more crowding. Could Africa be as dense as China in 2100?

Beijing 2010, Mauricio Pizard

If the world is seeming crowded, you ain’t seen nothing yet. While many estimates foresee population growth running aground long before 2100, a new study drowns that idea by projecting that 9.6 to 12.3 billion people will cohabit the third rock from the sun by 2100.

Current population is 7.26 billion, and rising fast.

If you think more is better, that’s good news. But you worry if you think population growth feeds shortages of fresh water, border wars, ethnic strife and environmental devastation. Can we feed, clothe, house and employ so many people on one planet?

A study published in Science Sept. 19 was grounded on the two main drivers of future population: life expectancy at birth and total fertility — the number of children born per woman over her lifetime. But study leader Adrian Raftery, a professor of statistics and sociology at the University of Washington, Seattle, employed them differently.

How much land for food?

The continuing decline of arable land per person bodes ill for feeding our growing population, especially considering water shortages, soil degradation, climate change and construction of roads, cities and houses.

Graph: Food and Agriculture Organization

Demographic agencies have traditionally asked experts to put numbers on future life expectancy and fertility. Instead, Raftery says, he and his colleagues at the United Nations Population Division performed a statistical analysis of historic rates in all countries over the last 60 years.

Then, in a multi-layer statistical exercise, they created thousands of future scenarios through 2100. The procedure was analogous to climate models, which can be run thousands of times to help assess the probability of each particular projection.

Up, up and away

The outcome was unmistakable: growth continues, especially in Africa (current population 1.2 billion), which has four chances in five of having a population between 3.5 and 5.1 billion in 2100. Raftery concedes these are “giant numbers… but if you project forward based on fertility and mortality, that’s what you get. It’s not unprecedented; it would give a population density in Africa that’s about the same as China now.”

Nigeria’s population, currently 160 million, is projected to reach 914 million.

Global population projected to 2100

Red shows median projection. The range of 95 percent probability is inside red dotted lines. Blue lines show a traditional projection technique that added or subtracted 0.5 child per woman from the central tendency. Projections are based on rates of fertility (see rollover) and life expectancy.

Credit (both): U.N. Department of Economic and Social Affairs

Health centers are scarce in Niger, West Africa. Here, women get information about the so-called “essential family practices,” such as breastfeeding, hygiene and birth spacing.

European Commission DG ECHO

We were skeptical that food-short Africa could survive such a dramatic increase, and Raftery told us his study did not explicitly consider war, famine or disease. Could Africa really survive with the density of China, a country that is buying land in Africa to feed its people?

We had trouble imagining African nations buying land abroad to feed themselves, but Raftery stuck by his analysis, maintaining that historic demographic data account for historic, real-world cataclysms.

Can I get a little support? No?

If its results are widely accepted, the new study may reignite concern about what was once called “the population bomb.” “Until the 1990s, population was a major global concern, then it fell off the world agenda, in favor of [matters like] HIV, climate change and terrorism,” says Raftery. “People felt it was a problem that was in the process of solving itself. These new results show that was premature; there’s a need to put the population issue back on the world agenda.”

ENLARGE

Retirees depend on support from working-age people. These projections were developed with the same techniques as those used for world population.

Graph adapted from U.N. Department of Economic and Social Affairs

All of this growth, Raftery says, “will obviously present environmental, health and social challenges for these countries going forward, which would be easier to deal with if the population grew less quickly.” Population feeds global warming, for example, as more people do the things that release greenhouse gases.

Aside from Africa, population growth will cease in most regions long before 2100, causing an inevitable decline in the ratio of working adults to retirees. Even Brazil, which now has almost nine workers per retiree, will only have 1.5 by century’s end, says Raftery. “That’s lower than Japan currently, and the same is true of India, China and Egypt. Countries we think of having young populations are going to face exactly the same problems with an aging population.”

In Europe, Japan and North America, the issue is already on the table; the rising age for full U.S. Social Security benefits is one attempt to ease the imbalance.

Some suggest growing more babies way to ensure a comfortable retirement, but that will not work forever, says Raftery. “In the end, high birth rates is a pyramid scheme. Eventually the basic issue becomes, if you are going to live to 90, you are going to spend a lot of time in retirement. If you are retired for 25 years, and spend 40 years working, you are not going to have many more workers for each retiree.”