Recently the media was abuzz with a story about how the 7 billionth person was just born on the planet followed by a UN report that the world’s population will grow to 10 or even 15 billion by the end of this century.

Now Der Spiegel brings us an entirely different perspective.  Some well-respected demographers disagree with the UN’s conclusions.  Indeed, they think the world’s population might actually start to decline by 2060 of 2070.  In a lengthy piece Der Spiegel examines the arguments in favour of a rapidly expanding population in our future and contrast that with arguments that the population will actually start to decline in most parts of the world except Pakistan, Afghanistan and the countries in sub-Saharan Africa.

An entire generation grew up in a world in which everything was on the increase, from the world’s population to mankind’s consumption of energy, food and land. Fears of a “population bomb” were reflected in the things we learned in school.

To a certain extent, the fears are justified. The global population will continue to grow for decades. “But,” says Wolfgang Lutz, “that shouldn’t distract us from the fact that an entirely different development has been underway for some time.” Lutz is the director of the Vienna-based International Institute for Applied System Analysis (IIASA) and one of the world’s most prominent demographers. As he sees it, it is “highly probable that mankind will begin to shrink by 2060 or 2070.”

It will be a global turning point. For the first time since the Black Death raged in the 14th century, the world’s death rate will be higher than its birth rate.

A boom in the number of births will be followed by a shrinking population in surprisingly quick succession. Someone in his mid-40s today has experienced the doubling of mankind in his lifetime and, if Lutz is right, he could also witness the first day of the Great Contraction.

Here is a graph that shows the different population trajectories for the UN and Lutz.

If Lutz is right, then the problems facing the world next century will be much different from what we now believe.

In addition to the old challenges, such as feeding the masses, there will also be new ones, such as caring for aging baby boomers. Instead of AIDS and malaria, medicine will be faced with the challenges of diabetes and dementia.

The UN prediction of a continually rising population is supported by three factors: First, life expectancy is on the rise, increasing statistically by three months each year. Second, child mortality is declining. And, finally, the children produced by the population boom are now reaching reproductive age.

The key element in all population models is simply how many children will the average woman give birth to.  And this is where Lutz and other demographers differ with the UN.   They believe that the number of births will start to decline and is, in fact. declining not only in the developed world but in many parts of the developing world as well.  Population growth is beginning to or will soon decline in Europe, Asia and South America.

Only Pakistan, Afghanistan and the countries in sub-Saharan Africa are still reporting significantly higher birth rates. Niger leads the pack with a particularly impressive rate of seven children per woman. Indeed, by the end of the century, Africa is expected to be home to more than 2 billion people. But the demographic pendulum is shifting even there, as women begin to have fewer children.

Demographers see societies moving thorough five phases of population transformation and as they approach that fifth phase their reproduction habits change markedly.  The article discusses each of these five phases and the root causes for each phase.  In that latter phase birth and death rates start to equalize and the population reaches a more or less stable equilibrium in an aging, urban environment.  Lutz thinks that number may be about 6 billion people. “That would put us within a range that environmentalists view as tolerable for our planet,” he says.

For those interested in the global population issue, the article is well worth reading.

See also The world at 7 billion? Not so fast in The Globe and Mail.