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Note: This article is from Conservation Magazine, the precursor to Anthropocene Magazine. The full 14-year Conservation Magazine archive is now available here.

The Depopulation Bomb

July 29, 2008

By Phillip Longman

When asked how long it will take for the world’s population to double, nearly half of all Americans say 20 years or less. This is hardly surprising, given the sensations of overcrowding we feel in our day-to-day lives and the reports of teeming Third World megacities. Yet looking beneath the surface, we see that world population growth has already slowed dramatically over the last generation and is headed on a course for absolute decline. Due to falling fertility rates, the world supply of children under four is already in decline; most remaining population growth will come from increases in the number of old people. Indeed, the United Nations shows that the world population growth rate could turn negative during the lifetime of people now in their 40s and 50s.

The global decline in fertility rates, as profound and well established as it may be, is hard to spot by observing the fabric of ordinary life. Indeed, ordinary life gives most people the opposite impression. That’s because even in areas where birthrates are dramatically below the levels required to avoid population loss, the absolute number of people is still growing.

If this seems counterintuitive, think of a train accelerating up a hill. If the engine stalls, the train will still move forward for a while, but its loss of momentum implies that it will soon be moving backwards, and at ever-greater speed. So it is when fertility rates shift from above to below replacement levels.

A falling population might at first seem beneficial to the environment. Yet as societies age, the cost of healthcare and pensions can consume resources that would otherwise be available for investment in cleaner energy and conservation. Falling population also erodes the market case for such investments by reducing the depletion rates and, therefore, the price of carbon-based forms of energy.

A world of 3 billion persons living in sprawling McMansions and driving SUVs will make more pollution than a world of 9 billion persons who have, out of necessity, learned to shun sprawl, eliminated auto dependency, and developed alternative, cleaner forms of energy. Japan is a world leader in energy efficiency and conservation precisely because its high population density and dependence on foreign oil make investments in energy-saving systems such as mass transit not only economically feasible but economically necessary.

A society in which childlessness is common and family size is small requires a large number of housing units per person. An aging society is likely to be risk adverse, less entrepreneurial, and less committed to education, making technological solutions to problems such as global warming less likely. Finally, with fewer workers to support each retiree and with each retiree consuming more and more healthcare, economies will have to run faster and harder to finance the burden.

1. Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat, World Population Prospects: The 2004 Revision and World Urbanization Prospects: The 2003 Revisio,. Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat, World Population Prospects DEMOBASE

Additional Reading
The Empty Cradle, by Phillip Longman, Basic Books, 2004.

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