Outgrowing the Earth: The Food Security Challenge in an Age of Falling Water Tables and Rising Temperatures


Lester R. Brown

Chapter 2. Stopping at Seven Billion: The Demographic Transition

In 1945, Princeton demographer Frank Notestein outlined a three-stage demographic model to illustrate the dynamics of population growth as societies modernized. (See Figure 2–2.) He pointed out that in pre-modern societies, births and deaths are both high and essentially in balance with little or no population growth. In stage two, as living standards rise and health care conditions improve, death rates begin to decline. With birth rates remaining high while death rates are declining, population growth accelerates, typically reaching 3 percent a year. Although this may not sound like much, 3 percent a year results in a twentyfold increase per century. As living standards continue to improve, and particularly as women are educated, the birth rate also begins to decline. Eventually the birth rate drops to the level of the death rate. This is stage three, where population is again stable. 20

Of the 180 countries in the world today, some 36, with a combined population of 700 million people, have made it to stage three. With births and deaths essentially in balance, they have reached population stability. This leaves more than 140 countries—and 5.6 billion people—in stage two. Many with rising incomes and steadily declining birth rates are moving toward the population stability of stage three. Among them are China, Thailand, South Korea, and Iran. But many others in this group are not doing as well. After two generations of rapid growth, progress has largely come to a standstill. Living conditions in these largely rural societies are either improving very little or are deteriorating as family plots, divided and then subdivided, have left many families with too little land to sustain them. 21

Stage two of the demographic transition, particularly the early part, is a politically risky place for countries to be. A study by Population Action International, The Security Demographic: Population and Civil Conflict After the Cold War, surveys the work of social analysts searching for advance indicators of political instability. One of the better known of these initiatives, a group known as the State Failure Task Force and set up by the Central Intelligence Agency in the 1990s, tried to determine what social, political, economic, and environmental variables could help anticipate what they termed “state failure.” This, in effect, is a form of social disintegration, a collapse of order in a society. Of all the indicators analyzed by the task force, high infant mortality correlated most closely with political instability. 22

The second best indicator of political volatility was a disproportionately large share of the population in the young adult category, those in their late teens and twenties. The prospect that large numbers of young adults would foster social conflict and political instability was much stronger in societies where educational and economic opportunities were lacking. 23

Once countries have moved into the final stage of the demographic transition, when both mortality and fertility are low and essentially in balance, the chance of civil conflicts diminishes sharply. This suggests that it is in the global interest to help those countries that are stalled in stage two to get moving and make it into stage three as soon as possible.

The progression through stage two of the demographic transition is not a smooth one and it is by no means automatic. While there is no evidence of a country that has made it to stage three falling back into stage two, there is growing evidence that countries remaining in stage two for an inordinate amount of time are falling back into stage one. 24

Governments in countries that have experienced rapid population growth for nearly two generations are showing signs of “demographic fatigue.” Worn down by the struggle to feed, clothe, educate, and provide health care for an ever-expanding population, they are unable to respond to new threats, such as HIV/AIDS. 25

Countries that remain in stage two, with its rapid population growth, risk being overwhelmed by land hunger, water shortages, disease, civil conflict, and other adverse effects of prolonged rapid population growth. Yemen, Ethiopia, the Democratic Republic of the Congo, Somalia, and Afghanistan all fall into this category. Among the countries that are sliding back into stage one—where high death rates offset high birth rates, thus preventing any population growth—are Botswana and South Africa. 26

Within the next two decades or so, most of the countries in stage two will either have made it into stage three or fallen back to stage one. What is not clear is exactly what combination of events and forces will push countries backward demographically. At this point, it is obvious that the HIV epidemic is responsible for the handful of countries that are moving back toward stage one, where rising mortality may not merely balance fertility but exceed it, leading to an absolute decline in population. Countries where a fifth or more of adults are HIV-positive will lose a comparable share of their adult populations within the next decade or so. For each adult sick with AIDS, another adult typically provides care. As the virus spreads, the number of people able to till the fields shrinks, until eventually food production falls. At this point, disease and hunger reinforce each other in a downward spiral leading countries into a demographic dark hole. 27

*Data and additional resources have been omitted from this mobile version of our website to ensure the most optimal experience. To view this page with its entire information, please visit the full website.