I was born in 1957. Eisenhower was president. The Soviet Union launched Sputnik. The Cold War was heating up, even as McCarthyism literally died out. Science and technology were all the rage. Leonard Bernstein’s West Side Story debuted on Broadway. Leave It to Beaver with its vision of the ideal American family premiered on television.
There were 2.8 billion people alive on this planet in 1957 and 172 million of them were Americans. Sometime in 2011 demographers figure that the world reached 7 billion. That is two and a half times more people alive on the planet now than at the time of my birth. Here in the United States, the population is now at 312 million.
At the beginning of the Common Era (C.E.), the number of humans living on this planet was about 130 million distributed across the globe. Rome and Xi’an would have been the largest city in the world with an estimated population of 400,000. It would not be until 1800 that the world population reached 1 billion. In 1930 we reached 2 billion. Today we are at 7 billion. The largest city today is Tokyo with 32 million inhabitants. Seoul, Mexico City, and New York vie for the next largest with around 20 million. These numbers, and the sciences and societies behind them, are profoundly important to understanding the trajectory of humanity on its recent unprecedented growth spurt.
In 1968, a traumatic year on many accounts, a then 11-year old boy was further traumatized by reading Paul Ehrlich bestseller, The Population Bomb. Exponential growth curves merged in my young mind with images from the first televised mass starvation from the Nigerian-Biafran Civil War. The Population Bomb’s predictions were explosive. Fortunately the predictions were largely wrong.
It is important that we know in some detail how we got here and what scenarios might lie in store for the planet and its people over the next hundred years. Population growth is a factor of three trends: birthrates, life expectancy at birth, and the mortality or death rate. In my family, I was the fifth of six children, the tail end of the post World War II baby boomers. This was not unusual in the 1950s. The global fertility rates have since dropped from 5 to 2.5 children per woman. At the same time, life expectancy at birth has gone up and mortality rates have gone down. This is great news. Fewer children are born, they are less likely to die in childhood, and we tend to live longer lives. Our ability to cheat the Malthusian logic of limits goes primarily to three factors:
1) sanitation and civil engineering from which we derive clean drinking water and safe sewage disposal.
2) modern medicine, particularly vaccinations, through which we have dramatically reduced communicable diseases.
3) increased agricultural production through the use of hybrid crops, petrochemicals, irrigation, and industrialization at economies of scale in a now global food market.
Since the 1950s, life expectancy at birth around the world increased from about 47 years to 68 years. Here in North America, life expectancy is now about 78 years. Mortality rates are closely related to life expectancy, but significantly different in how they impact population age distributions and growth. How long you linger on this planet, when and how you die, for instance before or after reproduction, all end up impacting population growth. Longer-living humans are creating challenging demographic issues, for instance in increased pension payouts and skyrocketing health care costs for the lucky few. Of course at some point, mortality rates are 100 percent.
So what are our future prospects? Past performance is no guarantee of future success. Other than the certainty of death and taxes, we can predict that the world population will peak around 9 billion by 2050, a short 40 years hence. And if I live into my 90s, I may even see that day. From 7 billion to 9 billion people doesn’t seem like a big deal, but what it means in the larger context of Big History is that humanity must grow as much food over the next 40 years to feed itself as it has grown over the last 8,000 years since the rise of agriculture. Presumably we will have to do so with less waste, less water, fewer petrochemicals, less nitrogen, and less soil erosion. That would certainly be a Big Problem.
Population growth, however, is uneven. Seventy percent of the population growth in the next 40 years is predicted in extremely poor countries, while many of the rich countries are now stable or in decline. And more people are not simply a burden, they turn out to be a resource. More humans provide more labor, more productivity, and more creativity. Human numbers are thus engines of economic growth, not simply consumption. Counter-intuitively, some case studies around the world point to examples where increased population density results in reversals in ecological devastation.
And while the four horsemen—pestilence, famine, war, and death—always stand ready to reset our extravagant numbers, there are other reasons to be optimistic about the future. There are also new reasons for concern that would have been hard to anticipate 40 years ago.
Optimism arises from decreasing birth rates around the world. Education, health care, family planning, urbanization, and especially increased opportunities for adolescent girls and women are all highly correlated with lower fertility. Families are desiring and deciding to have fewer children. Increasingly they have the means and know-how to make those decisions. If fertility rates drop from 2.5 today down to 1.6 in the near future, then peak humanity will occur around 8 billion by 2025 and will actually decrease to 5 billion by 2100. Exponential patterns work going up and could also work coming down.
Environmentalists might applaud such a scenario—a planet at the turn of the next century with 2 billion fewer people than today—as it seems like fewer people would relieve some of the pressure on the planet’s ecosystems. The economic consequences of such a population decline, however, could be catastrophic in the short term. It is not clear that we can have economic growth with a declining population. If economies don’t grow, then paying off debt becomes an exponential burden unleashing a downward economic spiral. The collapse of our global economy is counter-intuitively also likely to be devastating for our global environment, as desperate people aren’t likely to care much about protecting the planet. And economic growth also helps drive the decisions of families to have fewer children. It seems we are in a triple-bind between containing population growth, protecting the environment, and growing economies. Big Problems!
The prospect of declining fertility also raises evolutionary concerns about the future of humanity on a soon to be child-scare planet. Children are literally the future of our species. Children humanize us. They inspire adults to be nurturing and future oriented. We need a planet with fewer children in a world that invests more in those few children, even though they may be someone else’s children. Fostering that kind of altruism and long-term commitment is a very Big Question.