The World in 2050_ Four Forces Shaping Civilization's Northern Future - Laurence C. Smith [6]
Arguments against Ehrlich’s ecological approach to human beings charged that it underestimated the limits of our technology and ingenuity. So far, these arguments appear to have been correct. Our numbers have surged on and Ehrlich’s scariest predictions have, as yet, failed to materialize. But even so, generations from now, our descendants will marvel at the twentieth century, a time when our numbers shot from 1.6 to 6.1 billion in a mere blink of time.
What triggered this enormous twentieth-century population spurt? Why did it not happen before, and is it likely to continue into the future?
Fast population growth behaves a lot like a personal savings account. Just as its account balance depends on the spread between the rates of deposit versus spending, the balance of people on Earth depends on the rates at which new people are created (the fertility rate) versus how fast existing people disappear (the death rate).15 When the two rates are equal, population holds steady. When they diverge or converge, population rises or falls accordingly. It doesn’t really matter whether birth rates rise or death rates fall; what matters is the spread and whether rate adjustments are staggered in time or happen simultaneously. Most importantly, once a run-up (or decline) has happened, we are stuck with the new population level, even if the gap between fertility and death rates is then closed and population stability is returned.
From our earliest beginnings until the late nineteenth century, our fertility and death rates, on average, were both high. Mothers had more babies than today, but few of them survived to old age. In the preindustrial era, famine, warfare, and poor health kept death rates high, largely offsetting high fertility. The global population of humans trickled higher, but only very slowly.
However, by the late nineteenth century, industrialization had changed everything in Western Europe, North America, and Japan. Mechanized food production and distribution reduced famine deaths. Local warfare disappeared under the rising control of central governments. Death rates dropped as doctors discovered modern medical procedures and drugs. But fertility rates fell more slowly—cultural expectations are slower to change—so the human population took off. By 1950, New York was the first city in the world to break the ten million mark.
Not only did the Industrial Age bring machines and medicine, it also spurred migration from farms to cities. People increasingly bought what they needed rather than growing or making things themselves. The cost of housing rose; the economy grew. More women entered college and the workplace, squeezing down the number of children families wanted or could afford. Fertility rates began to drop and families became smaller. When fertility rates at last fell to match the death rates, population growth halted, and the industrialized societies that had participated in all this were transformed. Instead of being small, poor, prolific, and death-prone they were now large, rich, and long-lived with few children.
This chain of events, in which a population run-up is at first initiated, then later stabilized, by the forces of modernization is called the Demographic Transition and is a bedrock concept in demography.16 The Demographic Transition supposes that modernization tends to reduce death and fertility rates, but not simultaneously. Because people tend to readily adopt technological advances in medicine and food production, death rates fall first and quickly. But fertility reductions—which tend to be driven by increased education and empowerment of women, an urban lifestyle,