It is wildly irresponsible and premature to declare — as some commentators have, including John Ibbitson recently in these pages — that the human population explosion is over and that we should begin worrying about a global “birth dearth” or “population implosion.” These commentators have misinterpreted, and taken out of context, recent data on fertility trends from around the world. Yes, these data show that we may have turned the corner on the population explosion. But no, the problem of population growth isn’t behind us yet.
First, some background. During the twentieth century the world’s population nearly quadrupled, from 1.65 to around six billion people. Never before have our numbers increased so fast in absolute terms. In 1900, the annual growth of our population was about ten million people; at the beginning of the twenty-first century, it is just under eighty million (it peaked in the late 1980s at 87 million).
Yet beyond our vague intuition that six billion is a very large number, most of us can’t really grasp this statistic’s true meaning. Imagine this population evenly distributed across the planet’s sixty million square kilometers of habitable land — across Earth’s prairies, rangelands, farms, and urban landscapes; across its coastal plains, terraced hillsides, and temperate forests. Spread out this way, each of us would nevertheless remain within easy calling distance of our neighbors: we would be dotted across the landscape barely one hundred meters from each other.
The world has become a crowded place. But population growth will not last forever. In fact, it’s already ending, as John Ibbitson rightly pointed out. In the last two decades, education, economic development, and modern ideas have spread and the status of women has improved in poor countries. In tandem, the average number of babies born to each woman (what demographers refer to as the fertility rate) has fallen very fast — indeed, much faster than even the most optimistic demographers predicted.
Countries like Thailand, Bangladesh, and Kenya, where women used to have an average of six or more children, have seen that number drop to three and, in some cases, even two. Meanwhile, in many rich countries, especially in Europe, fertility rates have fallen far below the 2.1 births per woman required to replace the population, posing major challenges for economic and social policy.
So, doesn’t this mean that the population explosion is over. No, it doesn’t. The 2001 United Nations’ “medium” projection says that world population will still grow by more than 50 percent — from the current 6.1 billion to 9.3 billion by 2050. This figure is nearly half of billion more than the organization suggested in its 1998 medium projection. The U.N.’s demographers made this upward revision because, it turns out, fertility rates in some of the world’s most populous countries — including India, Nigeria, and Bangladesh – aren’t falling as quickly as thought.
The world’s total population will grow by about 720 million people — more than 20 times Canada’s population — in each of the next two decades (2000-2010 and 2010-2020). About 95 percent of this increase will occur in poor countries. Moreover, around fifty percent of poor countries’ growth, in turn, will result from sheer “demographic momentum.” The large number of girls still to reach reproductive age — girls born during the 1980s and 1990s when the biggest annual increments were added to the world’s population — guarantees further population growth even if the best family planning technologies are widely available, which usually they are not.
Many countries’ underlying populations are now so large that even small annual growth rates, in percentage terms, still mean large increments in total population. Although India’s growth rate is now under two percent per year and China’s is under one percent, their respective populations still grow by fifteen and ten million people every year. We should also not forget that the drop in birth rates has not happened to the same degree in all poor countries. In some, birth rates remain very high: At least seventy-four countries — including Nigeria, Syria, and Honduras — will likely double their populations in the next two or three decades.
But does this really matter? Don’t larger populations provide more labor to produce goods and services, bigger markets to buy those goods and services, and more heads to generate useful ingenuity?
Sometimes large populations can be a boon. But too often, in combination with inefficient, incompetent, or corrupt markets and governments, population growth means less investment per child in nutrition, medicine, and education; a diversion of a society’s wealth from saving and investment to consumption; and the division of vital family resources – such as a family’s plot of cropland — into smaller and smaller parcels as it is passed to each successive generation of children.
When European populations grew rapidly in the nineteenth and early twentieth centuries, many people who didn’t have enough land or who couldn’t find good jobs emigrated to the Americas and to colonies in Africa and Asia. But a similar escape valve is, for the most part, no longer available to today’s poor countries, and their extra population must be largely absorbed and employed at home.
Many of these people move into megacities such as Karachi in Pakistan. Water systems, roads, electrical grids, sewers, and other essential infrastructures of daily life are severely overtaxed. The political instability of these cities is magnified by their populations’ “youth bulge.” In Africa, for example, over 40 percent of the population is under fifteen years old. Underemployed, urbanized young men are an especially volatile group that can be easily entrapped in organized crime or mobilized for violent political action, like terrorism.
Perhaps most importantly, larger human populations usually place a greater burden on the natural environment that surrounds them — including the planet’s climate, its fisheries, and its supplies of fresh water, cropland, and forests. In places like China, India, Pakistan, and Egypt, these resources are already extraordinarily stressed and can’t possibly sustain their countries’ enormous populations indefinitely.
The human population explosion is far from over, and its dire effects will be with us for many decades yet. “As many people will be added in the next 50 years as were added in the past 40 years,” the U.N. writes, “and the increase will be concentrated in the world’s poorest countries, which are already straining to provide basic social services to their people.”