Earth’s population bomb is fizzling
For more than two centuries, thoughtful people have been worrying that rising populations would overtax the world’s resources. “The power of population is so superior to the power of the earth to produce subsistence for man, that premature death must in some shape or other visit the human race,” English clergyman Thomas Robert Malthus wrote in “Essay on the Principle of Population” in 1798. A hundred and seventy years later, Stanford University biologist Paul Ehrlich argued pretty much the same thing in The Population Bomb:
“Each year food production in undeveloped countries falls a bit further behind burgeoning population growth, and people go to bed a little bit hungrier,” Ehrlich wrote. “While there are temporary or local reversals of this trend, it now seems inevitable that it will continue to its logical conclusion: mass starvation.”
Malthus and Ehrlich were both right that population growth was accelerating. England’s population doubled in the half century after 1798; the world’s population doubled from 3.5 billion in 1968 to 7 billion in 2011, just six years later than Ehrlich had predicted.
Mass starvation did not follow in either case, though, thanks to advances in agricultural productivity and world trade. This turn of events has done much to discredit the arguments of Malthus and Ehrlich. So have the solutions they proposed to population growth: Malthus opposed aid to the poor on the grounds that it would just encourage them to have more kids; Ehrlich pushed for population-control measures ranging from luxury taxes on diapers to forced sterilization.
Lately matters have taken an interesting turn. The population bomb is giving indications of fizzling. Yet concerns that we humans are overtaxing the environment seem to be growing.
On May 6, for example, a United Nations scientific panel issued a new report documenting that plant and animal species around the world are
going extinct at an accelerating rate. A key cause, according to the report, is that “in the past 50 years, the human population has doubled, the global economy has grown nearly four-fold, and global trade has grown 10-fold, together driving up the demands for energy and materials.”
Last week I also happened to finish reading Empty Planet: The Shock
of Global Population Decline, a book published early this year that extrapolates from current fertility trends to argue that the biggest challenges facing the world in the second half of the current century will have to do with falling population.
The authors, pollster Darrell Bricker and journalist John Ibbitson (both Canadians), are mainly interested in the impact on economic growth, politics, social relations and international affairs. But when they do discuss environmental matters, they are awfully sanguine about them.
“It will be cleaner, safer, quieter,” they write of the post-peak-population earth. “The oceans will start to heal and the atmosphere cool, or at least stop heating.”
So … problem solved, right? Not exactly.
Bricker and Ibbitson’s forecast of a coming population decline is not grabbed out of thin air. In affluent countries and a lot of not-so-affluent ones, population growth is slowing and in some cases going into reverse, thanks to fertility rates that have fallen below the 2.1 births per woman that keeps population steady over time. Worldwide, the fertility rate is now an estimated 2.4 births per woman, less than half what it was when Ehrlich issued his warning in 1968, and falling.
It is not falling evenly. This lends drama to Bricker and Ibbitson’s book, which envisions a shrinking China, a troubled Europe and, thanks to immigration, continued U.S. strength and a rising profile for Canada. Europe, East Asia and North America have had below-replacement fertility rates for decades now. Latin America recently joined this club, and the Middle East and South Asia seem inexorably headed for membership.
The one big outlier has been sub-Saharan Africa, where the fertility rate was still 4.8 in 2017 and hasn’t been falling as fast as some experts expected. Those experts may have had unrealistic expectations, though, and Bricker and Ibbitson figure that the same logic of urbanization and education that has driven steep birthrate declines elsewhere will apply in more and more African countries in the coming years.
Below-replacement fertility rates don’t immediately translate into population declines. Lengthening lifespans work against that, and if a country has a large enough cohort of young people, even with smaller families their kids will keep driving population higher for a while. The United Nations’ “medium variant” population projection from 2017 assumes that the global fertility rate will drop below replacement by 2070, but that world population will keep growing through the end of the century.
Still, past U.N. projections have consistently overshot (not by a huge amount), and one can’t really fault Bricker and Ibbitson for choosing instead to go with the projections of Austria’s Wittgenstein Centre for Demography and Global Human Capital, which depict global population peaking in 2070 in the medium scenario and in 2045 in the “rapid development” scenario, in which urbanization and educational gains in developing countries drive even quicker fertility declines.
As the spread between these projections indicates, long-run population forecasting is quite the uncertain endeavor. “The future of world population growth will largely be decided in Africa,” the creators of the Wittgenstein forecasts write in a recent European Union report, “with the future education of women as a main determinant of fertility playing a key role.”
Still, let’s assume that their lowest population projection is correct, and global population will peak in 2045. That’s a quarter-century from now, and population wouldn’t return to current levels until the 2090s, more than enough time for us to drive hundreds of thousands of plant and animal species extinct and perhaps boost global average temperatures enough to bring polar-ice-cap-melting chaos.
The “rapid development” scenario behind that population forecast also requires that poorer countries develop more rapidly, which in the past has meant rising per-person environmental stress. If India’s population were to stop growing tomorrow but its per-capita carbon emissions kept rising to current U.S. levels (a nearly 10-fold increase), that would lead to a 59 percent rise in global carbon emissions, all else being equal. If U.S. per capita emissions were to fall just to German levels, meanwhile, that would cut global emissions by 7 percent.
Population isn’t the only important variable here. Malthus and Ehrlich focused on it to the exclusion of all else and were blindsided by technological innovation and economic progress. Now it looks as if it will take technological innovation, political innovation, and maybe a different way of thinking about economic progress to keep the human-imposed stresses on the earth’s environment from becoming unbearable.
The possibility that our numbers could stop growing within a few decades admittedly does add a certain light-at-the-end-of-the-tunnel aspect to the difficult project of reducing the environmental damage we cause. That light could turn out to be the oncoming train of accelerating population decline. Once set in motion, downward trends in fertility rates have proved awfully hard to reverse. But after two-plus centuries of worrying about the opposite, can we maybe wait a few years before freaking out about that?