by Alan Weisman
In 1950, two-thirds of humans still lived rurally. Today, more than half live in cities. Urban dwellers, needing fewer farm hands, tend to have fewer children. In fact, humanity’s doubling rate has finally slowed. But slowing doesn’t mean not growing. To say that urbanization has solved overpopulation overlooks the fact that, in much of the world, the barn door was closed only after the horses had already bolted.
Even if today’s breeding generation is having fewer children per family, because their grandparents and parents had so many, every four-and-a-half days there are a million more people on the planet. Even to a schoolchild, that does not sound very sustainable.
There are now nearly five hundred cities with a million or more people. Twenty-seven cities have more than 10 million, and twelve of those have more than 20 million. (Greater Tokyo, the biggest urban area, has 35 million.) By the middle of this century, at our present decelerating pace, we’ll still add nearly half again as many people as we already have, increasing to between 9 and 10 billion,1 maybe more, all eliminating wastes and emitting carbon dioxide, all requiring food, fuel, living space, multiple services—and for those who’ve recently moved to town from the hinterlands, considerably more electricity to charge their mobile phones and plug in their inevitable TVs.
All that CO2 adds up, and keeps adding: A 2008 study by Oregon State University scientists Paul Murtaugh and Michael Schlax estimated that, predicting eventual emissions by a mother’s descendants, under current conditions in the United States, “each child adds about 9441 metric tons of carbon dioxide to the carbon legacy of an average female, which is 5.7 times her lifetime emissions.” It doesn’t take the math skills of a physicist to calculate that something is askew when five-hundred-year floods or storms start hitting twice or more in the same decade. In recent years, on every inhabited continent and archipelago, students have watched their schools drown.
As we struggle already with sustaining 7 billion, awakening to surprises like dust storms from China big enough to span oceans, or the forests of western North America, Siberia, and Australia exploding in flames, the prospect of 10+ billion not only defies our imagination, but like subprime lending, it might also defy reality. In the entire history of biology, every species that outgrows its resource base suffers a population crash—a crash sometimes fatal to the entire species. The issue may be not just whether we need to stop growing, but whether, for our own survival, we must humanely bring our numbers down from where they are now to a figure we can, literally, all live with.
Whether we accept it or not, this will likely be the century that determines what the optimal human population is for our planet. It will come about in one of two ways:
Either we decide to manage our own numbers, to avoid a collision of every line on civilization’s graph—or nature will do it for us, in the form of famines, thirst, climate chaos, crashing ecosystems, opportunistic disease, and wars over dwindling resources that finally cut us down to size. Managing population, as China has attempted, conjures frightening images of coercive governments invading our bedrooms and even our nurseries. Yet a surprising assortment of cultures have found nonintrusive ways to encourage people that smaller families might be in their own self-interest, as well as their society’s.
And the best interest of their planet?
“The idea that growing human numbers will destroy the planet is nonsense. But over-consumption will,” read a 2010 Prospect Magazine article titled “The Overpopulation Myth.” Many would agree: Reduce the amount of stuff in our lives, and shrink our footprint so that we’re not stomping the hell out of everything else. And learn to share: If we equitably distributed all the food we grow, there’d be plenty for everybody.
These are worthy goals. But the notion that everybody’s consumptive urge could be stifled anytime soon is probably wishful hoping. If saving the planet depends on changing acquisitive human nature—meaning, among other things, bucking the vast budgets of commercial advertising—the Earth will likely be thoroughly sacked long before that’s ever accomplished.
As for equal distribution of food: Does that mean among all living species, or just our own? Ever since God informed Noah that in order to start the human race anew, he had to save not just his family but all the animals, it should be understood that we can’t have a world without them. But with food production for humans currently occupying some 40 percent of the Earth’s nonfrozen terrestrial surface, plus all our roads, cities, and towns, we’ve claimed nearly half the planet for just one species—us. How are all the others going to make a living?
If everyone were vegetarian, herbivores argue, we’d only need a quarter of that land, since all the rest presently goes either to grazing livestock or to growing feed for them. (And producing a kilogram of beef emits as much carbon dioxide as an average car driving 160 miles, and uses ten times the water as a kilo of wheat.) All very true—but again, not so easy, as it’s also true that world meat demand is still rising, not falling. Most people, when they finally can afford it, tend to crave it. Healthier or not, vegans may not prevail anytime soon.
Since population is mainly growing in the poorest countries, and since poor women have the babies, to expect the weakest to rescue the world from the damage the most powerful have done to it seems grossly unjust. “Blaming environmental degradation on overpopulation lets the real culprits off the hook,” reads “10 Reasons to Rethink ‘Overpopulation,’ ” a 2006 issues paper on PopDev, a website run by Hampshire College’s Population and Development Program director and women’s health activist Betsy Hartmann. “In terms of resource consumption alone,” it continues, “the richest fifth of the world’s people consume 66 times as much as the poorest fifth. The U.S. is the largest emitter of greenhouse gases responsible for global warming—and the least willing to do anything about it.”
Except for China’s carbon emissions having now surpassed the USA’s, and the odds favoring the wealthy now being even more lopsided, these arguments are still persuasive. However, fair or not, in today’s global ecosystem everyone’s presence matters. Our numbers have reached a point where we’ve essentially redefined the concept of original sin. From the instant we’re born, even the humblest among us compounds the world’s mounting problems by needing food, firewood, and a roof, for starters. Literally and figuratively, we’re all exhaling CO2 and pushing other species over the edge. And not only is the United States an egregious polluter, it’s also still growing, faster than any other developed nation. Any discussion of population reduction that doesn’t include the USA would be pointless, let alone racist.
Then, there’s the rosy opinion that necessity has always given birth to invention when we need it, and that our creative knack for technology will surely solve the future—Israel’s technological optimism. “We learn how to dig deeper, pump faster. And we invent new sources of energy,” wrote University of Maryland economist Julian Simon in his 1996 book, The Ultimate Resource 2. The ultimate resource he referred to was human ingenuity, and he advocated population growth, so we’d have more of it.
Yet technological leaps have yet to solve anything without causing other unforeseen problems. Plus, as the hydrogen community knows, they’re hard problems. That includes the other form of hydrogen-based energy, cold fusion—basically, a controlled H-bomb—whose projected arrival seems perpetually forty years away. So far, our best alternative energy sources are solar and wind. Although there are multiple ways to apply them far more widely than we do, we’ve barely begun, and the world’s biggest business, intent on squeezing the last drop of petroleum out of the Earth’s crust, isn’t helping matters much. Even if we vastly improved our energy efficiency, to ramp solar and wind up to meet the demands of all our transport and industries, and of our Chinas and Indias, would be far beyond their capacity to deliver at this point.
And even if we somehow conjured up a truly limitless, emissions-free energy source, it wouldn’t cure traffic, or sprawl, or noise pollution. Inevitably, it would only stimulate hunger for more r
esources. However, the one technology that in fact could make a dent in our collective impact is one we already have: the one that lets us curb the number of consumers.
Family planning—a less onerous term for birth control—can’t solve everything: we still should try to convert everyone possible, especially the coming generation, from energy-addicted carnivores into sharing, environmentally astute, low-carbon sustainers. It’s also not without its perils: like anything else humans do, it can be, and has been, misused for evil, such as eugenics. And if population reduction implies a shrinking economy, we’re already plenty scared of that one. Yet when numbers come down, as Japan, whose aging population is already on the verge of shrinking, is discovering, there may be new opportunities for prosperity that we missed in the mad rush to grow and grow more, until we smash into reality.
Among them is the chance to equalize things far better than we have. So let’s define optimum population as the number of humans who can enjoy a standard of living that the majority of us would find acceptable. A standard of living, say, roughly equivalent to a European level, pre-euro-crisis2 : far less energy-intensive than the United States or China, far more hospitable than much of Africa or Southeast Asia, and with the highest possible percentage of educated, enabled women—which may be the most effective contraceptive of all.
So how many is that? And how do we get there?
Since it took nearly two hundred thousand years since Homo sapiens first appeared for our population to reach 1 billion, around 1815, and now we suddenly have seven times that many—how the hell did that happen? How did we get here?
CHAPTER 3
Body Counts and the Paradox of Food
i. Bodies
Genetic evidence suggests that at some point between fifty thousand to one hundred thousand years ago, our Homo sapiens ancestors possibly numbered as few as ten thousand. Then they began to wander out of Africa, following the species corridor north through present-day Israel and Palestine and branching into Europe, Asia, and beyond. Discovering more sustenance as they spread, they began to increase, but almost imperceptibly. As the Worldwatch Institute’s Robert Engelman notes in his book More, had they multiplied at modern growth rates (currently 1.1 percent annually worldwide, which means doubling every sixty-three years), within a few millennia, not just Earth but the entire solar system couldn’t have contained us.
The simple reason population remained low until recent human history was that people died about as fast as people were born. For tens of thousands of years, most of them likely didn’t see their first birthday. Birth rates might be high, but so were infant mortality rates. A woman would give birth to seven, and two might live.
Two people, one man and one woman who produce two children, essentially replace themselves.1 Any more than two, population grows. The fact that population grew so slowly until about two centuries ago means that the average number of children who lasted long enough to have children themselves was barely more than two. For every family with more than two who survived to adulthood, others had only one or none who made it—at any number below two, population contracts.
Occasionally, it contracted dramatically, such as during the Black Plague, which killed off an estimated one-fourth of humanity in the mid-fourteenth century. But even without unusual epidemics, the general pall of death that hung over every family didn’t began to dissolve until 1796. That year, British surgeon Edward Jenner discovered a vaccine for smallpox, a disease that used to knock back our numbers each year by the millions. Jenner’s cure was also the first vaccine for anything. It inspired nineteenth-century French chemist Louis Pasteur to develop others, against rabies and anthrax. Pasteur made two other key contributions to human survival. One was the familiar process our dairies still use. Pasteurization extended the shelf life of milk, which improved nutrition and reduced infections from pathogens such as salmonella and those causing scarlet fever, diphtheria, and tuberculosis.
Pasteur was also instrumental in convincing humanity that disease did not occur through some mysterious spontaneous generation, but was spread by germs. In the nineteenth century, hand soap became common for the first time, both in homes and in hospitals. Before, patients died as often from infections picked up from a surgeon’s unsterilized hands and scalpel as from the ailment he was trying to fix. One of the first uses of surgical disinfectant was in a maternity ward in Vienna, where doctors washing their hands in a chlorine solution lowered both infant and maternal mortality by a factor of ten—an innovation with a direct impact on the number of living humans.
In the twentieth century, medical advances kept coming, each saving—and extending—more human lives. After Cuban microbiologist Carlos Finlay pinpointed the carrier of the yellow fever virus, American doctors William Gorgas and Walter Reed implemented the world’s first massive mosquito control program, without which the Panama Canal would never have been completed. More vaccines for diphtheria, tetanus, and finally polio, and the crucial invention of antibiotics, all lowered mortality and increased longevity—which meant that more total people, young and old, were alive. In 1800, average life expectancy at birth for most humans was forty years. Today, in much of the world, it’s nearly double.
More people not dying early and living longer: Who could object to that? “The humane goals of lowering the death rate are very important to me,” admits Albert Bartlett cheerfully, “if it’s my death they’re lowering.”
No disagreement from anyone over forty, who might well not be alive without these medical victories. Probably nobody else will protest, either. So any discussion of an optimum population for the human race must assume optimal health care. The idea of lowering medical standards to limit our numbers is no more acceptable than thinning ourselves by selective culling.
That doesn’t dismiss, however, an ethical argument raised by the implications of further medical advances. If any of the current greatest challenges—say, finding cures for malaria or HIV—were successfully met, it would spur a significant uptick in humanity’s census. Malaria alone kills a child every thirty seconds. If children stop dying from it, they’ll survive to reproduce more children who also won’t die of malaria. As it would be unconscionable to oppose malaria eradication just to keep human numbers in check, the question becomes whether funders of malaria and HIV research have a moral obligation to also fund family planning—lest our numerical impact threaten the very ecological underpinnings of human life.
Thus far, there’s no vaccine against extinction.
ii. Brave New Cornucopia
The other reason that humanity ballooned so suddenly in the last century was an unprecedented increase of the food supply. To be able to nourish everyone on Earth sounds like another moral no-brainer. Yet this one’s a little trickier. It raises a paradox that, at first, seems as counterintuitive as the unexpected results of exponential doubling.
The growing number of people was crucial to the success of the labor-intensive European Industrial Revolution. But it also meant that Europe had to produce more food than ever before to feed them. A German chemist, Justus von Liebig, is credited with two contributions to that cause—one huge, the other monumental. The huge one was developing the world’s first infant formula. Whether his creation was, as he claimed, nutritionally equivalent to mother’s milk is still hotly contested. Nevertheless, it freed many mothers from the exhausting business of breast-feeding indefinitely, and it allowed their babies to survive early weaning. And since lactation releases hormones that tend to suppress ovulation, less breast-feeding resulted in even more pregnancies.
Justus von Liebig’s second, monumental discovery was that nitrogen, along with phosphorus and potassium, is one of the essential nutrients for plants. Although he is considered the inventor of fertilizer, he was not responsible for the artificial nitrogen fertilizer used today, an innovation that probably changed the course of human events more than any other in modern history, cars and computers included. That would come later. In von Liebig’s day, commercial nitr
ogen fertilizers came chiefly from the excrement of seabirds and bats. Particularly prized was guano from islands off the coast of Peru, where cormorants, pelicans, and gannets that fed on enormous schools of nutrient-rich anchovetas had deposited layers of white poop 150 feet thick. In the nineteenth century, galleons and steamships carried more than 20 million tons of it around Cape Horn to Europe.
Having neglected to patent his discoveries, von Liebig profited little from them. Later, chagrined at the riches accrued by Nestlé and other competitors, he did secure the rights to one last invention that arguably contributed to human nutrition: the beef bouillon cube.
The essential nutrient nitrogen is a gas so relatively inert that, unlike hydrogen, there’s plenty of it floating around in its free state. In fact, over three-fourths of the air we breathe is pure nitrogen. Nothing in our lungs chemically combines with it, so we harmlessly exhale it away. In all nature, only one family of enzymes can fix airborne nitrogen—that is, absorb and chemically convert it into a nongaseous form, such as the plant food ammonium. And just a few plants host bacteria bearing these enzymes, which, in return, get fed by nodules on their roots.
They are mainly legumes, such as lentils, beans, clover, soy, peas, alfalfa, gum acacia, and peanuts. Until synthetic fertilizer, such symbiotic plant-bacteria pairs were the main source of nitrogen in soil, limiting the amount of plant life the planet could produce. Virtually anything green that grew was benefiting from nitrogen that leguminous plants had fixed. For that reason, farmers traditionally would rotate legumes with grains, or grow them together (such as corn and beans in Latin America), or plow cover crops like nitrogen-rich clover into their fields to replenish them.
