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The real question is, how many people can the planet sustain? As Cohen notes in his book How Many People Can the Earth Support?, microbiologist Anton van Leeuwenhoek calculated a carrying capacity of roughly 13.4 billion people back in 1679, based on the population density of his native Holland and its size relative to the rest of the globe. Modern guesses are hardly more scientific, ranging from as few as 1 billion (recently proposed by James Lovelock as our likely number by 2100 thanks to catastrophic climate change) to as many as 1 trillion.
“These estimates are political numbers, intended to persuade people, one way or another: either that too many humans are already on Earth or that there is no problem with continuing rapid population growth,” Cohen writes.
As early as 1948, scientists began to link explosive modern population growth and catastrophe. Ornithologist William Vogt’s Road to Survival warned of impending demographic doom—as have numerous conservationists and environmentalists in the subsequent decades, perhaps most famously biologist Paul Ehrlich (The Population Bomb) or Donella and Dennis Meadows (The Limits to Growth). In Ehrlich’s case, observations of butterflies breeding so fast as to consume all available food—and then dwindling away—inspired him to predict the same fate for humans.
This is not a new idea, mind you. As early as 1600 B.C., when total population was less than 50 million, Babylonians worried that the world was too full of people, according to Cohen. The predicted human population of 2050—9 billion people—would have been inconceivable at that time.
That’s because human ingenuity—whether through the waterworks of ancient Babylon or the more modern breeding of staple crops such as wheat for higher yields, known as the “Green Revolution”— has outpaced, so far, the pessimism of apocalyptic environmentalists.
Agronomist Norman Borlaug and colleagues created a strain of dwarf wheat that staved off famine for hundreds of millions in the 1960s and 1970s—increasing India’s harvest alone by nearly 170 percent in less than a decade. Yet “there can be no permanent progress in the battle against hunger until the agencies that fight for increased food production and those that fight for population control unite in a common effort,” Borlaug said in his acceptance speech for the Nobel Peace Prize in 1970. “[Man] is using his powers for increasing the rate and amount of food production. But he is not yet using adequately his potential for decreasing the rate of human reproduction. The result is that the rate of population increase exceeds the rate of increase in food production in some areas.”
That demographic contradiction is nowhere more true than in many countries of sub-Saharan Africa, where a population of 800 million must subsist on local yields of 1 metric ton per hectare—one-third of yields in the rest of the developing world and one-ninth those of the U.S., Europe, Australia and other parts of the developed world.
Genetic modification might boost yields. Such technology is “critical for achieving the ecological intensification required to meet human food demand on a global scale,” says agronomist Kenneth Cassman of the University of Nebraska–Lincoln. And genetic modification may prove critical to meet the challenge of crop stress due to climate change, dwindling topsoil and billions more mouths to feed. But it is currently illegal in most of Africa, according to political scientist Robert Paarlberg of Wellesley College, and faces serious public concern and regulatory challenges in the U.S., Europe and other parts of the world.
Still, there is still plenty of room for improvement by more conventional means: the targeted application of fertilizer and the like. The Earth Institute’s Millennium Village of Sauri in Kenya has tripled yields even in the face of a crippling drought gripping the region, and Malawi doubled yields through fertilizer subsidies in just four years.
Nor is the growth of human population an unmitigated ill. After all, more people means more minds and hands devoted to solving the pressing problems of increasing yields, biodiversity loss and economic sustainability—as can be seen in many portions of Africa today. As economist Ester Boserup argued in the 1960s: Population growth may drive agricultural innovation, from the plow to Borlaug’s dwarf wheat, rather than the other way around.
Ten Thousand Ton Child
Yet apocalyptic biologists have a strong case as well. Fifty percent of all temperate grasslands and forests have disappeared, largely under the plow. More than 16,000 known species face extinction (785 have already been lost) and as many as 12,000 species unknown to science disappear each year, according to biologist E.O. Wilson of Harvard University. More than 90 percent of some commercial fish species, such as cod, pollock and haddock, are gone. Water tables around the globe plummet precipitously, thanks to human withdrawals for agriculture. And population growth to 9 billion people alone will add as much as 2 billion metric tons more of carbon dioxide to the greenhouse gas blanket smothering Earth.
“The inexorable increase in human numbers is exhausting conventional energy supplies, accelerating environmental pollution and global warming, and providing an increasing number of failed states where civil unrest prevails,” writes reproductive biologist Roger Short of the University of Melbourne in the introduction to a special issue of Philosophical Transactions of the Royal Society B—a journal from the U.K.’s Royal Society whose motto is “Take nobody’s word for it.”
Short goes so far as to call for a halt to future population growth. After all, the most profound way a U.S. citizen can impact climate change is to have fewer children, since every American child born today will add almost 10,000 metric tons of CO2 to the atmosphere under current conditions—five times more than a Chinese child and 160 times more than a baby from Bangladesh. Having one fewer child would reduce a family’s greenhouse gas impact 20 times more than driving a Toyota Prius, using Energy Star appliances and other environmentally friendly lifestyle choices combined, according to researchers at Oregon State University.
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