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, access to contraception, downsized family expectations, and other cultural changes—take more time. And just like a bank account, when the death (spending) rate falls faster than the birth (savings) rate, the result is a rapid run-up in the sum total. Even if fertility rates later fall to match death rates—thus completing the Demographic Transition and halting further growth—a new, much larger population balance is then carried forward.
In the twentieth century, one Demographic Transition concluded and another began. In Europe and North America it took from about 1750 to 1950 to complete, making these places the fastest-growing in the world while most of Asia and Africa grew slowly. This growth then slowed or stopped as industrialized countries completed the Demographic Transition, their fertility rates falling to near or even below the death rate.
But in the developing world, a new Demographic Transition that began in the early twentieth century with the arrival of modern medicine has still not finished. Thanks to the inventions of antibiotics and vaccines, along with insecticides to control diseases like malaria, death rates have plummeted17 but fertility rates, while dropping, have fallen less quickly. In some countries they haven’t fallen at all, defying the classic Demographic Transition notion that all modernized women prefer fewer babies. Such discrepancies underline a known weakness of the Demographic Transition model: Not every culture will necessarily adopt the western ideal of a small nuclear family, even after women’s rights, health, and security conditions improve.
So somewhere around 1950, our fastest population growth rates left the OECD countries18 and went to the developing world. Because the base population levels in the latter are so much larger, the resulting surge in world population has been nothing short of phenomenal. In most developing countries the spread between fertility and death rates, while narrowing, remains substantial. This second Demographic Transition is not yet finished, and unlike before, it involves the vast majority of the human race. Until a few decades after it ends—if it ends—world population will continue to grow.
The second global force, only partly related to the first, is the growing demand that human desires place upon the natural resources, services, and gene pool of our planet.
It’s difficult to comprehend how fully dependent we are upon these things. Steel machines burn oil to grow and harvest our grains, with fertilizers made from natural gas, generating many times over what a farmer and mules could produce on the same land. From the genetic code of organisms we take the building blocks for our food, biotech, and pharmaceutical industries. We frame our buildings with timber, steel, and cement. We take water from the ground or trap it behind dams to grow alfalfa and cotton in the desert. We need trucks and diesel and giant metal-hulled ships to move ores and fish and manufactured goods from the places that have them to places that want them. The resulting trade flows have grown entire economies and glittering cities, with their music and culture and technology. Coal-fired electricity zaps through billions of miles of metal cable to power buildings, electric cars, cell phones, and the Internet. Airplanes and cars burn the sludge of long-dead things, granting us personal freedom and the chance to see the world.
It’s no secret that our twentieth-century expansions in population, modernization, trade, and technology have escalated demand for all of these. Public concern—both for the stability of raw commodity supplies and for the health of the natural world—has been high since the 1970s, especially after the OPEC oil embargo crisis of ’73-’74 and NASA’s launch of ERTS-1 (later renamed Landsat), the first civilian satellite to disseminate graphic images of clear-cuts gnawing away the vast rain forests of the Amazon basin. Today, news feeds crackle with stories about dwindling oil, fights over water, and soaring food prices. Many plants and animals are disappearing as their habitats are converted to plantations and parking lots. Still others have been harvested into oblivion. Fully
Perhaps no resource pressure has grown faster than our demand for fossil hydrocarbon fuels. This began in Europe, North America, Australia, and Japan and has now spread to China, India, and other modernizing nations. Because the United States has been (and still is) the largest consumer of these fuels, let’s illustrate the rapacity of this phenomenon as it has unfolded there.
In 1776, when the United States of America declared independence from Great Britain after a little over a year of war, most of the fledgling country’s energy came from wood and muscles. Yes, there were sawmills turning waterwheels to cut logs, and coal was used to make coke for casting iron cannons and tools, but the vast majority of America’s energy came from fuelwood, horses, mules, oxen, and human backs.
By the late 1800s, the Industrial Revolution, steam locomotive, and westward expansion had changed all that. Dirty black coal was the shining new prince—fueling factories, coke ovens, foundries, and trains all across the young nation. Coal consumption grew from 10 million short tons per year in 1850, to 330 million short tons just fifty years later.20 Little mining towns sprang up all over Appalachia, like now-defunct Ramseytown in western Pennsylvania, where my grandmother was later born. Nearby Rossiter produced my grandfather, who worked in the coal mines as a teenager.
But in the twentieth century, coal was surpassed. Oil, first drilled out of a quiet Pennsylvania farm in 1859 to make lamp kerosene, caught on slowly at first. Gasoline was originally a junk by-product that some people dumped into rivers to get rid of. But then someone thought of pouring it into a combustion engine, and gasoline became the fuel of Hercules.
Packed inside a single barrel of oil is about the same amount of energy as would be produced from eight years of day labor by an average-sized man. Seizing oil fields became a prime strategic objective in both world wars. The Baku fields of Azerbaijan were a prime reason that Hitler invaded Russia, and it was their oil supply, gushing north to the Russian army, that stopped him.
By the end of World War II, cars and trucks had outgrown the rail system, locomotives had switched to diesel, and the liquid-fuels market was really taking off. Oil consumption surpassed coal in 1951, though sales of both—along with natural gas—continued to rise strongly. In just one hundred years (1900-2000) Americans ramped up their coal consumption from about 330 million to 1.1 billion short tons per year,21,22 a 230% increase. Oil-burning grew from 39 million to 6.6
Although the U.S. population also rose quickly over this same time period (from 76 to 281 million, or +270%), oil consumption rose far faster on a per capita basis. By the beginning of the twenty-first century the average American was burning through more than twenty-four steel drums of oil every year. In 1900, had my Italian grandfather already emigrated to the United States, he would have used just twenty-two gallons, about one-half of
