A Story by Randy Olson

7 Billion Humans | National Geographic Magazine

By the United Nations estimates, the world’s population is now over seven billion. The first billion people accumulated over our entire history until the early 1800s. The second took an additional 120 years. In the last 50 years, we have doubled, going from three billion in 1959 to four billion in 1974, five billion in 1987 and six billion in 1998. This is no historical precedent for this population increase.

7 Billion Humans | National Geographic Magazine

By Randy Olson

By the United Nations estimates, the world’s population is now over seven billion. The first billion people accumulated over our entire history until the early 1800s. The second took an additional 120 years. In the last 50 years, we have doubled, going from three billion in 1959 to four billion in 1974, five billion in 1987 and six billion in 1998. This is no historical precedent for this population increase.

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Crowds Flock to Kuchuru Town Riverbank at the Sound of a Boat Motor, Lower Omo River Valley, Ethiopia Some 850 million to 925 million people experience food insecurity or chronic undernourishment. In much of Africa and South Asia, more than half the children are stunted (of low height for their age) as a result of chronic hunger. While the world produced 2.3 billion metric tons of cereal grains in 2009-10 — enough calories to sustain 9 to 11 billion people — only 46 percent of the grain went into human mouths. Domestic animals got 34 percent of the crop, and 19 percent went to industrial uses like biofuels, starches and plastics. —Joel E. Cohen, author of “How Many People Can the Earth Support?”
The Future of Shanghai, China is Laid Out at the City Planning Museum  …each American child generates seven times as much carbon dioxide over time as one child in China, and 169 times as much as one in Bangladesh. Reducing car travel, recycling and making homes more energy efficient would have a fraction of the impact on emissions that reducing the birth rate would, it found. —Mireya Navarro, New York Times, October 31, 2011
Huge Crowds at Water Fight at China Folk Culture Villages | Shenzhen, China But there is plenty of bad news, too. Nearly half the world lives on $2 a day, or less. In China, the figure is 36 percent; in India, 76 percent. More than 800 million people live in slums. A similar number, mostly women, are illiterate. —Joel E. Cohen, author of “How Many People Can the Earth Support?”  
Untouchables Bathing in Former British Horse Watering Trough in Mumbai, India At the birth of Jesus, the global population was an estimated 200 million. (It was probably easier then than now for the meek to inherit the Earth.) It took until the early 1800s to reach one billion. We went from six billion to seven in a veritable blink of the eye: 12 years. In 1950, for each person 65 and older, there were more than six children under 15. By 2070, elderly people will outnumber children under 15. —Joel E. Cohen, author of “How Many People Can the Earth Support?”
Crowds at Pilgrimage City | Varanasi, India Water shortages are projected to be significant in northern Africa, India, China, parts of Europe, eastern Australia, the western United States and elsewhere. Climate changes will increase the water available for agriculture in North America and Asia but decrease it in Africa, Latin America and the Caribbean. Similar stories could be told about land, overfishing and carbon and nitrogen emissions to the atmosphere. Where is this taking us? The coming half century will see huge shifts in the geopolitical balance of numbers, further declines in the number of children per woman, smaller but more numerous households, an increasingly elderly population, and growing and more numerous cities. —Joel E. Cohen, New York Times, October 23, 2011
Sea of Humans | Ratha Yatra Religious | Puri, India But there is plenty of bad news, too. Nearly half the world lives on $2 a day, or less. In China, the figure is 36 percent; in India, 76 percent. More than 800 million people live in slums. A similar number, mostly women, are illiterate… Some 850 million to 925 million people experience food insecurity or chronic undernourishment. In much of Africa and South Asia, more than half the children are stunted (of low height for their age) as a result of chronic hunger. While the world produced 2.3 billion metric tons of cereal grains in 2009-10 — enough calories to sustain 9 to 11 billion people — only 46 percent of the grain went into human mouths. Domestic animals got 34 percent of the crop, and 19 percent went to industrial uses like biofuels, starches and plastics. —Joel E. Cohen, New York Times, October 23, 2011    
Crowds at Ratha Yatra Religious Festival | Puri, India Human demands on the earth have grown enormously, though the atmosphere, the oceans and the continents are no bigger now than they were when humans evolved. Already, more than a billion people live without an adequate, renewable supply of fresh water.   —Joel E. Cohen, author of “How Many People Can the Earth Support?”
Karo Tribal Area Losing Water Supply | Labuk Village, Ethiopia A United Nations report released on Tuesday projects that world population, instead of stabilizing at above 9 billion by 2050, will keep growing and may hit 10.1 billion by 2100. The population of Africa, for instance, could more than triple, rising to 3.6 billion by century’s end. Nigeria, the continent’s most populous nation, could see its population increase from 162 million today to 730 million by 2100. Accelerating rates of growth are already evident: world population is expected to pass 7 billion in October, only a dozen years after reaching 6 billion.
Dharavi Slums | Largest Slums in the World | Mumbai, India The world’s population will hit seven billion on Oct. 31. Or maybe not until next year. Or maybe it has already happened… That lack of calendar clarity highlights how much remains unknown about the world’s population today—which makes projecting future population even tougher. Both the U.N. and the Census Bureau build their figures using a mix of national census data, population surveys in developing countries and demographic expertise… But not every nation carries out a census, and the U.N. says it hasn’t been able to use census data more recent than 2005 for countries that contain 62% of the world’s population. It has no data, census or otherwise, for 25% of the world’s people since 2005.  —Carl Bialik, The Wall Street Journal, October 22, 2011
Shibuyu | Most Crowded Intersection | Tokyo, Japan Although birthrates and death rates have both declined sharply since the 1960s… death rates have declined more rapidly than birthrates. The cumulative effect of the excess of births over deaths in recent decades has led to a successive attainment of billion-person milestones every 12 or 13 years. —Sam Roberts, New York Times, November 1, 2011
Camel Beauty Contest | Empty Quarter, Abu Dhabi For some in the West, the greatest challenge — because it is the least visible — is to shake off, at last, the view that large and growing numbers of people represent power and prosperity. This view was fostered over millenniums, by the pronatalism of … Arab thinkers like Ibn Khaldun… more workers, more consumers, more soldiers… “The number of the people makes the wealth of states,” said Frederick the Great. This view made some sense for societies subject to catastrophic mortality from famines, plagues and wars. But it has outlived its usefulness now that human consumption, and pollution, loom large across the earth. —Joel E. Cohen, New York Times, October 23, 2011
Largest Migration in Human History From Rural to China’s Cities | Huaxi Village, China According to United Nations demographers, 6,999,999,999 other Earthlings potentially felt the same way on Monday when the world’s population topped seven billion. But if you’d rather go by the United States Census Bureau’s projections, you’ve got some breathing room. The bureau estimates that even with the world’s population increasing by 215,120 a day, it won’t reach seven billion for about four months. How do the dueling demographic experts reconcile a difference, as of Monday, of 28 million, which is more than all the people in Saudi Arabia? They don’t. “No one can know the exact number of people on the globe,” Gerhard Heilig, chief of the population estimates and projections section of the United Nations Population Division, acknowledges. Even the best individual government censuses have a margin of error of at least 1 percent, he said, which would translate in the global aggregation to “a window of uncertainty of six months before or six months after Oct. 31.” An error margin of even as little as 2 percent would mean that Monday’s estimate of seven billion actually was 56 million off (which is more people than were counted in South Africa). —Sam Roberts, New York Times, Nov 1, 2011
Phoenix Naturalization Ceremony | USA While seven billion is a nice round number, knowing the identity of the lucky baby or the exact moment the threshold is crossed isn’t really any more important than pulling over to the side of the road to bask in your car’s 100,000th mile. But the building blocks for world population estimates—national demographic statistics and characteristics—are used by governments, businesses and aid groups to plan spending and spot potential trouble spots.  —Carl Bialik, The Wall Street Journal, October 22, 2011
Fertility Mendicants | Near Lahore, Pakistan With rising per capita consumption, by 2100 we’ll need to produce an amount of food that is 2.5 times what all societies have produced in the last 8,000 years. We currently use 33 percent of the Earth’s surface for food. As 25 percent isn’t usable (deserts, cities, roads) and 12 percent is set aside for national parks and the like, we continue to expand the food production frontier each year. At the current rate of habitat loss, after 40 years, we will have “eaten” nearly all the remaining natural habitat on the planet. Whatever is sustainable with 7 billion people will not be with 10 billion.  —Jason Clay, senior vice president at the World Wildlife Fund
Half of Uganda is Under the Age of 15 | War Victims and Public School Children | Lira, Uganda High fertility rates are driving rapid population growth in Africa. Globally, women are having an average of 2.5 children over the course of their childbearing years. But the average African woman is having nearly 4.5 children (and over 6 in four countries). One consequence of Africa’s high fertility is that a preponderance of its population is young. Twenty-seven percent of the world’s population is under age 15, but in Africa, the figure is 40 percent. —David E. Bloom, chairman of the department of global health and population at Harvard. 
Extreme Mustang Makeover | Fort Worth, Texas, USA The urban population of developing countries is expected to grow by a million people every five days through at least 2030, while the rural population falls. Many cities will eat into prime agricultural land unless they grow in density, not extent. And nearly half of urban population growth by 2015 will occur in cities of fewer than half a million people. —Joel E. Cohen, author of “How Many People Can the Earth Support?”
Indian Sikh festival in Ramblas Catalunya | Barcelona, Spain The first billion people accumulated over a leisurely interval, from the origins of humans hundreds of thousands of years ago to the early 1800s. Adding the second took another 120 or so years. Then, in the last 50 years, humanity more than doubled, surging from three billion in 1959 to four billion in 1974, five billion in 1987 and six billion in 1998. This rate of population increase has no historical precedent. —Joel E. Cohen,  author of “How Many People Can the Earth Support?”
Crowds on the streets of Calcutta | Bengal State, India At the birth of Jesus, the global population was an estimated 200 million. (It was probably easier then than now for the meek to inherit the Earth.) It took until the early 1800s to reach one billion. We went from six billion to seven in a veritable blink of the eye: 12 years. In 1950, for each person 65 and older, there were more than six children under 15. By 2070, elderly people will outnumber children under 15. —Joel E. Cohen,  author of “How Many People Can the Earth Support?”