Human Population Reaches 7 Billion—How Did This Happen and Can It Go On?

Features | Energy & Sustainability

A mere 12 years after surmounting six billion, the world's population will reach seven billion, according to the U.N. But that rate seems to be slowing

By David Biello ?| October 28, 2011?|

SEVEN BILLION: There are now seven billion people on the planet--and growing. Image: ? iStockphoto.com / selimaksan

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• MP3 file Audio How Many People Can Earth Hold? Well...

On October 31, 2011, a particularly special person will be born?the seven billionth human alive, according to United Nations demographers. He or she could be delivered by a starving mother in the growing wastelands of Somalia, a failed-state gripped by famine and war. The best odds are that the child will be born in India, which has the highest rate of births per minute in the world. She may even be an American girl, heiress to a complex legacy that is in no small part responsible for the fact that, for better or worse, people are shaping the destiny of the planet that engendered humanity.

Regardless, the seven billionth person raises the question: How much is too much? "Can Earth support seven billion or nine billion or 10 billion people in a good life for a long time?" asked demographer Joel Cohen of Columbia University's Earth Institute at its human population event on October 17. "The addition of four billion people in five decades has no precedent. That is an exceptional event and will probably never be repeated within human history."

There were only one billion people on the planet as recently as the turn of the 19th century and only a few hundred thousand just 10,000 years ago. In fact, there may have been as few as 15,000 of us, roughly 70,000 years ago.

With both more people and longer lifetimes, humanity's absolute numbers continue to rise, even though the number of children per women has halved since 1950. In fact, the absolute growth rate in human population peaked at 2.1 percent between 1965 and 1970, according to Cohen. "We're now down to 1.1 percent per year," he said, although that still means roughly 150 babies born every minute.

Consumers
The world's richest 500 million people produce half the world's carbon dioxide emissions?the primary greenhouse gas responsible for climate change?whereas the poorest three billion emit just seven percent. The average American?one of 312.5 million?uses up some 88 kilograms of stuff daily: food, water, plastics, metals and other material goods. Americans consume a full 25 percent of the world's energy despite representing just 5 percent of global population, and the band of industrialized nations combine to waste 222 million metric tons of food per year, according to the U.N. Food and Agriculture Organization.

"Population doubled while the economy grew by 15 times, cars by 16 times and fertilizer-use by sixfold," said geographer Ruth DeFries of Columbia at the same event. "There is no end in sight for that increase in consumption," particularly as it is emulated by people around the globe.

All this consumption requires a host of natural resources, from vast copper mines scarring the landscape to ever more land for food. More acreage was converted to growing crops between 1950 and 1980, than from 1700 to 1850, and arable land is one of nine "planetary boundaries" that scientists have identified?limits past which humanity should fear to tread. The others include: climate change, biodiversity loss, nutrient cycles, ocean acidification and freshwater use, among others. "Slowing population growth does not solve all the problems but it makes it easier by slowing demands," Cohen said.

Source: http://rss.sciam.com/click.phdo?i=e8617776289b20bdbf848073ab84e19c

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