Causes of Population Growth

While reading 'The End of Poverty' by Jeffrey Sachs some time ago, a world population chart that he presented got me to thinking. The chart shows a nearly stable world population from 1 CE to around 1000 CE, a slight increase in growth until 1500 CE, accelerated growth from 1500 to 1700 CE, and then the 'hockey stick' of growth: 900 million people in 1700 to 6.5 billion people today - a scant 300 years later.

In other reading, two significant events occurred that appear to coincide with the increases in growth rate: After 1500 the exploitation of coal as an energy source, and after 1700, the exploitation of oil. It seems a perfectly causal event: More exploited energy leads to more food production which leads in turn to more population. We did see the mechanization of farming, especially after 1800 in the US, which allowed 1 farmer to produce food to feed much more than just his family.

However, something about this explanation doesn't appear to fit the facts: As far as I am aware, the exploitation of coal and oil did not occur at the same rate in China and India, the two world population leaders. According to statistics, China's population rose from around 100 million people in 1735 to 300 million by 1785, rose to 400 million by the middle of the 19th century, and stands above 1 billion people today.

Rose George, in her book 'The Big Necessity', offers a clue. She writes that the Chinese have a 4000 year history of spreading their excrement on their fields as fertilizer, and, despite its offensive odor, it is very, very good at renewing the productivity of the farm. As the value of 'night soil' rose, so did the efficiency with which it was collected and distributed (until very recently the majority of Chinese used buckets to collect their waste, which was set out in the morning for collection, rather than dumped in the street like Europe). She continues: "In the vicious circle of night-soil fertilizer production, more people were produced and more people produced more night soil, which produced more crops, which fed more people. (p118)"

As their population has outstripped this method of fertilization, China has moved to rely on petroleum based fertilizers, further increasing food production and population. But it does provide another piece of the puzzle related to our massive population expansion worldwide.