Demographic Significance of the 40 Factor

Human survival depends on there being enough food and drink to support life. Fresh water is easily obtained in many parts of the world. Food, on the other hand, has to be grown, raised or hunted. Producing enough of it, by agriculture, is serious work. Before about 1750, when the Industrial Revolution began, farmers depended on human and animal muscle. Now, in all but backward societies, diesel-powered tractors and mains electricity have taken over. The increase in efficiency is colossal.

Over the hedge from my garden is a hay meadow 7 acres (2.8 hectares) in area. Mowing it by tractor takes about 1.5 hours. This compares to the full day, including breaks for food and cider, that a man with a scythe traditionally took to cut one acre. The tractor is roughly 40 times more efficient in terms of man-hours.

The next two procedures in modern haymaking, tedding the cut grass to dry it, and then baling it, each take the tractor about 1.5 hours. Before 1750 the farm workers, men and women, used rakes to aerate and dry the hay, then loaded it into carts with pitchforks. Again the efficiency ratio is something like 40:1.

A giant combine harvester with its satellite tractors and trailers may be 100 times as effective as the peasants with their sickles and threshing floors in recovering the grain from large acreages of cereals.

Medieval woodcutters harvested energy with sharp axes. Several of them would have taken a day to load their cart with logs and haul it from the forest to the village. Thanks to my chain saw I can fill my car with logs cut to size and bring them home, a mile from the wood, in two hours.

Only 60 years ago, before piped water reached the streamless limestone plateau of the Mendip Hills, my neighbour’s cattle were supplied in summer by a horse and cart that carried a few large churns of water up the hill from the farm to a tank on the plateau 150 metres higher. The horse managed 2 journeys a day to water the little herd of about 10 animals. Now there is no limit to the number of cattle that can be watered.

Picture the dairymaid on her three-legged stool, milking about 5 cows every hour by hand a century ago. Now, only the capacity of the milking parlour limits the size of the herd, sometimes as many as 400, that can be processed in two or three hours.

Whether it be ploughing the fields, hedging and ditching, clearing out ponds, or raising livestock, few modern agricultural procedures are less than 40 times as efficient, in terms of food produced, as they were when the work was done by humans, with or without farm animals.

The significance of this “40 Factor” cannot be exaggerated. How long do we have before fossil fuels are so scarce that global food production begins its shrinkage to about one fortieth of present capacity?

According to the prestigious Association for the Study of Peak Oil and Gas (ASPO), annual production of conventional oil peaked in 2005 at 24 Gb (billion barrels) and total oils (including heavy oil, tar sands, oil shales, deepwater, polar and gas condensates) are expected to peak in 2011 at 33 Gb. All hydrocarbons including gas will peak about 2012. The world’s large coal reserves are fairly irrelevant because they are slow and expensive to mine and process into liquid fuels.

So the downhill slide in fossil fuel production, food availability and world population may well begin around 2012, or sooner if war breaks out in the Middle East or other oil-rich region. Depending on a host of variables it could end around 2150. The journey will be eventful, to say the least, and we must hope that our descendants will have learned from it as they try to survive in the hard world of non-fossil energy.

Dr William Stanton