THE POPULATION EXPLOSION
The cost of energy limited the growth of technology until fossil fuels came into use, a little less than three hundred years ago. Fossil fuels contain so much energy that they provide a remarkable return on investment even when used inefficiently. When coal is burned to drive dynamos, for example, only 35% of its energy ultimately becomes electricity (Ross & Steinmeyer, 1990, p. 89). Nevertheless, an amount of electricity equal to the energy used by a person who works all day, burning up 1,000 calories worth of food, can be bought for less than ten cents (Loftness, 1984, p. 2). 3
The abundant, cheap energy provided by fossil fuels has made it possible for humans to exploit a staggering variety of resources, effectively expanding their resource base. In particular, the development of mechanized agriculture has allowed relatively few farmers to work vast tracts of land, producing an abundance of food and making possible a wild growth of population.
All species expand as much as resources allow and predators, parasites, and physical conditions permit. When a species is introduced into a new habitat with abundant resources that accumulated before its arrival, the population expands rapidly until all the resources are used up. In wine making, for example, a population of yeast cells in freshly-pressed grape juice grows exponentially until nutrients are exhausted-or waste products become toxic (Figure 1).
Figure 1. Growth of yeast in a 10% sugar solution (After Dieter, 1962:45). The fall of the curve is slowed by cytolysis, which recycles nutrients from dead cells.
An example featuring mammals is provided by the reindeer of St. Matthew Island, in the Bering Sea (Klein, 1968). This island had a mat of lichens more than four inches deep, but no reindeer until 1944, when a herd of 29 was introduced. By 1957 the population had increased to 1,350; and by 1963 it was 6,000. But the lichens were gone, and the next winter the herd died off. Come spring, only 41 females and one apparently dysfunctional male were left alive (Figure 2). 4
Figure 2. Growth of reindeer herd introduced to St. Matthew Island, Alaska (After Klein, 1968:352).
The use of extrasomatic energy, and especially energy from fossil fuels, has made it possible for humans to exploit a wealth of resources that accumulated before they evolved. This has resulted in population growth typical of introduced species (Figure 3).
Figure 3. Growth of worldwide human population (Adapted from Corson, 1990:25).
Around 8,000 BC, world population was something like five million. By the time of Christ, it was 200 to 300 million. By 1650, it was 500 million, and by 1800 it was one billion. The population of the world reached two billion by 1930. By the beginning of the '60s it was three billion; in 1975 it was four billion; and after only eleven more years it was five billion (McEvedy & Jones, 1978; Ehrlich & Ehrlich, 1990, pp. 52-55). This cannot go on forever; collapse is inevitable. The only question is when.