At some point in the early years of the 21st century, there will be a clash of two giant forces: overpopulation and oil depletion. That much has been known for a long time. It is also well known that population must eventually decline in order to match the decline in oil production. A further problem, however, is that it will be impossible to get those two giant forces into equilibrium in any gentle fashion, because of a matter that is rarely considered: that in every year that has gone by — and every year that will arrive — the population of the earth is automatically adjusted so that it is almost exactly equal to its carrying capacity. We are always barely surviving. Population growth is soaring, whereas oil production is plunging. If, at the start of any year, the world’s population is greater than its carrying capacity, only simple arithmetic is needed to see that the difference between the two numbers means that mortality will be above the normal by the end of that year. In fact, over the course of the 21st century there will be about 4 billion deaths (probably about 3.6, to be more precise) above normal.
Let us refer to those 4 billion above-normal deaths as "famine deaths," for lack of a better term, since "peak oil" in terms of daily life is really "peak food." There will, of course, also be famines for other reasons. It is also true that warfare and plague will take their toll to a large extent before famine claims those same humans as its victims. The increase in the world’s population has been rather simple: from about 1.6 billion in 1900 to about 6.1 billion in 2000 <9>. A quick glance at a chart of world population growth shows a line that runs almost horizontally for thousands of years, and then makes an almost vertical ascent as it approaches the year 2000. As Gordon and Suzuki said in 1990, "more people have been added to the Earth during the past 40 or 50 years than have been added since the dawn of man" <8>. That is not just an amusing curiosity. It is a shocking fact that should have awakened humanity to the realization that something is dreadfully wrong.
Mankind is always prey to its own "exuberance," to use William R. Catton’s term <3>. That has certainly been true of population growth. "Do you have any children?" or, "How many children do you have?" is a form of greeting or civility almost equivalent to "How do you do?" or, "Nice to meet you." But that vertical ascent of world population growth has always been hazardous. The destruction of the environment reaches back into the invisible past, and the ruination of land, sea, and sky has been well described if not well heeded. But what is not so frequently noted is that with every increase in human numbers we are only barely able to keep up with the demand: providing all those people with food, water, and living space has not been easy. We are, in other words, pushing ourselves to the limits of Earth’s carrying capacity. The same has been true for most of human history.
Even that is an understatement. In the late 20th century we actually went beyond the carrying capacity. No matter how much environmental degradation we created, there was always the sense that we could somehow get by. But in the late 20th century we stopped getting by. It is important to differentiate between production in an "absolute" sense and production "per person." Although oil production, in "absolute" numbers, kept climbing — only to decline around 2000 or 2010 — what was ignored was that although that "absolute"production was climbing, the production "per person" was not. In the year 1990 there were 4.5 barrels of oil per person per year. By the year 2000 there were only about 4.3. The same sort of problem was occurring with world grain supplies: although government sources cheerfully tell us that grain production in absolute terms is still increasing every year, what they are not telling us is that because of overpopulation the amount of grain per person is actually declining <5>. There is more grain, but there are more mouths to feed. The same problem of resources "per person" can be seen in the world’s fish catches. We are no longer getting by. We have been scraping the edges of the earth’s carrying capacity, and we are now entering a dangerous era.
EDIT
http://www.countercurrents.org/goodchild291007.htm