This is a guest post by Dr. Gary Peters, retired geography professor and author of Population Geography.
The growth of the human population cannot continue forever—there is a limit to our numbers, even if we cannot specify what that limit might be. There is also a limit to how much oil can be extracted from our planet, even if we don’t know exactly how much oil there really is. These two variables are related because cheap oil has allowed us to support a population that is much larger than it would be otherwise. Despite more than 200,000 years of living and growing, the population of Homo sapiens never even reached one billion before the beginning of the era of fossil fuels. Today there are nearly seven billion of us and much of the era of fossil fuels is becoming visible in the rearview mirror. Demographers have suggested two demographic transition models to explain what has happened to the human population over the last two centuries. I’m suggesting that a third demographic transition model will be necessary to explain what is likely to happen in coming decades.
The first demographic transition. The original (or classical or traditional) model of demographic transition had its genesis in the work of Warren Thompson, dating back to 1929. Though improved in many ways since then, essential features of the demographic transition model remain simple and well-known, as shown in the illustration below. Economic growth drove demographic changes in ways never seen in earlier pre-industrial societies.
The basic demographic transition model is based on historical declines in mortality and fertility that occurred from the eighteenth century onward in several European populations. Though the model is not a good predictive device, the demographic transition has continued in many non-Western countries as well. It is often cited as the reason why we should not worry about future population growth. In simple terms, economic growth is seen as the driving force behind the demographic transition, so all we need in today’s poor countries is economic growth. That will bring population growth to an end.
The end point of the first demographic transition was thought to be an older stationary and stable population corresponding with replacement level fertility (a total fertility rate of approximately 2.1) and life expectancies of 70 years or more. Demographers thought that there would be a balance between crude birth and death rates, so the population would not grow unless natural increase was supplemented by immigration, which most thought would be unnecessary. They argued that this demographic transition would gradually encompass the world; nuclear couples everywhere would converge on a demographic ideal—two children for the most part.
There were two problems with this simplistic conceptualization of the demographic transition. First, nothing in either history or human behavior suggested that any society, let alone all societies, would converge on a pattern of marriage and reproduction that would stabilize population size. Second, starting with Thompson and continuing today, the demographic transition model has not been set within the broader context of the rising use of fossil fuels that has characterized the last two centuries or more, a revolution in energy availability that would prove to be unsustainable.
The second demographic transition. The second demographic transition, first described by Dirk van de Kaa in 1987, was a response to observed fertility rates in many European countries that were dropping well below replacement level. This model sees no such equilibrium between births and deaths as the end point of demographic transition. Rather, new developments in different societies have presented more varied arrangements of marriage and reproduction than were first imagined by demographers. Not only have we now observed sustained sub-replacement fertility in many places, we have also witnessed a variety of living arrangements other than marriage, the disconnection between marriage and procreation, and even depopulation in some cases, primarily among rich countries, from Japan and Germany to Russia and the Ukraine.
Because neoclassical economics depends on sustained growth (an oxymoron to anyone outside of economics), the thought of depopulation has created concern, if not outright horror, among numerous economists. At the same time, because they still believe that economic growth will bring population growth in poor countries under control, they worry not in the least about the demographic futures of places like Bangladesh, Pakistan, or Saudi Arabia.
The third demographic transition. The second demographic transition came about when assumptions of the first one, especially the assumption of an equilibrium between births and deaths, proved to be too simplistic. The second demographic transition introduced new ideas about marriage arrangements and reproduction and suggested that depopulation may occur in many rich countries in the years ahead. However, neither of these transition models gave any consideration to the broader world economic context within which they were set. A part of that context has been easy access to cheap fossil fuels and the rapid diffusion of industrialization.
Both the first and second demographic transitions assumed that mortality would decline to very low levels, leading to long life expectancies. They differed in their views of fertility. However, neither model considers that the historical period in which demographic transitions have occurred is one in which abundant and cheap fossil fuels resulted in substantial increases in productivity, both in agriculture and industry. With the demographic transition people were swept out of rural areas and agriculture into cities and industry, then into services, a pattern that continues today in numerous places.
Russia provides a glimpse of what we may recognize as the third demographic transition, one in which mortality rates rise again, bringing about not just an equilibrium in which population finally stabilizes but a period of depopulation that gradually encompasses much of the world. Nothing in either the first or second demographic transition models predicted what has happened in Russia, as is apparent in the figure below.
This third demographic transition, still preliminary at this point, will force us to focus on mortality, which will begin to rise as cheap oil disappears over the horizon. Signs of this are appearing regularly, as we see in the figure below, with its food price spikes and general upward trend in food prices since 2002.
Though many economists and others praise the “Chinese economic miracle,” few if any credit it in large part to the decision to initiate a one-child policy in 1979, a policy that has led to a current Chinese population that is about 400 million less than it would have been otherwise. Add those 400 million into China today and there would be no Chinese economic miracle to talk about. Had that Chinese lesson been followed three decades ago throughout the poor world, then chances of the poor countries reaching demographic stability and achieving better living standards would have been greatly improved.
Instead we continue to add more than 80 million people to the world each year, almost entirely to the poor countries, and economists keep ensuring them that all will be well in the long run because economic growth will save them from themselves. Since the United States consumes about a quarter of the world’s energy resources, with less than five percent of the world’s population, the promises of economists have always rung hollow. But they ring even more hollow today as Japan struggles with recovery from its devastating earthquake, tsunami, and nuclear disasters and unrest continues to spread throughout the North Africa and the Middle East.
We have to question the promise to the poor countries that economic growth will solve their demographic problems. That was not the case in China and going forward it will not be the case in most poor countries because the rising cost of fossil fuels will not be able to deliver the needed productivity increases. The Ponzi scheme of neoclassical economics, based on the faulty assumption that growth can continue forever, is edging toward its Bernie Madoff moment.
The third demographic transition model is based first on an assumption of the obvious: Population growth cannot continue forever. Beyond that, it assumes that the era of cheap fossil fuels has ended, no matter what effort is made to maintain it. That assumption is based on the fundamental concept that oil is both an extraordinary source of energy and finite in supply. In addition the model assumes that food production will decline worldwide as oil becomes more expensive. In turn that will lead to higher food prices, so feeding the poor will become ever more tenuous. This trend will be further exacerbated as rich countries, especially the United States, turn more to using food crops and cropland to produce liquid fuels to continue what James Howard Kunstler has dubbed “happy motoring.”
Needless to say, the third demographic transition will not only curtail population growth in the decades ahead, it will lead to depopulation as our numbers decline back toward more sustainable numbers. I doubt that Earth will see the 9.15 billion people that the United Nations projected in its medium variant for 2050; even the 7.96 billion in its low variant seems highly unlikely. After all, that is a billion more than we have today.