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. Continue reading