The "base case" scenario described in the 2004 edition of "The Limits to Growth", an update of the original study sponsored by the Club of Rome and published in 1972. Note how the world's population is supposed to start declining some years after the peaking of the world's economy. We are not yet seeing this decline at the global level, but we may be seeing it in some specific regions of the world; in particular in Italy.
More and more data are accumulating to disprove the legend of the "mistakes" that has been accompanying the study titled "The Limits to Growth" (LTG). For instance, Graham Turner has shown how the historical data for the world's economy have been following rather closely the curves of the "base case" scenario presented in 1972. But the fact that this scenario has been working well up to the beginning of the 21st century doesn't mean it will keep working in the same way in the future. The base case scenario describes a worldwide economic collapse that should start at some moment during the first two-three decades of the century. Clearly, the world's economy has not collapsed, so far, even though it may be argued that it is giving out ominous signs that it is starting to do just that. But, we can't yet prove that the base case scenario was right.
Yet, the LTG collapse scenario is an average over the whole world and we may imagine that some sections of the world's economy should collapse earlier, and some later. And, indeed, it appears that some local economies are collapsing right now. It may be that a country like Italy is already well advanced in this process, so that we shouldn't be not just seeing the decline of its GdP, but also the start of an irreversible population decline. And some recent data indicate that this is exactly the case: the LTG base case scenario is playing out in Italy, and probably not just in Italy.
So, let's try to make a qualitative comparison of the LTG scenario and the actual data for Italy. First of all, the scenario shows how the consumption of natural resources is supposed to reach a maximum and then decline, followed by a similar trajectory for the economic output. We are already well past this point in Italy. As you can see in the figure below, from a previous post on Cassandra's legacy, Italy's consumption of hydrocarbon fuels (by far its main source of energy) peaked in 2005, followed by the peak in the GdP in 2008. Considering that the GdP is a measure of the overall economic output of a country, we can take it as proportional to the parameters that were indicated as the industrial and agricultural production in the LTG study (the data for 2015 indicate a small GdP increase for Italy, but that changes little to the overall trend).
So, we may say that the base case LTG scenario has been playing out in Italy in terms of the behavior of the economy of the country. But, if this is the case, at some point we should expect another curve of the scenario to peak and start declining: the population curve. And, indeed, we seem to be seeing exactly that. Here are the most recent data from the Italian statistical agency, ISTAT
You can see the remarkable jumping up in the mortality rate for 2015: it corresponds to 165,00 more deaths than births. Despite the influx of immigrants, Italy has lost 139,000 residents in 2015; not a large loss (0.23%) but it is significant. And it had never happened during the past few decades. Also, Italy sees for the first time in decades a reduction in the life expectancy at birth (from 80.3 years to 80.1 years for males and from 85 years to 84.7 years for females).
What have been the causes of this population decline? There are several, and the torrid summer of 2015 has surely played a role in killing more old people than usual, as you can see in the figure below (again from ISTAT)
Then, other causes have been proposed; the general aging of the population, the economic crisis, the worsening diet, pollution, the higher costs of medical care, and more. But the point, here, is not to discuss these various causes, most of which probably had a role in the decline. The model doesn't describe the details of the process, nor it is detailed to the point of considering different age cohorts. It is a quantitative description of a relatively simple phenomenon: a population under stress because of reduced resource availability and pollution will react by an increasing number of deaths in its weakest age groups: the elderly ones. And this is exactly what we are seeing in Italy: a decline in population following the decline in GdP.
Of course, we only have data for one year and we cannot say if what we are seeing is a long-term trend or just a statistical fluctuation. Yet, it is hard not to think that the degrading economic, social conditions in Italy, as well as the degradation of the ecosystem, are not taking their toll on the population. And that we are indeed seeing the LTG scenarios playing out.