hope for nature and humanity

In grad school I came across The Limits to Growth - a book by the Club of Rome. Basically a report on computer simulations of exponential population growth and limits of the carrying capacity of the planet for a number of resources.  It struck me as bleak and depressing suggesting zero population growth was our only path out. I was curious about their model and found issues with the underlying data set and models. It wasn’t possible to describe population growth trends with simple exponentials. Something else was going on. They admitted some issues, but swept it under the rug sort of claiming “correct” data would fit their model. It began to slowly eat at me.

 

A few years later  I found myself traveling to Princeton regularly as part of a collaboration. It’s a great place to run into people and ask questions.  Eventually I found some demographers and learned at their feet. They weren’t terribly impressed by the book. They freely admitted there were serious issues, some of which may be existential threats.  At the same time there were some extremely positive trends.. Instead of simple exponential models there are periods of development with different population dynamics.  At first I had a my doubts, but their models fit the available data and fit some emerging trends much better than the CoR report.  There are a  variety of models, but they mostly boil down to three main stages.

 

The first is a period where the death rate is very close to the birth rate - sometimes exceeding it, sometimes falling short. Humanity was scattered around the globe and regions would fade in and out.  Eventually with trading centers becoming stable with very low population growth. The death rates were enormous.. for a family to continue to the next generation you generally needed more than six children.

 

The second stage is marked by the introduction of sanitation and successful disease prevention. Death rates drop dramatically, but people still maintained extremely high fertility rates.   The sanitation and medical knowledge is quickly communicated to populations at a similar stage. This results in enormous population spikes.  In the US the core part of this stage was from about 1920 to 1970.

 

The third stage sees women gaining education, opportunity and control over their bodies and fertility. Incomes are rising and families begin to focus putting more into fewer children. The fertility rate drops .. often dramatically.  Think Japan and parts of Europe. 

 

Different regions of the world go through these at different times and rates. One of the huge drivers for the second and third stages is urbanization. At first it  seemed counterintuitive, but when you talk to demographers and read their papers it becomes clear the growth of cities is the rocket fuel that enables the rest.

 

About fifteen years ago I organized a small conference on this at Aspen. I left with great hope and enthusiasm believing that lowering some of the other potentially existential threats would only make this process easier. In my mind the immediate low hanging fruit was working on global warming. It could have been, but I didn’t understand the inertia and control of the fossil fuel industry.

 

I could go on and on about these demographic trends and had intended to, but it would be book length and others are more expert in the area. I may talk about it in the future. The next stage is cloudy I can argue for at least four very different paths .. some of them pretty awful. But I recently came across a nice discussion of the saving nature piece..

 

Now for the good part.  Sean Carroll of Caltech interviews Joe Walston - the senior VP of Field Conservation at the Wildlife Conservation Society.  Joe offers a better summary of these issues than I could in an hour of writing  It's a bit over an hour long, but worth it if you have any interest in demographic trends, why they happen and where they could go.

 

Finally it's interesting these trends appear to be society independent.  We like to think how different we are, but in many ways, for good and bad, we're the same.  I find that comforting.

 

 

 

Comments

[Jean Russell]

Thank you Steve. This is marvelous. In my work history, we discussed this phenomenon as "pig in a python" because of the shape of the curve. It reminds me of the "hat" in The Little Prince. The upside is the population rate can decline. The sad news is the social tensions that arise from migration into areas of lower population rates (and their affiliated rise in standard of living) as a result of climate change and the resulting political upheaval.