Are you worried about overpopulation?

A dear friend is very concerned that global overpopulation is making sustainable resource management impossible. A current example is the California drought and water crisis. Because this subject is definitely not intuitive, I thought I would share some resources that I outlined by email:

Regarding your sincere population worries – here are some possibly useful resources. First, the one hour BBC-produced talk by Swedish demographer Hans Rosling is an friendly introduction to  population dynamics BBC “Overpopulated”.

The fact that BBC funded such an expensively-produced mini-documentary reflects the reality that many people continue to accept the 1960s perspective voiced by Paul Erlich and The Club of Rome. This Malthusian view was what I believed through the 1990s. It was only when I had time to study current population research that I realized I was very out of date.

For a more in-depth, but still easy to follow lecture, see mathematical biologist Joel Cohen’s Floating University segment Malthus Miffed. I think it would be difficult to digest Dr. Cohen and still be frightened about runaway long term population growth.

That said, we also know very well how to make population growth a problem again. If we hobble the engine of economic growth – especially the improvement of the incomes of the very poor in Africa and Asia, then we could blow through the 9 Billion U.N. population forecast (plus 2.5 Billion from 2014).

It could happen – consider how badly the 2008 global financial crisis was handled by politicians and central bankers. “Never underestimate a politician”. But even with the below trend growth that we observe in the USA and EU, the Bottom Two Billion is transitioning out of subsistence farming to urban progress. Continuing that progress is essential to the forecasts of better health leading to falling family sizes.

For more well-written background on the subject please read the recent survey article by Stanford’s Martin Lewis: Population Bomb? So Wrong. E.g., did you know that India and America fall into the same (TFR of 2 to 3) fertility bucket? Excerpt:

India’s declining fertility rate, now only slightly higher than that of the United States, is part of a global trend of lower population growth. Yet the media and many educated Americans have entirely missed this major development, instead sticking to erroneous perceptions about inexorable global population growth that continue to fuel panicked rhetoric about everything from environmental degradation and immigration to food and resource scarcity.

In a recent exercise, most of my students believed that India’s total fertility rate (TFR) was twice that of the United States. Many of my colleagues believed the same. In actuality, it is only 2.5, barely above the estimated U.S. rate of 2.1 in 2011, and essentially the replacement level. (A more recent study now pegs U.S. fertility at 1.93.) Still, from a global perspective, India and the United States fall in the same general fertility category, as can be seen in the map below.

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In today’s world, high fertility rates are increasingly confined to tropical Africa. Birthrates in most so-called Third World countries have dropped precipitously, and some are now well below the replacement rate. Chile (1.85), Brazil (1.81), and Thailand (1.56) now have lower birthrates than France (2.0), Norway (1.95), and Sweden (1.98).

To be sure, moderately elevated fertility is still a problem in several densely populated countries of Asia and Latin America, such as the Philippines (3.1) and Guatemala (3.92).

Click to embiggen

I highly recommend a careful read of the Martin Lewis essay. E.g., the surprising correlation of TV viewing with TFR (is it causation or coincidence?).

So, that’s a summary of the perspective of academics who make a living worrying about population growth. But we also know very well how to make population growth a problem again. One way is to destroy the engine of economic growth – especially the ongoing improvement of the incomes of the very poor in Africa and Asia. If we did that, then we could blow through the U.N. 2050 forecast of 9 to 10B population.

It could happen – consider how badly the 2008 global financial crisis was handled by politicians and central bankers. “Never underestimate a politician”. But even with the below trend growth that we observe in the USA and EU, the Bottom Billion is transitioning out of subsistence farming to urban progress. That progress is essential to the forecasts of better health leading to falling family sizes.

Another way is to allow climate change to develop so much momentum that there are no feasible mitigation or adaption strategies. That is sure to diminish incomes & health in the vulnerable populations. And those are the key drivers of the population turnaround.

Dear reader, if you know of other quality resources please provide the links. And especially please mention any peer-reviewed work that contradicts the consensus view reflected by professors Rosling,  Cohen and Lewis.

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