[Part I; Part II; Part III; Part IV; Part V; Appendix; Single page]

by David Severa

And finally, a quick bonus dialogue in response to this question from Tumblr user Wirehead Wannabe:

Highly recommend this series regardless of your position on the issue.

To Restrictes and Openo: you’ve talked a bit about fertility rates, but only those of people currently living in developed nations. How does open immigration affect total population growth rates? Do countries tend to have a “carrying capacity?”

The scenario I’m worried about is one in which an unpleasant to live in yet fecund nations keeps churning out babies that are doomed to a life of suffering if we don’t let them into our walled gardens, and in which any people who are removed from that situation are replaced by more suffering people that would not have been born if the original people had stayed. So letting people in never actually results in decreased suffering in the donor countries. (I hope that was written clearly enough.)

• RESTRICTES: This is similar to my worry that emigration might worsen conditions in poor countries, which might turn an initial wave of emigration into an unending one.
• OPENO: Yes, but I think I showed that there was no strong evidence of that sort of negative effect. In fact, emigration likely raised wages in at least some poor countries, which presumably could lead to better education, etc. and thus lower fertility. And in fact essentially every country on Earth has seen a significant drop in fertility over the last few decades:

• OPENO: Look at Mexico. About 12% of the population has emigrated, and yet the fertility rate has dropped from 6.8 in the 1960s to 2.2 today. And it’s still dropping, albeit at a slower rate. Similar drops have happened in most poorer countries, whether or not they’ve seen significant emigration. Obviously Africa is the region that still stands out (and Afghanistan and Timor-Leste), but that seems to be entirely a function of poverty rather than emigration. Africa is developing, however haltingly, and I would expect fertility to match the rest of the world sometime within the coming decades. If that happens, there really won’t be anywhere left for the fear of unending, ever-growing hordes to be realized.
• RESTRICTES: A drop from 6 children per woman a few decades from now is cold comfort. That could still lead to massive population growth. The UN projects that Africa’s population could quadruple by 2100.
• OPENO: True, but letting immigrants in won’t worsen the problem, which was the original question. (And I would take the under on those projections.) And if immigrants acculturate at all to their new country, then we would expect immigration to lower worldwide population growth, as young people keep moving to low fertility regions. I’ve already mentioned that Hispanic fertility has been converging to the American average. Also, for instance, Pakistani fertility is lower in the UK than in Pakistan, and both are dropping.
• RESTRICTES: But isn’t that massive growth in Africa reason enough to be concerned, even if overall fertility is in fact dropping? Maybe population growth will resolve itself in the 2100s, but that’s a long time from now. And given how connected the world is now, surely it’s just going to become easier for Africans to leave in the 10s or even 100s of millions. Four billion people would surely precipitate an environmental catastrophe worth fleeing.
• OPENO: Maybe, but I’m not sure. Remember that Africa’s population density is actually very low, even excluding the Sahara. (There are fewer people in all of Africa than in India.) A quadrupling of population would mean that Africa’s population density would equal China’s today, which is high but manageable. And African countries are often using cheaper, lower-yield agriculture today because population density is so low that they can afford to. What that means is that Africa has, even ignoring future improvements in agriculture, a large untapped capacity for higher productivity. Migration may increase because it becomes easier, but probably not due to a crisis in Africa.
• RESTRICTES: Surely there could be, say, water crises in parts of Africa, or crises due to climate change. You don’t need all of Africa to be a mess for significant emigration. Climate change may cause lower rainfall, more water loss, and worse droughts in Africa.
• OPENO: That is possible, and perhaps it’s the biggest potential problem facing Africa. But these problems intersect with social and technological changes in hard to predict ways. How much of Africa’s population will be farming decades from now? Will we develop new, more drought-resistant crops? If African agriculture becomes less productive, will Africans be able to make other exports to buy food from abroad? If they do, then there won’t necessarily be such a huge problem. You can’t consider this in isolation. It doesn’t make much sense to consider the carrying capacity of a single country. What is the carrying capacity of Singapore? There are limits – for instance there simply might not be enough water in the American Southwest for everybody to drink if the population keeps growing, and it isn’t feasible to haul water all the way from the Great Lakes to Phoenix. But other than water, most goods are easy to transport in sufficient quantities, as long as you can produce something worth trading. So a richer, more diversified Africa could withstand climate change, but it’s not guaranteed.
• RESTRICTES: It does, however, make sense to speak of a global carrying capacity.
• OPENO: With the caveat that there’s no one number of people the Earth can support, it depends on their lifestyle and how efficient their technology is.
• RESTRICTES: Yes, but I’m still thinking about climate change. Immigrants to the US produce four times the carbon emissions than they would have in their home countries. It’s true that poor countries are polluting more as they develop, but immigration to rich countries is accelerating that process considerably. Per capita carbon emissions in the developed world have plateaued or even dropped, but population growth counterbalances that. And of course, in general, richer people will use more resources of all types. Immigration is functionally equivalent to development and we haven’t figured out how to do that sustainably.
• OPENO: True, but is a higher carbon footprint a cost worth paying, considering all the benefits of modernity? I’m inclined to think so, but it’s a difficult question. In any case, even with more immigration, the problem of how to reduce carbon emissions remains the same.
• RESTRICTES: Even if the solution to the problem is the same regardless of immigration, immigration can still be worsening the problem.

Next: The demographics of Brexit and then the dialogue on moral realism

(Source for header image)