Mass immigration has turned into a crisis that places a big burden on first world countries which aim to maintain their humanitarian standards. To reduce the streams of refugees, European nations have made deals with Turkish president annex dictator Erdogan, who promises to reduce the influx in exchange for visa free travel for Turkish citizens and other rewards.

There is good reason however, to believe that the streams will grow drastically in the decades ahead. To understand why, take a look at some of the below graphs:

Projected agricultural productivity change between 2003 and 2080

As can be seen, Europe and North America are projected to witness an increase in agricultural yields. For Africa and South Asia, the outcome is projected to be far more catastrophic instead. It’s thought that the viking era was caused by overpopulation in Scandinavia. It’s also thought that a temperature drop in Northern Europe led to the Germanic invasions of the Roman empire. This is what tends to happen to populations that suddenly find themselves above carrying capacity, as a result of a sudden decrease in agricultural productivity of their land.

Youth bulge

Who leaves his country of origin in search of distant lands to colonize? Generally speaking, young men with poor prospects at home are most inclined to migrate to distant lands. Where do most of the world’s young people live? In third world countries.

The map above shows the percentage of the population aged beneath 15 years in 2013. By now most of this cohort is in their twenties. The fertility rate in most of the Middle East and North Africa has dropped very rapidly in recent years, but this has no effect of course on young people who have already been born. If the fertility rate in these nations has dropped because of overpopulation, the current youth bulge in these nations will have to deal with the consequences of ecological overshoot.

Population explosion in sub-Saharan Africa

Although great progress has been made in addressing population growth in the Middle East and Northern Africa, in Sub-Saharan Africa, we have been less than successful. In fact, many African countries have seen stable high fertility rates for decades.

In the period of 1950-1955, the fertility rate in Uganda was estimated at 6.9 children. In 1985-1990, the fertility rate was actually higher, at 7.1 children per women. By 2010-2015, the fertility rate has dropped to 6.38 children per woman. In the meantime however, the infant mortality rate dropped from 116 per 1000, to 61 per 1000, meaning that more of these children grow up to reach the age of reproduction themselves.

In Nigeria, the fertility rate is 6.01 children per woman, hardly any different from the peak fertility rate of 6.76 children decades ago. In the last period of five years, the fertility rate went down by 0.04 children. At this pace, a replacement fertility rate that would stabilize the Nigerian population would be reached 500 years from now.

There are however even worse situations found in some other African nations. In Congo, the fertility rate was estimated at 6.3 in 2007/2008. In 2013/2014, the fertility rate was estimated at 6.6 children per woman. In other words, fertility had gone up, rather than declined.

What causes this? Lack of access to contraception is one problem for certain regions, but a large part of the problem that’s taboo to discuss is the cultural factors that cause women to give birth to so many children. In parts of Nigeria, 81% of women desire more than four children. Eight percent of the women desire more than fifteen children.

Contrast this with Europe. In Western Germany in 2004, 16.6% of women desired no children. Just 3.7% of the women desire more than four children. The mean desired fertility rate was 1.73 in Western Germany, which is a desired fertility rate below replacement level. It should be clear that the conventional feel-good solution of providing contraception to women who desire contraception but have no access that has become established liberal wisdom is not going to be enough to solve our problem.

To make matters worse, desired fertility levels differ enormously between different socioeconomic groups in these nations. Muslims in Kenya have a desired fertility rate of 6.3, compared to 3.8 for Christians. Desired fertility rates are also much higher for poorer citizens.

It’s often thought that economic development reduces desired fertility rates, but this is not entirely clear. Some studies suggest that this has cause and effect backwards, that declining fertility rates actually led to economic development as nations temporarily ended up in a situation with few elderly and few children who need to be taken care of.

Interestingly, although quite some progress was made in reducing African fertility until the 90’s, the economic development in Africa that occurred since the 1990’s has not led to a further decline in fertility. Nigerian GDP per capita grew enormously since 2000 and continues to grow rapidly today. Fertility rates did not decline significantly as a consequence however. If anything, economic growth in Sub-Saharan Africa allows these nations to maintain high fertility rates that would otherwise lead to a Malthusian catastrophe.

There exists no consensus on what causes the high desired African fertility rates. If we’re lucky, desired high fertility rates are largely a product of the high fertility rates women observe around them. African women who actually have more than eight children tend to be more ambivalent about their high fertility. Providing access to contraception would thus lead to a reduction in desired fertility rates, which would lead to more demand for contraception, in a positive feedback loop.

More likely however, entrenched cultural factors play a role. It’s observed in multicultural societies around the world, that Muslims have higher fertility rates than Christians, Atheists and Hindus. More devout religious observers also tend to desire higher fertility rates. Most worrisome of all perhaps is the observation that tribal conflict between different ethnic groups leads to higher desired fertility rates in some nations. Palestinian authorities in Gaza were opposed to family planning for this reason. A look at maps of global cultural diversity shows a rough trend of lower fertility rates in less culturally diverse nations:

Finally, most problematic perhaps would be the possibility that genetic factors play a role in the high desired fertility rates in sub-Saharan Africa. It’s observed around the world that African girls enter puberty earlier than European girls, who enter puberty earlier than East Asian girls. Doctors have noticed that African and Aboriginal babies seem to mature earlier, at an age where Native American and Asian babies are still very helpless.

If children from certain ethnic groups innately require far more parental investment than children from other ethnic groups, it would make sense that women from some ethnic groups are more interested in birth spacing and reducing their fertility rates than other groups. As a consequence, we may find that addressing population growth in sub-Saharan Africa will be much more difficult than it proved to be in other places.