It is not as certain as night follows day but almost that when considering the future size of the 1 billion population of sub-Saharan Africa. It is destined to rise to at least 2 to 3 billion in 30 years’ time. Long before then it will almost certainly produce ethnic and religious wars and, probably suffer epidemic diseases of the Ebola or Dengue Fever variety. None of these, however, will bring population down with a bump.
The only way that average family size can be brought down from well over four children per family to a replacement two, or fewer, is when peasants leave the land and its highly macho culture and live in cities which have a sufficiently intrinsic economy in which there may be low level jobs and some sort of minimum welfare — even if it’s only free electricity for television.
Such cities are relatively lacking in sub-Saharan Africa. Meanwhile in 30 years’ time, at least 300 million people in the coastal provinces of China who have not yet reached protein sufficiency in their diets, and a further 600 million people of the interior of China who hardly have any protein at all will be increasing their demand for nutritious food.
Assuming that the Chinese government is successful in its aims to bring all its people up to a reasonable standard of living — albeit not quite middle class — then those 900 million people will require the equivalent of 9,000 million people’s grain as protein feedstock for feeding sufficient beef, pork, sheep, chicken and fish.
Given that the rest of world will top out at about 11 or 12 billion people then that leaves only a fraction (12 – 9 = 3 billion) of today’s and tomorrow’s population that will survive without starvation to some extent or lack of adequate nutrition. Nature will have its way even in our own species.