In much of the world populations are already stabilizing or contracting, but in Africa a population explosion is taking place, which, based on the UN’s medium fertility model, could see the population of Africa increase from 800 million in 2000 to 4.38 billion in 2100; an additional 3.576 billion people over the century. It is this very large projected growth in Africa’s population, combined with the stress of climate change and conflict on that continent, which will be the main driver of (attempted) illegal migration into Europe in the 21st century. In response Europe will likely become a dark fortress, denying entry.
The current pressures for mass migration from Africa include war, poverty, poor governance, corruption, crime, famine (see https://theworldincrisis.com/un-aid-chief-urges-global-action-as-starvation-famine-loom-for-20-million-across-four-countries/), terrorism, and climate change.
Large numbers of Africans are malnourished, and the WHO states that malnutrition is estimated to contribute to more than one third of all child deaths, although it is rarely listed as the direct cause. In Africa, about 24 percent of children are underweight and 35 percent are stunted.
(c) Andrew Palmer, 2017 (do not reproduce without permission).
 http://www.who.int/maternal_child_adolescent/topics/child/malnutrition/en/, accessed 29 June 2016
UN Projections of the Increase in Africa’s population over the 21st century