Africa's population growth figures are staggering. The continent had a fertility rate of 5.4 children per woman between 2005 and 2010 - double that of any other region - and it is projected to decline only to 3.2 by 2050, still higher than other regions (the rate is under 2.5 in Asia, and below 2 in East Asia).
This will more than double Africa's current population of one billion to 2.1 billion by 2050, and quadruple it to 3.9 billion by 2100, according to the population division of the United Nations Department of Economic & Social Affairs (UNDESA). Half of projected population growth until 2050 will be in sub-Saharan Africa.
What does all of this mean for African development?
Raw population size is not, in itself, good or bad. What matters is how the structure of the population changes.
Strong economic performance in Asia over the last half century has been in part due to a 'demographic dividend' - the process by which fertility rates begin falling, meaning a large group of young people move from being dependents to being of working age, without a similarly large group being born 'behind' them. If the young population entering working age receive decent education, and are able to find employment and save money, fertility rates fall further.
Parts of East Asia and India have initiated that transition successfully, but what is the likelihood of African economies following a similar path?
The data is not too encouraging. While there are indications that the youngest segment of the African population will start to shrink in number, the two 'ifs' of the demographic dividend are far from assumed. Available work and high educational attainment are both crucial to enable demographic change to boost development. But formal job creation is stagnant across the continent, educational outcomes are still quite poor and savings rates are too low.
In Asia, fertility started to decline in the 1950s, which meant rising numbers of workers per dependent. This is happening in sub-SaharanAfricatoo, but later and more slowly. With that in mind, population growth in Africa could prove a burden rather than a boon.
There are positive examples in the African context, though. Health outcomes are improving. Improved health outcomes meant women did not feel compelled to have as many children. Contraception availability rose from 28pc in 1984 to 53pc in 2007.
Improved educational access, including exclusion of school fees for the poorest, raised the number of girls achieving education. All of these interventions combined worked to reduce the fertility rate.
The biggest downside risk to population growth, if other structural changes do not move in step, is growing food insecurity. There are two solutions to the food security problem, and both look elusive.
The first is to expand the acreage that is harvested for agriculture. But a conversion area the size of Germany,France and the UK combined would be needed to achieve this in Africa- with clear ramifications for conflict, land rights, water, carbon emissions and biodiversity. The second is intensification - increasing yields on existing farmlands. But Africa would require a yield growth in cereals 50 percent higher than the global average over the last 40 years.
Some regions look better prepared to cope with the food demands of a rising population than others. But, the overall picture is bleak.
High fertility rates are not inevitable in poor countries. Peru, Uzbekistan, and Bangladesh all reduced fertility rates of just under seven in 1960 to around 2.5 by 2010, through voluntary family planning programs, increases in education, and improvements in child survival - and all three were classified as poor in 2011, ranking 87th, 139th, and 166th out of over 180 countries in per capita income.
It may be cultural norms, rather than poverty, which obstruct progress to a lower fertility rate. Patriarchal cultures display persistently high fertility rates as a result of social norms prejudiced against women.
Africa's success of the last decade has been real, and the signs are everywhere to see. But in the face of a population growing this quickly, those gains will need to be accelerated if the continent is to avoid simply treading water, or falling backwards.
Adam Green Is Senior Reporter With the Financial Times. This Commentary First Appeared On African Arguments.