A few years ago in Kenya, a taxi driver and I were remarking on the endless shambas—tin-roofed farmhouses on impossibly small plots of land—sprawling out from Nairobi all the way across the Great Rift Valley to Lake Nakura. Kenya’s population had quintupled in the driver’s lifetime, from 8.1 million people in 1960 to 44.4 million today, and the consequences were all around us. He pointed out places where he could remember seeing rhinos, hippos, elephants, and other wildlife.
All gone now.
It’s the sort of thing that makes conservation biologists foresee an Africa without wildlife. An analysis just out in the journal Science suggests that the problem may be worse than anyone has imagined, with the population in Africa increasing from a billion people today to as much as 5.7 billion by 2100.
Past analyses have generally concluded that the total world population would increase from 7.2 billion today to about 9.6 billion mid-century and then stabilize or even slowly decline. But the new analysis, from a global consortium of demographers and the Population Division of the United Nations, finds “little prospect of an end to world population growth in this century.” Instead, the Earth will somehow need to feed and accommodate 11 or 12 billion people by 2100, with much of the increase happening in sub-Saharan Africa.
That conclusion is surprising, because the birth rate continues to decline worldwide and in Africa. But the decline in Africa is happening at only a quarter of the rate seen “in Asia and Latin America in the 1970s, when they were at a comparable stage” in the transition to smaller families, according to the new analysis. In some African countries, the rate of decline has stalled over the last 15 years, according to John Wilmoth, the report’s coauthor and director of the U.N. Population Division.
Among possible factors behind the slowdown: The desired family size reported in Africa was larger to start with (at 6.5 children), requiring a more dramatic shift in expectations to get to replacement level (2.1 children). The level of socioeconomic development in those countries has lagged behind even some Asian countries decades ago. Delivery of family planning programs needs to be better supported and more culturally sensitive. Wilmoth noted that the stalled fertility decline has a compounding effect. Not only do families today have more children, “but those children have more grandchildren, and so on into the future.”
In Nigeria alone the population is now estimated to increase as much as fivefold, from 160 million today to as much as 914 million people—in shouting distance of a billion—by 2100, according to the new analysis. That’s bad news for those in what is already one of the most notoriously chaotic nations in the world, one struggling with both an Ebola outbreak and an Islamic revolt. It’s also terrible news for wildlife in a nation that has already eradicated cheetahs, pygmy hippos, black rhinos, giant elands, and a menagerie of other species.
“Human pressure is already so high in Nigeria that there is almost no wildlife left outside of national parks,” Andrew Dunn, Nigeria country director for the Wildlife Conservation Society, said in an email. The increasing human population, he said, will require protecting national parks with “greater investment, stronger political will, and most important of all, ensuring that surrounding communities benefit in some way from the presence of the national parks.” Otherwise, “wildlife will not survive till 2100.”
Also on the list of countries facing major increases are Tanzania (due to quintuple its population by 2100) and Kenya (on track to quadruple), where rapidly dwindling wildlife populations have made tourism a mainstay of the economies, up to now.
The new study provides a grim list of likely challenges from a rapidly increasing population, including depletion of natural resources and rising environmental pollution; unemployment, low wages, and poverty; high maternal and child mortality; lagging investments in health, education, and infrastructure; and increasing crime and social unrest.
By failing to reduce the rate of population growth, countries such as Nigeria, Kenya, and Tanzania also miss out on “a potential long-lasting demographic dividend,” according to the report.
Adrian Raftery, a coauthor of the study and a demographer at the University of Washington, explains it this way: When fertility goes down, that means fewer children in a particular cohort. As the larger population just above it enter their productive years in the workforce, they have fewer kids to support and a relatively small number of elderly. Thus “the potential to have a very strong economy,” he said. “Usually the effect will last a working life, 30 years or so. In Ireland, for example, fertility declined rapidly after 1960, and that was a big factor in the Celtic Tiger economy, and also in the rapid recovery” after the 2008 recession.
“African economies could reap the same benefit,” Raftery added, if they get serious about more effective family planning programs now. (Wilmoth noted that governments in Ethiopia, Rwanda, and Malawi have already begun to put more emphasis on reproductive health and are seeing increased uptake of contraception.)
Apart from the African results, the new study is important because it corrects flaws in past U.N. population estimates, which often came under attack for failing to take realistic account of probabilities. For instance, the U.N. used to provide high and low population projections simply by taking a country’s total fertility rate per woman and adding or subtracting half a child. While that half-child difference might have applied in a given country or year, it would hardly have applied to all countries and all years. The new statistical model “takes better account of fluctuations over time of fertility and mortality,” said Raftery.
He developed some of the new methodologies, curiously, while calculating whale population sizes for the International Whaling Commission and trying to project populations based on fragmentary data. The methods used for whales, which are also big, long-lived mammals, turned out to apply to humans. Whales could thus indirectly do us the great service of encouraging support for family planning.
“The bottom line I hope people will take away from our work,” said Raftery, “is that population needs to go back to the top of people’s agenda. It’s going to drive a lot of other issues. So it should be a priority.”
Apart from lobbying governments to make that happen, Wilmoth added that individuals should look to the flip side of the population debate: “A lot of this has to do with how we live, what we consume, how we produce the goods we consume, and how we dispose of them, and the energy we use.”
If we want to have a world worth living in—and for most people that means a world with room for wildlife to live alongside us—we are going to have to come up with new ideas, new behaviors, and new designs for landscapes and for living.
And with the nightmarish prospect of a billion-person Nigeria in sight, we are going to need them pretty damned quick.