While climate change and food shortages are problems in and of themselves, they are also partially byproducts of an underlying cause: population growth. More people in the world equals more demand and greater impact.
So, it’s not inconsequential that the latest population estimates are much higher than previously thought. Two billion people higher, in fact. Instead of 9 billion people in the world by 2100, there could now be more than 11 billion.
The forecast comes from the University of Washington and the United Nations, whose researchers explain their work in a recent Science journal paper.
“The consensus over the past 20 years or so was that world population, which is currently around 7 billion, would go up to 9 billion and level off or probably decline,” says Adrian Raftery, a University of Washington professor, in a press release. “We found there’s a 70% probability the world population will not stabilize this century. Population, which had sort of fallen off the world’s agenda, remains a very important issue.”
The estimates are based on mortality and fertility rates, migration, and other factors, and rely more on statistics–as opposed to opinion–than previous forecasts. They also give percentage probabilities, rather than scenarios for what might happen. By 2100, there’s an 80% likelihood that the global population will be between 9.6 billion and 12.3 billion, the research shows.
Sub-Saharan Africa is set to see the greatest increases. As a whole, Africa is expected to go from having roughly 1 billion people today to 4 billion by the end of the century. Other continents are likely to have more constant numbers, with population even declining in parts of Europe.
But nothing is set in stone. Greater access to contraceptives and more education of girls and young women could halt the population surge, Raftery says.