The world’s population will keep growing and by 2100 it could reach 12.3 billion from the current 7 billion, according to the latest predictions.
The experts behind the new findings warned that population should be put back on the world’s agenda after previous forecasts put the total at the end of the century at about two billion fewer.
Scientists from the University of Washington and the United Nations used advanced statistical models to make more accurate predictions. They said there was an 80 per cent probability that the population in 2100 would be between 9.6 billion and 12.3 billion.
“The consensus over the past 20 years or so was that world population would go up to nine billion and level off or probably decline,” said the author of the findings, Adrian Raftery, a professor of statistics and sociology at the University of Washington.
“We found there’s a 70 per cent probability the world population will not stabilise this century. Population, which had sort of fallen off the world’s agenda, remains a very important issue.” A rising population could exacerbate issues such as climate change, disease and poverty, he added.
The paper, published online in the journal Science, largely supports UN population projections from last year, but adds a new dimension, according to Patrick Gerland, a demographer at the UN. “Earlier projections were strictly based on scenarios, so there was no uncertainty,” he said. “This work provides a more statistically driven assessment that allows us to quantify the predictions and offer a confidence interval that could be useful in planning.”
Population projection is a notoriously difficult science, requiring statisticians to take into account many variables, including birth and death rates.
Predictions for the population in the year 2000, for example, fluctuated over the years, peaking at 6.49 billion in 1973 and going as low as 6.06 billion in 1998. The current estimate is that there were 6.13 billion humans alive that year.
This is the first UN population report to use modern statistics — known as Bayesian statistics — which combine all available information to generate better predictions. The majority of the anticipated growth is expected to be in Africa, where the population could quadruple from about one billion today.
The growth is largely because birth rates in sub-Saharan Africa have not been decreasing as fast as expected, meaning that there is an 80 per cent chance that by 2100, the population in Africa will be between 3.5 and 5.1 billion people. Other regions are not expected to experience as much change, with the population of Asia, at 4.4 billion, projected to peak at five billion around the middle of the century before it begins to decline. Populations in North America, Europe, and Latin America and the Caribbean are expected to remain below one billion.
Dr Raftery said the previous method of estimating future population was too imprecise. “This paper brings together the research from the past seven years, and also brings in recent data,” he said. “We can answer questions about future population growth using standard principles of statistical inference, which has never really been done before.” Population growth can be controlled by investing more in education and family planning programmes, the researchers said.
