NEW YORK, New York - The world's population will surge past nine billion before 2050 and reach 10.1 billion by the end of the century if current fertility rates continue, according to United Nations figures released Tuesday.
Today's world population is currently close to seven billion, increasing by the second, and is projected to surpass seven billion towards the end of this year.
Today, 42 percent of the world's population lives in low-fertility countries, that is, countries where women are not having enough children to ensure that, on average, each woman is replaced by a daughter who survives to the age of procreation.
Another 40 percent lives in intermediate-fertility countries where each woman is having, on average, between 1 and 1.5 daughters, and the remaining 18 percent lives in high-fertility countries where the average woman has more than 1.5 daughters.
Most of the increase will come from high fertility countries, mainly in sub-Saharan Africa but also in some nations in Asia, Oceania and Latin America, the UN data shows.
High-fertility countries are mostly concentrated in Africa - 39 out of the 55 countries in the continent have high fertility - but there are also nine in Asia, six in Oceania and four in Latin America.
Three-quarters of the population living in the intermediate-fertility countries is located in India, the United States, Indonesia, Bangladesh, Mexico and Egypt, in order of population size, the data shows.
Low-fertility countries include all countries in Europe except Iceland and Ireland, 19 out of the 51 in Asia, 14 out of the 39 in the Americas, two in Africa, Mauritius and Tunisia, and one in Oceania, Australia.
China, Brazil, the Russian Federation, Japan, Viet Nam, Germany, the Islamic Republic of Iran, Thailand and France, in order of population size, account for 75 percent of the population living in low-fertility countries.
Prepared by the Population Division at the UN's Department of Economic and Social Affairs, "The 2010 Revision of World Population Prospects" shows that a small variation in fertility could lead to major long-term differences in the size of the global population.
Based on the medium projection, the number of people in the world should pass eight billion in 2023, nine billion by 2041 and then 10 billion at some point after 2081.
But a small increase in fertility could mean a global population of as much as 15.8 billion by 2100, while a small decrease could result in an eventual overall decline in population to 6.2 billion by the end of the century, according to the UN agency.
Hania Zlotnik, director of the Population Division, told journalists at a news conference at UN Headquarters in New York that the populations of many countries are ageing and will continue to do so as their fertility rates decline.
The population of countries classed as low-fertility or intermediate-fertility - including China, Russia and many countries in Europe - would thus peak well before the end of the century, she said.
Asked whether Japan and the Russian Federation, where the populations are forecast to decline, would be joined by other countries, Zlotnik said her office is paying attention to China's population, which would start declining in the 2020s, to be surpassed by that of India.
Women in high-fertility Niger queue for food (Photo by Feeding the Nations)
Life expectancy is expected to rise across all categories of countries, particularly as better treatment for HIV/AIDS cuts early deaths in many sub-Saharan African countries, Zlotnik said.
Global life expectancy is projected to increase from 68 years to 81 by the years 2095 to 2100.
While the world has not collapsed under the billions of new people, Zlotnik explained, most of the additions have taken place in the poorest countries.
High-fertility countries tend to be small, poor and racked by conflict, and Zlotnik said the UN is concerned that if they do not achieve their projected fertility reductions, they will have serious problems of food availability and affordability.
In April, the UN Food and Agriculture Organization's Food Price Index dropped for the first time after eight months of continuous price spikes.
The Index averaged 230 points in March 2011, down 2.9 percent from its peak in February, but still 37 percent above March of last year.
"The decrease in the overall index this month brings some welcome respite from the steady increases seen over the last eight months," said David Hallam, director of FAO's Trade and Market Division. "But it would be premature to conclude that this is a reversal of the upward trend."
"Low stock levels, the implications for oil prices of events in the Middle East and North Africa and the effects of the destruction in Japan," said Hallam, "all make for continuing uncertainty and price volatility over the coming months."