HUMANITY is continuing to grow and the Earth's population could hit 12 billion by 2100, according to a new prediction by experts.
The rising population could worsen world problems such as climate change, infectious disease and poverty, scientists warn.
Previous estimates have suggested that after peaking at around nine billion by the end of the century the global population would level off or even decline.
US statistician Professor Adrian Raftery, from the University of Washington, said: "We found there's a 70% 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."
Currently, the size of the Earth's population is 7.2 billion.
The team used advanced statistical techniques to analyse latest United Nations data and estimate future demographic trends affecting fertility, life-expectancy and migration.
The projection shows an 80% likelihood that the global population will increased to between 9.6 and 12.3 billion by 2100.
Most of the growth is expected to take place in Africa, where the population is expected to quadruple from around one billion today to four billion by the end of the century.
In sub-Saharan Africa, fertility levels remain high and large families - typically with more than four children - are still common, the researchers point out.
Reductions in the death toll from HIV/Aids are said to be another contributing factor to the African trend.
Other parts of the world will see less change, according to the research published in the journal Science. Asia's population, now at 4.4 billion, is predicted to peak at around five billion in 2050 and then begin to decline.
North American, European, Latin American, and Caribbean populations are likely to stay below one billion in each region.
Prof Raftery added: "This paper brings together the research from the past seven years, and also brings in recent data. 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 kept in check by more investment in education and family planning programmes that provide contraceptives, said the researchers.