A growing, more affluent population competing for ever scarcer resources could make for an "unrecognisable" world by 2050, warn researchers.
The United Nations has predicted the global population will reach seven billion this year, and climb to nine billion by 2050, "with almost all of the growth occurring in poor countries, particularly Africa and South Asia," says John Bongaarts of the non-profit Population Council.
To feed all those mouths, "we will need to produce as much food in the next 40 years as we have in the last 8000," says Jason Clay of the World Wildlife Fund at the annual meeting of the American Association for the Advancement of Science (AAAS).
"By 2050 we will not have a planet left that is recognisable" if current trends continue, says Clay.
John Casterline, director of the Initiative in Population Research at Ohio State University says the swelling population will exacerbate problems, such as resource depletion.
But incomes are also expected to rise over the next 40 years - tripling globally and quintupling in developing nations - and add more strain to global food supplies.
According to experts, people tend to move up the food chain as their incomes rise, consuming more meat than they might have when they made less money.
Previous research shows it takes around 7 kilograms of grain to produce a kilogram of meat, and around 4 kilograms of grain to produce a kilogram of cheese or eggs.
"More people, more money, more consumption, but the same planet," says Clay, urging scientists and governments to start making changes now to how food is produced.
Population experts, meanwhile, called for more funding for family planning programs to help control the growth in the number of humans, especially in developing nations.
"For 20 years, there's been very little investment in family planning, but there's a return of interest now, partly because of the environmental factors like global warming and food prices," says Bongaarts.
"We want to minimise population growth, and the only viable way to do that is through more effective family planning," says Casterline.