India marked the arrival of girl named Nargis Monday as the world's symbolic seven billionth citizen, the Plan India child rights group said.
"Seven billion will clearly be a serious challenge," Ban had told Time magazine. "But depending on how we address this, in a comprehensive manner it can be both an opportunity and challenge.
Ban said he suspected the 7 billionth citizen would face "a world of contradiction -- plenty of food, but still a billion people going to bed hungry every night. Many people enjoy luxurious lifestyles, but still many people are impoverished."
Ban said the milestone was "clearly a clarion call to action," not just for the United Nations and national governments, but also for "local communities, civil community leaders, non-governmental organizations, faith leaders -- we have to have a combined solidarity to address this issue."
Ban planned to hold a news conference Monday to mark the 7 billionth birth -- out of an estimated 382,000 births during the day. He also planned to talk about challenges ahead, including poverty and sustainable development, his office said.
Food production, for instance, will need to jump 70 percent in two generations to feed the planet by 2050, the United Nations' Food and Agriculture Organization says.
With more than two babies born every second, the global population is forecast to hit 8 billion in about 14 years and 10 billion by the end of the century, says the U.N. Population Division, part of the U.N. Department of Economic and Social Affairs. The global population was 6 billion in 1999.
The world population was 1.6 billion in 1900, a total that took an estimated 50,000 years to reach, Washington's private Population Reference Bureau says.
Ban also planned to take his message to the Group of 20 summit in in Cannes, France, Thursday and Friday, his office said.
Monday's date is symbolic, the U.N. Population Division says, acknowledging it is impossible to know for sure the specific time or day when the 7 billionth person is born.
The U.S. Census Bureau estimates the 7 billion threshold will be reached next March. The private Population Reference Bureau, also based in Washington, says the 7 billion figure was passed several weeks ago.
Officials in India predicted the baby bringing the population to 7 billion would be born Monday in India's most populous state, Uttar Pradesh, with an estimated 200 million people.
Nearly all the projected growth this century is expected to occur in developing countries in Asia, Africa and Latin America, while the populations in Europe, North America and other industrialized nations will remain relatively flat, the U.N. Population Division says.