World population to reach 10.1 billion by 2100

The projections are used by the United Nations and its many agencies to devise and fund programs for problems ranging from climate change to maternal mortality.

The U.N. said in a report on world trends released Tuesday that global population is expected to officially hit 6.9 billion on July 1 and 7 billion on Oct. 31. Most of the increase is expected from the world's "high-fertility countries," especially in sub-Saharan Africa.

U.N. Population Division Director Hania Zlotnik said the projections depend on expected fertility rates, with populations in many nations aging as medical advances allow people to live longer and families opt to have fewer children.

"The world hasn't collapsed by adding so many people, but most of the people have been added in the poorest countries," Zlotnik noted. "If they don't achieve the lower level of fertility we are projecting they could have serious problems."