The world’s population will likely hit an estimated 8 billion people on Tuesday, according to a United Nations projection, with much of the growth coming from developing nations in Africa.

Among them is Nigeria, where resources are already stretched to the limit. More than 15 million people in Lagos compete for everything from electricity to light their homes to spots on crowded buses, often for two-hour commutes each way in this sprawling megacity. Some Nigerian children set off for school as early as 5 a.m.

And over the next three decades, the West African nation’s population is expected to soar even more: from 216 million this year to 375 million, the U.N. says. That will put Nigeria in a tie for third place with the United States after India and China.

The U.N.’s Day of 8 Billion milestone Tuesday is more symbolic than precise, officials are careful to note in a wide-ranging report released over the summer that makes some staggering projections.

The upward trend threatens to leave even more people in developing countries further behind, as governments struggle to provide enough classrooms and jobs for a rapidly growing number of youth, and food insecurity becomes an even more urgent problem.