Nigeria: Fears over population growth as world hits 8 billion

More than 15 million people in Lagos are already competing for basic amenities of life.

Over the next three decades, the West African nation's population is expected to soar even more: From 216 million people this year to 375 million, the United Nations says, making Nigeria to the fourth most populous country in the world after only India, China and the United States.

Tuesday marks the UN projection for when the world's population is expected to hit 8 billion people, though officials are careful to note it's not a precise milestone.

Nigeria is among the eight countries that the UN says will account for more than half the world's population growth between now and 2050 - along with Congo, Ethiopia, and Tanzania, among others.

Other countries rounding out the list of those contributing most to the population increase are India, Pakistan, and the Philippines.

Such rapid population growth also means more people vying for increasingly scarce water resources and potentially more families facing hunger as climate change increasingly impacts crop production.

The UN has said that slowing population growth "over many decades could help to mitigate the further accumulation of environmental damage in the second half of the current century."

In sub-Saharan Africa, the population is growing at 2.5% - more than three times the global average.

Some of that can be attributed to people living longer, but family size remains the driving factor.

Women in sub-Saharan Africa on average have 4.6 births each, twice the current global average of 2.3.

Part of that can be traced to the high rate of child marriage, with 4 out of 10 girls married before they reach the age of 18, according to UN figures.

And the rate of teen pregnancy on the continent is the highest in the world, about half of the children born last year to mothers under 20 worldwide were in sub-Saharan Africa.

Omolayo Adeleke, a Nurse in Nigeria's busiest city believes that customs and traditions in some parts of the country play a major role in the high population figure.

Still, any efforts to reduce family sizes now would come too late to significantly slow the 2050 growth projections, the UN has said.

About two-thirds of it "will be driven by the momentum of past growth".

There are also important cultural reasons for large families that drive the tradition. In sub-Saharan Africa, children are seen as a blessing and as a source of support to their elders: The more sons and daughters, the greater success for the family and comfort in retirement.