The world population growth from 7 to 8 billion, which took 12 years, is the fastest in the world's recorded history.

Meanwhile, India is expected to replace China as the most populous country in the world by 2030. But on a brighter note, the report also indicated that it will take approximately 15 years, until 2037, for the world population to reach 9 billion — a sign that the overall growth rate of the global population is slowing!

Meanwhile, a new report from the United Nations has stated that the world population is set to touch 8 billion by November 15! According to the UN report, this unprecedented growth can be attributed to the gradual increase in human lifespan thanks to improvements in public health, nutrition, personal hygiene and medicine. It is also the result of high and persistent levels of fertility in some countries.

What's concerning is that countries with the highest fertility levels are almost always those with the lowest income per capita. Global population growth has hence become increasingly concentrated among the world's poorest countries, most of them in sub-Saharan Africa.

Nigeria, for instance, is one among the eight countries that the UN says will account for more than half the world's population growth between now and 2050. With resources already stretched to the limit, over 15 million people in Lagos compete for every basic necessity, from electricity to light their homes to spots on crowded buses.

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 UN says. That will make Nigeria the fourth-most populous country in the world after India, China and the United States.

The UN's Day of 8 Billion milestone on Tuesday is more symbolic than precise. Even though population growth magnifies the environmental impact of economic development, rising per capita incomes are the primary driver of unsustainable production and consumption patterns.