The world's population is projected to reach 8 billion on November 15, the United Nations (UN) reminded the international community on November 15.

It is "a milestone in human development," said the UN press release. "This unprecedented growth is due to the gradual increase in human lifespan owing to improvements in public health, nutrition, personal hygiene and medicine."

While it took the global population 12 years to grow from 7 to 8 billion, it will take approximately 15 years, until 2037, for it to reach 9 billion, a sign that the overall growth rate of the global population is slowing, said the release.

"The milestone is an occasion to celebrate diversity and advancements while considering humanity's shared responsibility for the planet," said UN Secretary-General Antonio Guterres.

"It is also the result of high and persistent levels of fertility in some countries," added the report.

Countries with the highest fertility levels tend to be those with the lowest income per capita. Global population growth has therefore over time become increasingly concentrated among the world's poorest countries, most of which are in sub-Saharan Africa, read the release.

Even though population growth magnifies the environmental impact of economic development, rising per capita incomes are the main driver of unsustainable patterns of production and consumption, added the release.

"Yet, slower population growth over many decades could help to mitigate the further accumulation of environmental damage in the second half of the current century," said the release.