The world population has now reached 8 billion

Eight billion. That’s the number of humans estimated to be alive on Earth.

On November 15, the global population reached this landmark, according to a projection from the United Nations.

In addition to being a cause for celebration, “the 8 billion milestone also brings important responsibilities, and highlights related challenges for social and economic development and environmental sustainability,” said Maria-Francesca Spatolisano, the U.N. assistant secretary-general for policy coordination and inter-agency affairs, at a news conference in July.

Though the global population continues to expand, the rate of growth is slowing. Current projections predict the world’s population will peak at about 10.4 billion in the 2080s and remain steady until 2100. Previously, the U.N. had predicted that the world’s population could reach 11.2 billion by 2100, based on the rate of population growth in 2017.

In the coming decades, migration is expected to be the sole driver of population growth in high-income countries, according to the World Population Prospects 2022 report, released by the U.N. in July. What’s more, the populations of 61 countries are projected to decrease by 1 percent or more between now and 2050. In lower-income countries, population growth is expected to still be driven by more births than deaths.

“There is inherent uncertainty in population projections,” said John Wilmoth, director of the U.N. Population Division, at the July news conference. This uncertainty, he said, is in part due to the possible range of trajectories of birth rates, mortality rates and emigration across various countries.

While rapid population growth in developing nations may intensify climate disasters, Spatolisano said, it’s important to keep in mind that “more developed countries — whose per capita consumption of material resources is generally the highest — bear the greatest responsibility for implementing strategies to decouple human activity from environmental degradation.”