On Nov. 15, the United Nations estimated that the global population had reached 8 billion people. Marie-Francesca Spatolisano, the U.N. assistant secretary-general for Policy Coordination and Inter-Agency Affairs, said at a news conference in July, “the 8 billion milestone also brings important responsibilities and highlights related challenges for social and economic development and environmental sustainability.”

The U.N. reported that the increase in population has contributed to environmental challenges, including climate change, deforestation and the loss of biodiversity. Humanity’s achievements in medicine, nutrition, public health and hygiene have contributed to population growth.

The United Nations forecasts that the world population will reach 9 billion in 2037 and 10 billion in 2058. People are living longer and fertility rates have surged in some countries.

The population growth is uneven. Two-thirds of all people live in regions where the fertility rate, measured in births per woman, has fallen below the replacement rate of 2.1. Population growth has decelerated because of a number of factors, including more readily available birth control and better education.

Originally published in the Sarasota Herald-Tribune