The original version of this article, by Carl Haub, appeared on
Yale Environment 360.
In a mere half-century, the number of people on the planet has soared from 3 billion to 7 billion, placing us squarely in the midst of the most rapid expansion of world population in our 50,000-year history – and placing ever-growing pressure on the Earth and its resources.
But that is the past. What of the future? Leading demographers, including those at the United Nations and the U.S. Census Bureau, are projecting that world population will peak at 9.5 billion to 10 billion later this century and then gradually decline as poorer countries develop. But what if those projections are too optimistic? What if population continues to soar, as it has in recent decades, and the world becomes home to 12 billion or even 16 billion people by 2100, as a high-end UN estimate has projected? Such an outcome would clearly have enormous social and environmental implications, including placing enormous stress on the world’s food and water resources, spurring further loss of wild lands and biodiversity, and hastening the degradation of the natural systems that support life on Earth.
It is customary in the popular media and in many journal articles to cite a projected population figure as if it were a given, a figure so certain that it could virtually be used for long-range planning purposes. But we must carefully examine the assumptions behind such projections. And forecasts that population is going to level off or decline this century have been based on the assumption that the developing world will necessarily follow the path of the industrialized world. That is far from a sure bet.
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Image Credit: Data from UN Population Division, chart arranged by Schuyler Null.