After a century in which the global population grew almost fourfold to 6.2 billion people, stoking fears of overpopulation, conflict, and ecological collapse, a turning point awaits. 

At some point in the 2060s, 2070s, or 2080s, the world population, currently 8 billion, will peak around 10 billion, according to forecasts, and then start to decline. An end to humanity’s relentless expansion is in sight. 

When it comes, debates about population growth, which have been driven by beliefs that humanity is too fecund for the Earth’s carrying capacity, will acquire a different character. What goes up fast can come down just as fast, measured in decades and centuries, setting the stage for an era of population shrinkage that seems both inexorable and unfathomable. 

Shrinkage is the logical result of tumbling birthrates today, not just in rich democracies like Germany and South Korea but also in most corners of the planet. “No future currently looks more likely than a long span of global depopulation,” says Dean Spears, an economist and demographer […]