All over the world, countries are confronting population stagnation and a fertility bust, a dizzying reversal unmatched in recorded history that will make first-birthday parties a rarer sight than funerals, and empty homes a common eyesore.

Maternity wards are already shutting down in Italy. Ghost cities are appearing in northeastern China. Universities in South Korea can’t find enough students, and in Germany, hundreds of thousands of properties have been razed, with the land turned into parks.

Like an avalanche, the demographic forces — pushing toward more deaths than births — seem to be expanding and accelerating. Though some countries continue to see their populations grow, especially in Africa, fertility rates are falling nearly everywhere else. Demographers now predict that by the latter half of the century or possibly earlier, the global population will enter a sustained decline for the first time.

A planet with fewer people could ease pressure on resources, slow the destructive impact of climate change and reduce household burdens for women. But the census announcements this month from China and the United States, which showed the slowest rates of population growth in decades for both countries, also point to hard-to-fathom adjustments.