The recent comment by Pope Francis that people who have pets instead of children are, sometimes at least, manifesting selfishness brought predictable howls from pet lovers and those who felt he was treading on their sacred right to do whatever they please. But along with unintentionally giving media the sort of juicy flap over trivia that they relish, the pope was identifying a grave and growing problem for nations around the globe.

The problem isn't pets. It's declining population in places where births have fallen below the replacement rate -- 2.1 children per woman -- required to hold population at a steady level.

On a list of 200 countries, 104 are at or above the replacement rate and the rest below. Here are a few of the places that are in trouble, together with their fertility rates: France -- 1.870, China -- 1.696, United Kingdom -- 1.650, Germany -- 1.540, Russia -- 1.504, Japan -- 1.360, Italy -- 1.270. And for the United States, the figure was a dismal 1.705, placing it 144th on the list, right after the Czech Republic (1.710) and just before Ireland (1.700).

These numbers are World Bank figures for 2019, but indications are that the declines are continuing. Last year, for instance, the U.S. birthrate fell for the sixth year in a row, while, in mid-January, China said births there had dropped an eye-popping 1.4 million in 2021, to 10.6 million from 12 million the year before.

Remember the "population bomb" scare of the 1960s and 1970s, when population controllers warned that the number of people in the world would soon exceed the world's ability to support them? What's happening now is an implosion -- societies collapsing in on themselves -- and that's genuine bad news.

The consequences for places where population is falling will, to say the least, not be pleasant. The most obvious scenario is fewer working-age people to support what is likely to be a growing number of no longer working elderly persons. And that in turn will breed new intergenerational tensions, no doubt accompanied by fresh pressure for legalized euthanasia as a tool of enlightened social policy.

Yet it needn't be that way. According to Nicholas Eberstadt of the American Enterprise Institute, a knowledgeable student of demographic trends, prosperity remains a possibility in the face of falling population. But although it's possible, he added in National Review, it is "by no means certain." The reason being that "dynamism in our economy and society is on the wane" as reflected in areas ranging from new business enterprises and population mobility to life expectancy, educational attainment, and immigration policy.

And now marriages and births.

Says Eberstadt: "Pessimism, hesitance, dependence, self-indulgence, resentment, and division: Do we really think there will be less of these in a 1.5-child America?"

Leaving aside the pope's bit about pets and selfishness, which reflected his familiar fondness for off-the-cuff zingers, more to the point was his observation that people without children "are lacking something, something fundamental."

So what do they lack? Children of course. But also something else. Opting for a child is a way of saying that, despite all its problems, life is a good thing and the future bright enough to want to share it with someone else.

As I was writing this, I came across a statement by New Jersey bishops expressing disappointment at enactment of a highly permissive new abortion law in their state. "We have failed as a society when a response to any pregnancy is fear rather than joy," they said. Now there's something worth worrying about.

- Russell Shaw is the author of more than twenty books. He is a consultor of the Pontifical Council for Social Communications and served as communications director for the U.S. Bishops.