Pope Francis has been preaching on marriage and family for a year, describing in increasingly vivid terms a global threat to what he has called "human ecology."

"We now live in a culture of the temporary, in which more and more people are simply giving up on marriage as a public commitment. This revolution in manners and morals has often flown the flag of freedom, but in fact it has brought spiritual and material devastation to countless human beings, especially the poorest and most vulnerable," he said last fall, at the Vatican's Humanum Conference on marriage.

"The crisis in the family has produced an ecological crisis, for social environments, like natural environments, need protection."

In his historic address to the U.S. Congress, the pope concluded with this same point: "I cannot hide my concern for the family, which is threatened, perhaps as never before, from within and without. Fundamental relationships are being called into question, as is the very basis of marriage and the family."

As a result, he warned, many young people are growing up "disoriented and aimless, trapped in a hopeless maze of violence, abuse and despair. … We might say that we live in a culture which pressures young people not to start a family, because they lack possibilities for the future. Yet this same culture presents others with so many options that they too are dissuaded from starting a family."

Ironically, while the world's attention was locked on Pope Francis during his U.S. visit, the event that brought him here -- The World Meeting of Families -- unfolded quietly in Philadelphia with 20,000 people in attendance, drawing little media attention.