VATICAN CITY — One hails from Tonga, where climate change threatens the existence of the archipelago. Several live in places tormented by drug violence and organized crime. Another represents a tiny, remote church that has witnessed firsthand the deadly drama of Mediterranean migration.

The 20 men from 18 countries who will join the College of Cardinals on Saturday reflect the far-flung diversity of the Catholic Church.

But they also represent unity in living out some of Pope Francis’ core concerns – and will bring that experience to bear when they eventually elect his successor.

Francis will formally elevate the new cardinals at a ceremony in St. Peter’s Basilica in the second such consistory of his pontificate. Like the first, Francis looked to the “peripheries” for new cardinals, giving countries that have never before had one – Tonga, Myanmar and Cape Verde – representation at the highest level of the Catholic Church.

Francis also looked to the peripheries in Italy, once again ignoring big archdioceses like Venice and Turin that have traditionally had a cardinal, to instead elevate prelates from small and often overlooked Italian dioceses.

Francesco Montenegro – the cardinal-designate from Agrigento, Sicily – welcomed Francis in July 2013, when the pope made his first trip outside of Rome to visit the tiny island of Lampedusa, a top destination for migrant smugglers since it’s closer to Africa than the Italian mainland.

There, Francis greeted several hundred recently arrived refugees and thanked the residents who have seen tens of thousands more arrive over the years and sometimes helped bring their bodies ashore when they died at sea.

In Lampedusa, Francis denounced the “globalization of indifference” that much of the world shows to refugees, a message he repeated this past week in decrying the deaths of some 300 migrants lost at sea.

Cardinal-elect Soane Patita Paini Mafi hails from Tonga, a tiny island state in the middle of the Pacific Ocean on the front lines in coping with the effects of global warming.

Tonga has never before had a cardinal, and Mafi’s concerns about climate change are much in line with those of the pope, who is writing an encyclical on the environment that has already irked climate change deniers in his own church.

“The pope has gone where no pope has ever gone before, which is to dioceses that are so far away from Rome and so small that they have never really showed up on the Vatican’s radar before,” said John Thavis, author of “The Vatican Diaries.”

“The peripheries have all these situations that are not exactly at the center of the (world’s) political and economic life,” Portuguese Cardinal-elect Manuel Jose Macario do Nascimento Clemente said Friday. “The pope wants (refugees and the poor) now to be at the center of the life of the church, also to be at the center of the life of the world.”

While cardinals are called on to advise the pope, their primary job is to elect a new one. Only those under age 80 can participate in a conclave. In addition to naming 15 voting-age cardinals, Francis also made five elderly churchmen cardinals to honor their service to the church.

One of them, Colombian Cardinal-elect José de Jesús Pimiento Rodriguez, wasn’t able to make the trip to Rome for the ceremony: He turns 96 next week.

Only one Vatican official, Cardinal-designate Dominique Mamberti, is getting a red hat, further evidence that Francis wants to reduce the number of titled Holy See bureaucrats.