But the outreach efforts to all corners of the Catholic world — a trademark of Francis’s tenure — have drawn criticism.
Some conservatives say the church is straying from its roots, acting more as a nongovernmental organization than a religion. Others have zeroed in on a proposal mentioned in the event’s working document: ordaining older married men to ease the severe shortage of priests in the Amazon basin.
Traditionalists warn that if the proposal is adopted at the end of the meeting, it could open the door for other parts of the world to challenge the Catholic tradition of an unmarried and celibate priesthood.
Even a notable Francis ally, Cardinal Marc Ouellet of Canada, expressed skepticism last week about the idea. “I think I’m not the only one,” he added.
This is the fourth time that Francis has convened the gathering of bishops, known as a synod. Such a meeting cannot set church policies or change doctrine on its own, but it offers guidance and recommendations to the pope and serves as a barometer for views around the Catholic world and within the church.
Cardinal Lorenzo Baldisseri, the synod’s secretary general, downplayed the relevance of the working document, telling reporters Thursday that participants will “start from scratch” once the event begins.
Still, that initial document conveys the pope’s thoughts, said Marco Politi, a veteran Vatican watcher and author of “The Loneliness of Francis.”
“It’s a watershed moment for his papacy,” Politi said. “Francis clearly has in mind a new model of church where lay people play a greater role. Either he scores a breakthrough, or he’s stopped in his tracks by conservative forces.”
Politi described the conservative backlash as similar to the Republican tea party movement against President Barack Obama. “They have become increasingly aggressive, so that it almost feels normal now that a bishop, or a cardinal, should call documents that have received the pope’s approval heretical,” he said.
In turning its attention to the Amazon, the Vatican is responding to several forces. Francis — the first pontiff from South America — has made environmental protection a major theme of his papacy. Additionally, the Catholic Church for decades has faced an erosion as the evangelical movement spreads across Brazil and other parts of Latin America.
In a recent essay, demographer José Eustáquio Diniz Alves wrote that the number of Catholics in Brazil may drop by 50 percent within the next three years and be surpassed by evangelicals before 2032.
“Francis never seeks interreligious clashes, but clearly the Brazilian bishops’ majority is colliding with some evangelical groups,” said Politi, who believes this to be “the most political synod of Francis’ papacy.”
Politi added that the event runs in opposition to the policies of Brazilian President Jair Bolsonaro, who came to power pledging to end or loosen environmental protections for the sake of economic growth.
“The pope believes natural and social decay are connected, so this synod acquires the very strong geopolitical meaning of a rift with other strong international leaders,” Politi said.
As if to show its dedication to the environment, the Vatican has recently made some small but symbolic changes.
In the Holy See press room, cups at the water cooler were recently changed from plastic to paper. The 185 participants coming to Rome from the Amazon and other parts of the world were only registered online, “to prevent paper waste,” Baldisseri said.
The Vatican considers the Amazon region to spread across nine countries. The biggest of those is Brazil, where some high-profile evangelical figures and others have voiced discomfort with the event.
Evangelical leader Estevam Hernandes, president of the March for Jesus — an event that has drawn Bolsonaro’s participation — said that the discussion will not help the region.
“We understand environmental concern, but it cannot hurt the sovereignty of our country,” he told The Washington Post.
Church traditionalists have tried to raise concerns of their own, holding events in Rome designed as counterprogramming to the synod.
“It’s a triple attack on marriage, celibacy and priesthood,” said José Antonio Ureta of the Plinio Correa de Oliveira Institute of Sao Paulo. If the requirement for priestly celibacy is loosened in the Amazon, he said, similar changes in “the rest of the church would be a matter of time.”
Marina Lopes in Sao Paulo, Brazil, contributed to this report.