Among the major challenges will be reversing the decline in the number of priests worldwide.
CHRISTIAN SCIENCE MONITOR
The Roman Catholic cardinals who file into the Sistine Chapel today for the first conclave in a quarter century have a difficult task. They must elect a man who can not only fill the shoes of an immensely popular pope, but lead a global church with urgent and complex challenges.
The dynamic era of John Paul II spurred major growth in the church and gave the papacy added clout on moral issues. But it also left unfinished business that will seriously test the next pontiff.
Among the bigger challenges:
UReplenishing a global shortage of priests. Last year, 17 percent of parishes in North America had no priest.
USettling the balance of power between bishops and the pope. John Paul II recentralized power in Rome, but many Catholics urge local control.
UMaking the church's teaching on sexuality and family more relevant to lay Catholics.
UDealing with challenges from Islam and evangelical traditions, while improving interfaith ties.
The next pope will assume the mantle at a time of heightened insecurities in the world. Religious competition and conflict in several regions demand his attention, along with the persistent challenges of globalization and poverty.
For an institution centered on the Eucharist and defined by a sharp distinction between clergy and laypeople, the shortage of priests is potentially devastating. "The Catholic Church wouldn't be Catholic without the Eucharist and sacraments, and it can't have them without priests," says the Rev. Thomas Reese, editor of America, a Catholic weekly.
Despite John Paul II's travels and inspiring persona, the number of priests worldwide remains the same as at the start of his pontificate, while the Catholic population has grown by 40 percent.
In North America, there is one priest for every 1,300 parishioners. In South America, the ratio is one for every 7,000. The fact that priests in many places on that continent show up only once a month to say mass has helped spur the exodus to evangelicalism, researchers say.
Clergy and laypeople want the new pope to consider the possibility of married priests. "The next pope must acknowledge that providing the ... sacraments ... is more important than mandatory celibacy," the Rev. Mr. Reese argues.
Perhaps the most difficult test facing the new pontiff will be how to devolve authority within the institution, an issue rankling church leaders around the world. John Paul put power back in the Vatican, clipping the wings of bishops conferences and local churches, stifling debate, and making it more difficult to adapt practices to local cultural contexts.
"Problems differ in various parts of the world, and people want less intrusion from Rome in their affairs," says Paul Lakeland, professor of religion at Fairfield University in Connecticut. "People on the right and on the left both want that."
The balance of power between the Vatican and bishops -- what in the church is called "collegiality" -- is seen as a prime issue for cardinals in this week's voting.
Some Catholics say it's time to consider electing bishops at the local level, a practice that occurred in earlier periods in the church. Others suggest that devolution should include more responsible involvement of the laity.
In today's atmosphere of global tensions, the new pope will have to decide how best to build on his predecessor's monumental efforts in interfaith relations. By most accounts, Islam tops the agenda. Catholic communities face difficult encounters with Islam in Africa and elsewhere, and it's crucial for the church to reach some kind of modus vivendi.
John Paul met more than 50 times with Muslim leaders, and won appreciation in the Muslim world by showing respect for the faith. He apologized for past errors, visited a mosque, and when a Koran was given to him, he kissed it. And unlike some Protestant preachers, he stated that Christians and Muslims pray to one God.
"He saw his dialogue as work of peace-building," says Diana Eck of Harvard University, who participated in interfaith discussions with the Vatican.
Some critics in and outside the Vatican now argue for a tougher line, and acknowledgment of the religious rivalry with Islam. They say it's time for Muslim leaders to provide some guarantees on religious freedom for Christians.