Pope Francis is opening a divisive meeting on preserving the Amazon and ministering to its indigenous peoples, as he fends off attacks from conservatives who are opposed to his ecological agenda.

Francis was to celebrate an opening Mass on Sunday with global attention newly focused on the forest fires that are devouring the rainforest, which scientists say is a crucial bulwark against global warming. On hand are more than 180 cardinals, bishops and priests from the region who have gathered at the Vatican for three weeks of debate.

Among the most contentious proposals on the agenda is whether married elders could be ordained priests to address the chronic priest shortages in the region. Currently indigenous Catholics in remote parts of the Amazon can go months without seeing a priest or having a proper Mass.

Pope Francis looks on during a tree-planting ceremony on the occasion of the feast of St. Francis of Assisi, the patron saint of ecology, at the Vatican, Friday, Oct. 4, 2019. The ceremony takes place two days before a Synod of bishops on the Pan-Amazon region opens at the Vatican to address the ecological, social and spiritual needs of indigenous peoples in the Amazon. (AP PhotoAlessandra Tarantino)

Pope Francis looks on during a tree-planting ceremony on the occasion of the feast of St. Francis of Assisi, the patron saint of ecology, at the Vatican, Friday, Oct. 4, 2019. The ceremony takes place two days before a Synod of bishops on the Pan-Amazon region opens at the Vatican to address the ecological, social and spiritual needs of indigenous peoples in the Amazon. (AP PhotoAlessandra Tarantino)

Pope Francis is given a necklace by a member of an indigenous population on the occasion of the feast of St. Francis of Assisi, the patron saint of ecology, at the Vatican, Friday, Oct. 4, 2019. The ceremony takes place two days before a Synod of bishops on the Pan-Amazon region opens at the Vatican to address the ecological, social and spiritual needs of indigenous peoples in the Amazon. (AP PhotoAlessandra Tarantino)

Pope Francis is given a necklace by a member of an indigenous population on the occasion of the feast of St. Francis of Assisi, the patron saint of ecology, at the Vatican, Friday, Oct. 4, 2019. The ceremony takes place two days before a Synod of bishops on the Pan-Amazon region opens at the Vatican to address the ecological, social and spiritual needs of indigenous peoples in the Amazon. (AP PhotoAlessandra Tarantino)

Members of indigenous populations perform a tree-planting rite for Pope Francis on the occasion of the feast of St. Francis of Assisi, the patron saint of ecology, in the Vatican gardens, Friday, Oct. 4, 2019. The ceremony takes place two days before a Synod of bishops on the Pan-Amazon region opens at the Vatican to address the ecological, social and spiritual needs of indigenous peoples in the Amazon. (AP PhotoAlessandra Tarantino)

Members of indigenous populations perform a tree-planting rite for Pope Francis on the occasion of the feast of St. Francis of Assisi, the patron saint of ecology, in the Vatican gardens, Friday, Oct. 4, 2019. The ceremony takes place two days before a Synod of bishops on the Pan-Amazon region opens at the Vatican to address the ecological, social and spiritual needs of indigenous peoples in the Amazon. (AP PhotoAlessandra Tarantino)

Pope Francis meets members of indigenous populations on the occasion of the feast of St. Francis of Assisi, the patron saint of ecology, at the Vatican, Friday, Oct. 4, 2019. The ceremony takes place two days before a Synod of bishops on the Pan-Amazon region opens at the Vatican to address the ecological, social and spiritual needs of indigenous peoples in the Amazon. (AP PhotoAlessandra Tarantino)

Pope Francis meets members of indigenous populations on the occasion of the feast of St. Francis of Assisi, the patron saint of ecology, at the Vatican, Friday, Oct. 4, 2019. The ceremony takes place two days before a Synod of bishops on the Pan-Amazon region opens at the Vatican to address the ecological, social and spiritual needs of indigenous peoples in the Amazon. (AP PhotoAlessandra Tarantino)