Pope Francis appealed to conservatives on Sunday not to be bound by the status quo as he opened an assembly of bishops to discuss the future of the Roman Catholic Church in the Amazon, including the possibility of introducing married priests.

At a Mass in St. Peter’s Basilica opening the synod, Francis also denounced past and present forms of colonialism and said some of the fires that devastated forests in Brazil in recent months were set by special interest groups.

In his sermon, Francis said some Church leaders risked becoming “bureaucrats, not shepherds”, and urged them to have the courage of rekindling what he called the fire of God’s gift by being open to change.

“If everything continues as it was, if we spend our days content that ‘this is the way things have always been done’, then the gift vanishes, smothered by the ashes of fear and concern for defending the status quo,” he said.

One of the most contentious topics of the synod, whose some 260 participants are mostly bishops from the Amazon, is whether to allow older married “proven men” with families and a strong standing in local communities to be ordained as priests in the Amazon.

This solution to the shortage of priests, backed by many South American bishops, would allow Catholics in isolated areas to attend Mass and receive the sacraments regularly.

At least 85 per cent of villages in the Amazon, a vast region that spans eight countries and the French territory of Guiana — cannot celebrate Mass every week. Some see a priest only once a year.

Conservative opponents fear it would be a doctrinal Trojan horse that would then spread to the entire Church in the West.

They have attacked the synod’s working document as heretical, including what they say is an implicit recognition of forms of paganism and pantheism practised by indigenous people, such as nature worship.

The three-week synod will discuss spreading the faith in the vast region, a greater role for women, environmental protection, climate change, deforestation, indigenous people and their right to keep their land and traditions.

Bill Donohue, president of the US-based Catholic League, a conservative group, drew criticism for what was perceived as a condescending attitude toward native cultures when he said this week that a dilemma in the Amazon was “how to respect the culture of indigenous peoples while at the same time acknowledging inherent deficiencies in it.”

A number of conservatives have tweeted their disapproval of a tree-planting ceremony in the Vatican on Thursday in which people from the Amazon used native symbols and gestures, such as blessing the earth.

In his sermon, Francis said indigenous cultures had to be respected.

“When peoples and cultures are devoured without love and without respect, it is not God’s fire but that of the world. Yet how many times has God’s gift been imposed, not offered; how many times has there been colonisation rather than evangelisation!” he said.

The synod is taking place at a time when the Amazon is in the world spotlight because of the devastating fires in Brazil. Francis implied that he believed at least some of the fires were intentionally set.

“The fire set by interests that destroy, like the fire that recently devastated Amazonia, is not the fire of the Gospel (which is) fed by sharing, not by profits,” he said.

The synod does not make decisions. Participants vote on a final document and the Pope will decide which recommendations to integrate into his future rulings.