ROME — Indigenous leaders of the Amazon offered up prayers for the Earth in the Vatican gardens on Friday with Pope Francis, who consecrated the upcoming Pan-Amazon Synod to St. Francis of Assisi.

During the prayer ceremony, Pope Francis planted a tree from Assisi in the gardens as a symbol of “an integral ecology” — to consecrate the Amazon Synod to St. Francis — in the imminent 40th anniversary of the papal proclamation of St. Francis as the patron saint of environmentalists.

“We place the Synod under the protection of St. Francis,” the pope said in his remarks. “His life and work give us the essential lines to discern new paths for the Church and for an integral ecology.”

“Let us ask the ‘Poverello’ of Assisi to intercede for this synod, so that we may live a process of ecological and pastoral conversion and allow ourselves to be seriously challenged by the geographical and existential peripheries of the Amazon,” he said.

Representatives of the indigenous peoples of the Amazon took part in the ceremony, dancing, singing, and offering prayers for the Earth, accompanied by their traditional instruments.

The pan-Amazon synod, which has a strong ecological thrust, opens in the Vatican on Sunday and will last until October 27.

A number of prominent prelates have criticized the working document of the upcoming synod of bishops, saying the text contains elements that undermine the Catholic faith.

In letters dated August 28, Cardinals Raymond Burke and Walter Brandmüller warned fellow cardinals that the synod poses serious challenges to perennial Church teaching.

“Some points of the synod’s Instrumentum laboris (working document) seem not only in dissonance with respect to the authentic teaching of the Church, but even contrary to it,” Cardinal Walter Brandmüller said in his letter.

For his part, Cardinal Burke said that the “disturbing propositions of the Instrumentum laboris portend an apostasy from the Catholic faith.”

In mid-July, Cardinal Gerhard Müller, the former prefect of the Vatican’s Congregation for the Doctrine of the Faith, issued a lengthy critique of the synod’s working document, lamenting its “upside-down hermeneutics” and appeals to a “cosmovision with its myths and the ritual magic of Mother ‘Nature.’”

Pope Francis has said that the Vatican synod will focus heavily on environmental issues, declaring that climate change is a “global emergency” and insisting that what he fears most is a loss of biodiversity.

The pope said that the synod is a “child” of his 2015 encyclical Laudato Si on care for creation.

“Those who have not read it will never understand the Synod on the Amazon. Laudato Sì is not a green encyclical; it is a social encyclical, which is based on a ‘green’ reality, the custody of Creation,” he said.

The Amazon, Francis said, is a “representative and decisive place,” which explains why it was chosen for this year’s synod.

“Together with the oceans, it contributes decisively to the survival of the planet,” he said. “Much of the oxygen we breathe comes from there. That is why deforestation means killing humanity.”

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