“We are concerned about the vast fires that have developed in the Amazon,” the pope told the faithful at the Vatican.
“That forest lung is vital for our planet.”
He urged the world’s 1.3 billion Catholics to pray for the fires to be extinguished as quickly as possible.
Official figures show 78,383 forest fires have been recorded in Brazil this year, the highest number of any year since 2013.
The Argentine pope, who will gather bishops for a conference on the Amazon in October, met Brazilian indigenous leader Raoni in 2013 when he toured Europe warning of the dangers of deforestation.
The pope denounced the exploitation of the Amazon by “huge international economic interests” in a 2015 encyclical.
In January 2018 he visited Puerto Maldonado village in the Amazonian jungle of southeastern Peru where thousands of tribespeople had gathered, including from neighbouring Brazil and Bolivia.
The Catholic Church acknowledges the bloody history of the spread of Christianity through South America and that it has not always respected Amazon tribes. Today it is committed to numerous projects to support indigenous populations.