Pope Francis on Tuesday appealed to the world not to turn its back on the "reality" of environmental decay and its effects on the poor, saying protecting the planet was no longer a choice but a duty.
The pope, in a speech to university professors and students on the third day of his trip to Ecuador, made his first full-court press on environmental issues since the publication last month of his ecology encyclical "Laudato Si."
Francis has said he wants the encyclical to influence a United Nations climate change summit in Paris in December and has now effectively taken his campaign to convince governments on the road. In September, he visits the United States and the United Nations.
"One thing is certain: we can no longer turn our backs on reality, on our brothers and sisters, on Mother Earth," he said at the Pontifical Catholic University of Ecuador.
While he did not specifically mention climate change or its causes, he quoted often from the encyclical, which said there was a "very solid scientific consensus" on global warming and its human causes.
He appeared to be making a clear reference to climate change doubters when he said: "It is wrong to turn aside from what is happening all around us, as if certain situations did not exist or have nothing to do with our lives."
In the encyclical Francis demanded swift action to save the planet from environmental ruin, called for policies to "drastically" reduce polluting gases and gradually cut dependence on fossil fuels.
In Tuesday's speech, the pope said: "We are also invited to care for it, to protect it, to be its guardians. Nowadays we are increasingly aware of how important this is. It is no longer a mere recommendation, but rather a requirement ..."
His choice of Ecuador to make his first post-encyclical speech on the environment was not casual.
Ecuador is heavily reliant on oil and mining while boasting some of the world's greatest biodiversity including the Galapagos Islands, on which Charles Darwin formulated his ideas on evolution.
The leftist government of President Rafael Correa, which introduced austerity measures after a major drop in oil prices, is walking a tightrope between business and protecting the environment.
WARM-UP FOR U.S. VISIT
The pope's words in Ecuador were a foretaste of his September trip to the United States, where most criticism of the encyclical has come. Conservatives, including several Republicans seeking their party's nomination to run for president in 2016, have said the pope should not meddle in scientific affairs.
But he has won wide backing from advocates of environmental protection, including U.S. President Barack Obama and U.N. Secretary General Ban Ki-moon.
In his comments at the university, the pope who has made defense of the poor a key plank of his papacy also touched on the politically delicate issue of whether nature could be considered private property.
"It is a gift, a present, an offering. It is not something that can be bought or acquired. It precedes us and it will be there long after us," said the Argentine pontiff, whose Latin America "homecoming" is to three of the region's poorest countries - Ecuador, Bolivia and Paraguay.
Francis started his last full day in Ecuador by saying an open-air Mass for nearly a million people on the grounds of a former airport in the capital, Quito.
In his homily, he called on people across Latin America to turn to their common Christian roots as an inspiration to resolve differences.
Tens of thousands of people braved wind and rain to camp out overnight. The weather later changed and the service took place under a hot sun.
Isabel Pavon, 55, came with her two small children, a boy and a girl who held up small wooden crosses.
"It is such a joy to be here," she said, pressed up against a security fence. "He is our pope, the pope of the people."
His visit on Wednesday to the high altitude Bolivian capital, La Paz, will focus attention on the 78-year-old pope's health as he had part of one lung removed when he was younger after an infection that almost took his life.
