By Philip Pullella and Girish Gupta

QUITO (Reuters) - Pope Francis on Tuesday said protecting the planet was no longer a choice but a duty and called for a new "social justice" where access to the earth's resources would be based on equality instead of economic interests.

In back-to-back speeches on the third day of his trip to Ecuador, the pope made his first full-court press on environmental issues since the publication last month of his landmark ecology encyclical "Laudato Si.".

Speaking before a group that included indigenous people of the Equatorial Amazon, he also renewed his call for special protection for the area because of its vital importance to the planet's ecosystem.

The pope has said he wanted 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 takes his message to 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 in a first speech 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.

"We are also invited to care for it (the planet), 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 speeches 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.

'SOCIAL MORTGAGE'

In both speeches the first pope from Latin America, 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.

"The goods of the earth are meant for everyone, and however much someone may parade his property, it has a social

mortgage," the Argentine pontiff told a group of civic leaders in Quito's St. Francis Church, the oldest religious building in Latin America.

"In this way we move beyond purely economic justice, based on commerce, towards social justice, which upholds the fundamental human right to a dignified life," he said in the church, whose construction began in 1536.

"The tapping of natural resources, which are so abundant in Ecuador, must not be concerned with short-term benefits. As stewards of these riches which we have received, we have an obligation toward society as a whole and towards future

generations," he said.

His words in Ecuador were a foretaste of his September trip to the United States, where most of the 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.

At the second meeting on Tuesday, representatives of two Amazon indigenous people, the Tagaeri and the Taromenane, were due to give him a letter saying they were living "in the shadow of extermination".

In that speech, the pope quoted from his encyclical, saying the Amazon "requires greater protection because of its immense importance for the global ecosystem … it possesses an

enormously complex biodiversity which is almost impossible to appreciate fully."

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 Ecuadorean capital, Quito. He visits Bolivia on Wednesday and the last leg of the trip is Paraguay.

(Additional reporting by Alexandra Valencia; Editing by Mary Milliken and Grant McCool)