Pope Francis has challenged Latin America's youth to take up his environmental protection campaign, saying the defence of God's creation is not just a recommendation but a requirement.

Pope Francis' appeal, delivered at Quito's Catholic University, is particularly relevant for Ecuador, a Pacific nation that is home to one of the world's most species-diverse ecosystems in the Galapagos Islands and Amazon rainforest, but is also an Opec country heavily dependent on oil extraction.

The pontiff told students and professors that God gave humanity the Earth to not only cultivate, but to care for - a message he framed earlier this month in his headline-grabbing encyclical on the environment.

"It is no longer a mere recommendation, but rather a requirement because of the harm we have inflicted on it by our irresponsible use and abuse of the goods with which God has endowed it," he said.

He challenged universities to ensure that students' educations are not aimed only at profitable careers but also at helping the poor and the environment.

"There is a relationship between our life and that of mother Earth, between the way we live and the gift we have received from God," he said.

Pope Francis' environmental message has been cheered by indigenous groups, who have complained of being increasingly marginalised by Ecuadorean president Rafael Correa as he pushes mining and oil drilling in the Amazon.

That push, coupled with high crude prices, allowed Mr Correa to lift 1.3 million people out of poverty in his eight years in office.

Pope Francis has called for environmentally-responsible development, one that is aimed at helping the poor without sacrificing the planet.

It was a message he was likely to repeat later in the day at a meeting with indigenous groups, and then later this week in Bolivia, the next stop on his three-nation South American tour.

Bolivian president Evo Morales has been hailed as an environmental hero to many for demanding rich nations do more to halt global warming, but he has been assailed by conservationists at home who say he puts oil and gas extraction ahead of clean water and forests.

Pope Francis began his last full day in Ecuador with an open-air Mass that drew more than one million people and featured readings in Quichua, the native language mostly spoken in Ecuador, and Ecuadorean vestments for the pope.

In his homily, Pope Francis urged Latin Americans to channel the same urgency that brought them independence from Spain two centuries ago into spreading the faith on a continent where Catholicism is losing souls to evangelical movements.

The Mass location, at Quito's Bicentennial Park, was appropriate given that Ecuador was where the first cries of independence against Spanish rule arose in Latin America in 1809.

"There was no shortage of conviction or strength in that cry for freedom which arose a little more than 200 years ago," Pope Francis said. "But history tells us that it only made headway once personal differences were set aside."

He urged Latin Americans to channel that same purpose and unity into spreading the faith. Latin America counts 40 per cent of the world's Catholics, but the church is losing out to protestant evangelical ministries that have focused on the continent's poorest communities with real-life guidance on employment and education.

While the drop-off in Spanish-speaking South America has not been as sharp as it has been in Brazil, it is notable. Some 95 per cent of Ecuador's population was Catholic in 1970, and now the figure is down to 79 per cent, according to the Pew Research Centre.

In a bid to counter the trend and return the Catholic Church to its evangelising origins, Pope Francis has called for the church to return to being a missionary church that looks out particularly for society's poorest and most marginalised. It is a message he crafted for the entire Latin American church when he played a leading role in a 2007 conference of bishops in Aparecida, Brazil.

"Evangelisation doesn't consist in proselytising, but in attracting by our witness to those who are far off, in humbly drawing near to those who feel distant from God and the church, those who are fearful or indifferent," Pope Francis told the crowd. "Proselytism is a caricature of evangelisation."

Pope Francis arrived at Bicentennial Park to cheers of people who camped out overnight for a good spot. They were rewarded with a pre-dawn deluge that sent some 20 people to paramedics with hypothermia, said city operations director Cristian Rivera. But the sun broke out as Francis arrived in his popemobile, with fans tossing confetti on him as he zoomed by.

"The joy at seeing the pope gives us the warmth we need," said Abel Gualoto, a 59-year-old seafood vendor as he rubbed his cold hands together to try to stay warm.