QUITO, Ecuador (AP) — Latin America's first pope returned to Spanish-speaking South America on Sunday for the first time Sunday, beginning an eight-day tour that will take him to three of the continent's poorest countries.

Outlining his message at a welcoming ceremony in Ecuador, Pope Francis stressed the need to protect the poor and the environment from exploitation and to foster dialogue among all sectors of society.

Children in traditional dress greeted Francis at Quito's Mariscal Sucre airport, the wind blowing off his skullcap and whipping his white cassock as he descended from the plane following a 13-hour flight from Rome. He personally greeted and kissed several indigenous youths waiting for him on the side of the red carpet.

In a speech in front of President Rafael Correa, Francis signaled some of the key themes for the visit, which will also take him to Bolivia and Paraguay: the need to care for society's most marginal, guarantee socially responsible economic development and defend the Earth against profit-at-all-cost development that he says harms the poorest the most.

"From the peak of Chimborazo to the Pacific coast, from the Amazon rainforest to the Galapagos Islands, may you never lose the ability to thank God for what he has done and is doing for you," he said. "May you never lose the ability to protect what is small and simple, to care for your children and your elderly who are the memory of your people, to have confidence in the young and to be constantly struck by the nobility of your people and the singular beauty of your country."

It's a message that will be keenly heard in Ecuador, a Pacific nation of 15 million people that is home to one of the world's most species-diverse ecosystems as well as the Galapagos Islands, which inspired Charles Darwin's theory of evolution. While oil has brought Ecuador unparalleled revenues in recent years, the accompanying deforestation and pollution have stained its vast swaths of rain forests where many indigenous peoples live.

Falling world prices for oil and minerals, though, is now threatening to fray the generous social safety net woven by Correa, who has been buffeted for nearly a month by the most serious anti-government street protests of his nearly nine years in power. Along Francis' motorcade route into Quito, some onlookers shouted "Correa out!" and gave a thumbs' down gesture.

Standing by Correa's side at the airport, Francis pledged that the Catholic Church was ready to help meet the challenges of the day by encouraging a respect for peoples' differences, "fostering dialogue and full participation so that the growth in progress and development already registered will ensure a better future for everyone, with particular concern for the most vulnerable of our brothers and sisters."

Thousands lined the route that took Francis to the Vatican ambassador's residence, many hopeful the pope would have a calming effect on the country's tense political situation.

Travel agency worker Veronica Valdeon called the Argentine pontiff "a light in the darkness."

"We are living difficult moments in our country, and Francis brings a bit of joy," Valdeon said.

The "slum pope" chose to visit Ecuador, Bolivia and Paraguay specifically because they are among the poorest and most marginal nations of a region that claims 40 percent of the world's Catholics. He's skipping his homeland of Argentina, where he ministered to the poorest slum-dwellers while archbishop, to avoid papal entanglement in this year's presidential election.

The schedule for Monday is relatively easy, to help the 78-year-old pontiff get acclimated. He will fly an hour south to Ecuador's steaming Pacific port city of Guayaquil, where more than 1 million people are expected to attend his first public Mass. Before returning to Quito, he'll have lunch with two dozen Jesuits at a Jesuit school where he used to send his own Argentine seminarians to study.

Francis' stops later include a violent Bolivian prison, a flood-prone Paraguayan shantytown and a meeting with grass-roots groups in Bolivia, the sort of people he ministered to in the slums of Buenos Aires.

Crowds are expected to be huge. While the countries themselves are small, they are fervently Catholic: 79 percent of the population is Catholic in Ecuador, 77 percent in Bolivia and 89 percent in Paraguay, according to the Pew Research Center.

Beyond the major public Masses in each country, Vatican organizers have scheduled plenty of time for the pope to meander through the throngs expected to line his motorcade route.

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Associated Press writers Gonzalo Solano and Maria Jose Sanchez contributed to this report.