Pope Francis declared Friday that there is a "right of the environment" and that mankind has no authority to abuse it, telling more than 100 world leaders and diplomats at the United Nations that urgent action is needed to halt the destruction of God's creation.
Hoping to spur concrete commitments at upcoming climate change negotiations in Paris, Francis accused the world's powerful countries of indulging a "selfish and boundless thirst" for money by ravaging the planet's natural resources and impoverishing the weak and disadvantaged in the process.
He asserted that the poor have inherent rights to education and what he has termed the "three L's" — lodging, labor and land.
Francis' speech, the fifth by a pope to the U.N., was a distillation of his recent teaching document on the environment, "Praise Be," which has delighted liberals and environmentalists and drawn scorn from big business interests.
By bringing the document to life before the U.N., Francis made clear his priorities.
"Any harm done to the environment, therefore, is harm done to humanity," he said.
Francis' speech kicked off what was expected to be a whirlwind day in New York that blended the powerful and the poor, from the solemnity of ground zero and to the struggles of East Harlem.
His visit was scheduled to include events as large as a processional drive through Central Park, as personal as meetings with schoolchildren and immigrants, and as inspiring for the faithful as Mass for thousands at Madison Square Garden.
Francis was greeted on his arrival at the U.N. by Secretary-General Ban Ki-moon, a key supporter of Francis' agenda.
In his opening remarks, Ban praised Francis for his priorities.
"You are at home not in palaces, but among the poor; not with the famous, but with the forgotten; not in official portraits, but in 'selfies' with young people," he said.
Among those in the audience for Francis' speech was Nobel peace laureate Malala Yousefzai, the young Pakistani education campaigner who was shot and gravely wounded by the Taliban. She will be addressing the U.N. summit later. Also on hand were German Chancellor Angela Merkel and Bill and Melinda Gates.
Before the speech, Francis signed a visitors' book then thanked U.N. staff in brief remarks he delivered in English.
"You are experts and experienced fieldworkers, officials and secretaries, translators and interpreters, cleaners and cooks, maintenance and security personnel," he said. "Thank you for all that you do."
Syed Mahmood Kazmi, of Pakistan, who works for the U.N., called Francis' speech memorable.
"He brings a message of love, peace and kindness for everyone," he said. "We need to move beyond religion and become global citizens for everyone. God has given him a billion followers."
Orla Murphy, 23 of Cork, Ireland, said that being at the U.N. as a youth delegate for the pope's visit was "overwhelming."
"It’s a dream to see the pope," she said. "To be honest, I think he’s giving a whole new lease on life to the Catholic Church."
Shea Spierings, 25, Australia's youth delegate from Brisbane, added that to her the pope "is about youth empowerment."
While Francis' visit marks the fifth time a pope has been to the United Nations, the Vatican flag was raised for the first time just before his arrival. The General Assembly recently agreed to allow the U.N.'s two observer states, the Holy See and Palestine, to fly their flags alongside those of the 193 member states.
Speaking in the packed General Assembly hall, Francis stated that "a right of the environment" exists.
He said the universe is the result of a "loving decision by the creator, who permits man respectfully to use creation for the good of his fellow men and for the glory of the creator: He is not authorized to abuse it, much less destroy it."
Echoing his encyclical's key message, he said a "selfish and boundless thirst for power and material prosperity leads both to the misuse of available natural resources and to the exclusion of the weak and disadvantaged."
He called for immediate access for the world's poor to adequate food, water and housing, as well as religious freedom.
He drew applause when he called for a reform of the U.N. system and international financial agencies to give poor countries a greater say.
That, he said, would ensure that they aren't subjected to "oppressive lending systems, which, far from promoting progress, subject people to mechanisms which generate greater poverty, exclusion and dependence."
While his speech carried a progressive social message, Francis also made clear that he firmly upholds the church's unchanging doctrine on life issues: He called for the "absolute respect for life in all its stages" — including the unborn. He cited "moral law written in nature itself" in insisting there is a natural difference between men and women. The Catholic Church has been on a campaign to denounce "gender theory" and the idea that people can choose their sex.
And he repeated his denunciation of the "ideological colonization" of the developing world — a reference to how Western, progressive ideas about contraception and gay rights are often imposed on poor nations as a condition for development aid.
After the U.N., the pope visited the 9/11 memorial, where two waterfall pools mark the outlines of the World Trade Center's twin towers before they were toppled by the terrorist attacks of Sept. 11, 2001.
He met relatives of some of the nearly 3,000 victims before heading below ground to the Sept. 11 museum for an interfaith service.
Francis' plans for Friday afternoon reflected the penchant of the "people's pope" for engaging with the public.
First on the agenda was a visit to Our Lady Queen of Angels School, set amid public housing in the heavily Hispanic neighborhood of East Harlem.
Known for ministering to the downtrodden in his native Buenos Aires, Francis was set to meet schoolchildren and offer a special blessing to refugees and immigrants, including people living in the country illegally.
Then he was to greet as many as 80,000 onlookers during a drive through Central Park, en route to Mass for 18,000 at Madison Square Garden.
Francis wraps up his U.S. visit this weekend in Philadelphia, where he speaks in front of Independence Hall and celebrates Mass on the Benjamin Franklin Parkway to close out a big rally on Catholic families.
—Sarah Glover contributed to this article