New York City Mayor Bill de Blasio gestures as he holds a news conference during the “Modern Slavery and Climate Change” conference at the Vatican July 21, 2015. Photo courtesy REUTERS/Tony Gentile

VATICAN CITY (RNS) The mayors of New York, San Francisco and New Orleans were among the signatories to a Vatican declaration on Tuesday (July 21) pledging action on climate change and human trafficking.

The three were among more than 60 mayors invited to the Vatican to attend a two-day conference titled “Modern Slavery and Climate Change,” following on from Pope Francis’ environmental encyclical released last month.

The pledge specified bringing an end to “trafficking and all forms of modern slavery,” including prostitution and the selling of human organs.

READ: The ‘Splainer: Linking human trafficking, climate change and God

Among the 10 U.S. mayors to sign the declaration: New York Mayor Bill de Blasio, San Francisco Mayor Edwin Lee and New Orleans Mayor Mitchell Landrieu.

The mayors of Boulder, Colo.; Birmingham, Ala.; Portland, Ore.;  Minneapolis; San Jose, Calif.; Seattle; and Boston also signed the agreement, alongside a host of Latin American and European mayors. Paris Mayor Anne Hidalgo, who will host a key U.N. climate change summit in her city this December, was also a signer.

“As mayors we commit ourselves to building, in our cities and urban settlements, the resilience of the poor and those in vulnerable situations and reducing their exposure to climate-related extreme events and other economic, social and environmental shocks and disasters, which foster human trafficking and dangerous forced migration,” the resolution reads.

De Blasio addressed participants at the Vatican conference Tuesday, saying they had been invited to the Vatican to “upend” the status quo. “It’s now a matter of survival,” he said. “How do we justify holding back on any effort that may meaningfully improve the trajectory of climate change?”

The New York mayor used the Vatican platform to announce plans for his city to reduce carbon emissions by 40 percent by 2030, saying that local action was necessary to push national governments to take on the issue.

Landrieu agreed that it was up to local politicians to tackle the problems directly:

“(Pope Francis) has a very good political sense of how words are translated into action, because it really falls to the mayors to implement the policies that are enunciated by our national organizations.”

READ: Pope Francis’ approval ratings slump sharply in US, led by conservative dismay

Speaking to Vatican Radio, Landrieu also reflected on Hurricane Katrina, which devastated New Orleans in 2005. “As a result of climate change, more storms are coming,” he said. “They’re stronger; the impact is much more significant.”

The mayors’ meeting comes just two months before Francis embarks on a trip to the U.S., during which he will address Congress and is expected to touch upon climate change. His environmental message appears to have had a negative impact on his support basis in the U.S., however, where the pontiff’s popularity rating has slumped from 76 percent to 59 percent in a year.

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