In a show of solidarity with Pope Francis’ recently expressed concerns about the environment, an estimated 5,000 people took to the streets of Rome Sunday calling on world leaders to take immediate action on the issue, according to the Guardian in the U.K. The rally was conducted ahead of a meeting between Vatican officials and environmental-preservation leaders this week and a major climate-change conference in Paris in December.

The pontiff laid the moral groundwork for how the Roman Catholic Church should address environmental concerns in the “Laudato Si” encyclical letter he had published this month. He also cited scientific research centered on global warming and other environmental issues, according to a leaked version of the 192-page letter appearing in the Italian magazine L’Espresso.

“Humanity is called to take note of the need for changes in lifestyle and changes in methods of production and consumption to combat this warming, or at least the human causes that produce and accentuate it,” the Guardian quoted the pope as writing. “Numerous scientific studies indicate that the greater part of the global warming in recent decades is due to the great concentration of greenhouse gases ... given off above all because of human activity.”

We know how unsustainable is the behaviour of those who constantly consume and destroy. — Pope Francis (@Pontifex) June 19, 2015

Many things have to change course, but it is we human beings above all who need to change. — Pope Francis (@Pontifex) June 19, 2015

Activists in the environmental space have lauded Francis’ words, which have been seen as a departure from previous commentaries by the typically conservative church. They expressed the hope that these words may cause world leaders to pay attention to their issue.

“The reason we are here is to thank Pope Francis, but above all it is to bring a message to the people and politicians on the Paris climate-change conference – to make strong, ambitious and binding commitments,” said Andrea Stocchiero, a member of the group Focsiv that co-organized the rally in Rome Sunday, according to the Guardian.

In support of the pope’s position on the environment, other religious leaders were represented at the rally, sending the message of “many faiths, one planet.”

Kiran Bali traveled to Italy from the U.K. to be there as a member of the Hindu community. “It’s so clear that the world is at a crucial tipping point due to climate change, and it’s so important that faith leaders take action on this important issue,” she told the Guardian. “Now is the time to unite, to come together and to really make a difference to protect the earth from further destruction.”

“The challenge facing Europe and all of the industrialized and industrializing world is very important -- we’re going to choke or cook unless we do something about it,” David Moxon, a representative of the Anglican community, told the newspaper.

Of course, the pontiff’s lengthy letter encompassing the climate-change issue was not universally welcomed.

A couple of Catholics who are running for the Republican Party’s nomination in the 2016 U.S. presidential race made a point of distancing themselves from the positions held by the leader of their church. Former Florida Gov. Jeb Bush said: “I don’t get economic policy from my bishops or my cardinals or from my pope. ... I think religion ought to be about making us better as people and less about things that end up getting in the political realm. And former U.S. Sen. Rick Santorum of Pennsylvania said the pope should “leave science to the scientists.”