Pope Francis hosted a group of mayors at the Vatican today, including Vancouver's Gregor Robertson.

The meeting focused on how cities can address climate change, sustainability, and poverty.

It comes not long after the pontiff released a Papal Encyclical that emphasized the importance of addressing climate change and caring for the planet.

In the document, he called climate change "a global problem with grave implications", noting that the effects "will be felt for a long time to come, even if stringent measures are taken now".

In addition, Pope Francis addressed the loss of plants and animals, noting that the Bible "has no place for tyrannical anthropocentrism unconcerned for other creatures".

"It is not enough, however, to think of different species merely as potential 'resources' to be exploited, while overlooking the fact that they have value in themselves," Pope Francis wrote. "Each year sees the disappearance of thousands of plant and animal species which we will never know, which our children will never see, because they have been lost for ever. The great majority become extinct for reasons related to human activity."

Robertson stated in a news release that climate change is "the most urgent challenge facing humanity today".

“Pope Francis' leadership will build on the resounding unity of big cities worldwide in calling for meaningful and binding emissions targets, and for a climate agreement signed in Paris that respects the needs of our cities, our planet and generations to come,” the mayor added.