(CNN)An environmental campaign group has called on Pope Francis to take up veganism for Lent, in exchange for $1 million donated to the charity of his choice.
Genesis Butler, a 12-year-old US animal rights activist, and the Million Dollar Vegan campaign released an open letter to the Pope, who has made climate change a central concern of his spiritual leadership over the world's 1.2 billion Catholics.
"I write to you today with the utmost respect and appreciation for your speaking out on climate change, habitat loss, and pollution, and for reminding the world that Earth is a home we all share," Butler wrote in the letter, which was published in national newspapers around the world.
Butler cited Pope Francis's 2015 encyclical "Laudato si," in which he called for "changes of lifestyle, production and consumption" to protect the environment. Climate change, he said, "represents one of the principal challenges facing humanity in our day," and will disproportionately affect the world's poorest people.