A Catholic, an Orthodox Christian and an atheist are to present the encyclical Laudato Si, Pope Francis has said. The Pope, speaking during an audience with priests in Rome, said the line-up would reflect the fact that “we need unity to protect creation”. The Pope's encyclical on the environment, entitled Laudato Si, on the care of our common home, will be presented at a press conference in the Vatican's synod hall on Thursday. Yesterday the Pope told pilgrims assembled in St Peter's Square: “I invite you to accompany this event with a renewed attention to the situation of environmental degradation, but also of recovery in one’s own region. "This encyclical is addressed to everyone: let us pray so that all may receive its message and grow in responsibility toward the common home that God has entrusted to us all." "Laudato si" is the introductory phrase to eight verses of St Francis of Assisi's famous prayer thanking God for the gifts of creation. It is medieval Italian, not Latin. "Praised be you, my Lord, with all your creatures, especially Sir Brother Sun, who is the day, and through whom you give us light," one of the first lines says. The prayer also praises God for the gifts of "Sister Moon", "Brother Wind," "Sister Water", "Brother Fire" and "Sister Mother Earth". US Fr Michael Perry, minister general of the Order of Friars Minor, said the canticle was "not just a flowery song about how we should live with nature. It is challenging us to revise our entire way of living our lives" in accordance with Gospel values, he said. "If someone is starving somewhere in the world, we are responsible." The canticle is a call for people to recognise that they are sons and daughters of God and brothers and sisters to one another, he said, "part of one family that embraces all creation: trees, sun, rivers, wind, fire – all of these because they all give glory to God."