The Pope made the announcement in a letter released on 6 August in which he said:
Sharing with my beloved brother the Ecumenical Patriarch Bartholomew his concerns for the future of creation (cfr Encylical Letter. Laudato Si, 7-9) and taking up the suggestion by his representative, the Metropolitan Ioannis of Pergamum who took part in the presentation of the Encyclical Laudato Si on the care of our common home, I wish to inform you that I have decided to set up also in the Catholic Church, the “World Day of Prayer for the Care of Creation” which, beginning this year, will be celebrated on the 1st of September, as the Orthodox Church has done for some time now.As Christians we wish to offer our contribution towards overcoming the ecological crisis which humanity is living through. Therefore, first of all we must draw from our rich spiritual heritage the reasons which feed our passion for the care of creation, always remembering that for believers in Jesus Christ, the Word of God who became man for us, “the life of the spirit is not dissociated from the body or from nature or from worldly realities, but lived in and with them, in communion with all that surrounds us.” (ibid., 216). The ecological crisis therefore calls us to a profound spiritual conversion: Christians are called to “an ecological conversion whereby the effects of their encounter with Jesus Christ become evident in their relationship with the world around them.” (ibid., 217). Thus, “living our vocation to be protectors of God’s handiwork is essential to a life of virtue; it is not an optional or a secondary aspect of our Christian experience.”(ibid).The annual World Day of prayer for the Care of Creation offers to individual believers and to the community a precious opportunity to renew our personal participation in this vocation as custodians of creation, raising to God our thanks for the marvellous works that He has entrusted to our care, invoking his help for the protection of creation and his mercy for the sins committed against the world in which we live. The celebration of the Day on the same date as the Orthodox Church will be a valuable opportunity to bear witness to our growing communion with our orthodox brothers. We live in a time where all Christians are faced with identical and important challenges and we must give common replies to these in order to appear more credible and effective. Therefore it is my hope that this Day can involve, in some way, other Churches and ecclesial Communities and be celebrated in union with the initiatives that the World Council of Churches is promoting on this issue.Whilst I look forward to the widest possible cooperation for the best start and development of the World Day of Prayer for the Care of Creation, I invoke the intercession of Mary, the Mother of God and of St. Francis of Assisi, whose Canticle of the Creatures inspires so many men and women of goodwill to live in praise of the Creator and with respect for creation. I support this pledge along with my Apostolic Blessing which I impart with all my heart to you, my dear Cardinals, and to all those who collaborate in your ministry.