Pope Francis declared September 1 as the World Day of Prayer for the Care of Creation, as the Orthodox Church has done since 1989. You can read the full letter
here.
According to Pope Francis, “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.”
Some options for the liturgy on this day include:
Celebrating the Mass “For the Sanctification of Human Labor” from the Masses and Prayers for Various Needs and Occasions (no. 26; see especially the second Collect of formulary A) may be a fitting option.
This formulary requires the use of Preface V of the Sundays in Ordinary Time, entitled simply “Creation.” The preface speaks eloquently of God’s creation of the world, and the need of humanity to praise God by caring for that creation. Connections between human labor and the care of creation can be drawn out by the formulary itself, and in the homily and Universal Prayer.
Green vestments of that season should be used for the Mass.
Readings may be taken from the appropriate selection in volume IV of the Lectionary for Mass (see Mass “For the Blessing of Human Labor,” nos. 907-911; see especially 907-2 and 909-1).
Even if no special Mass formulary or readings are selected for the occasion, it would still be appropriate to mention the World Day of Prayer for the Care of Creation and its significance in the homily, petitions, and/or concluding announcements.