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. (This task is made easier by the coincidence that the day of prayer this year occurs on the day before Labor Day in the United States.)
  • Since it is a Sunday in Ordinary Time, the green vestments of that season should be used for the Mass.
  • The existing readings for the Twenty-Second Sunday in Ordinary Time may be proclaimed, since they are already printed in commonly used participation aids. Nevertheless, some or all of the readings could be replaced by others 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.

RESOURCES:
USCCB (website)
>USCCB Bulletin Insert
Catholic Climate Covenant
>Prayer and Worship Resources

"Holy Hour" for the Care of Creation (Pontifical Council for Justice and Peace)

Creation Justice Ministries
Ignatian Spirituality (Jesuits)
Catholic Agency for Overseas Development (UK)
Catholic Health Association
A Catholic Season of Creation – Sundays of September (Columban Missionaries)

Global Catholic Climate Movement (care should be taken with this site; not all resources are in conformity with the Roman Missal and Catholic liturgical practices)
Season of Creation (Ecumenical)