VATICAN CITY — Pope Francis has instituted a new day of prayer and celebration for the Church entitled the “World Day of Prayer for the Care of Creation,” to be celebrated on Sept. 1 each year.

The day of prayer is in keeping with the theme of the Holy Father’s new environmental encyclical, Laudato Si. It is also seen as a sign of unity with the Orthodox Church, which established Sept. 1 as a day to celebrate creation in 1989.

“The celebration of this 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 and sisters,” Pope Francis said.

He expressed hope that the day could highlight the need for all Christians to work together toward common goals.

“We live at a time when all Christians are faced with the same decisive challenges, to which we must respond together, in order to be more credible and effective,” he said. “It is my hope that this day will in some way also involve other churches and ecclesial communities and be celebrated in union with similar initiatives of the World Council of Churches.”

The day will be an opportunity to reaffirm in Christians their vocation as stewards of God’s creation, to recognize their gratitude for God’s earthly gifts and to pray for the protection of the environment and pardon from sins against it, the Pope said.

Laudato Si was published in June and took its name from St. Francis of Assisi's medieval Italian prayer “Canticle of the Sun.” In it, Pope Francis emphasized the need for a human ecology, which emphasizes the human person as the root motivation for care of the environment.

It is inconsistent, the Pope said in his encyclical, to be concerned about nature without also showing concern for people, especially the poorest and most vulnerable among us, including unborn children.

“Since everything is interrelated, concern for the protection of nature is also incompatible with the justification of abortion. How can we genuinely teach the importance of concern for other vulnerable beings, however troublesome or inconvenient they may be, if we fail to protect a human embryo, even when its presence is uncomfortable and creates difficulties?” (Laudato Si, 120).

On the other hand, Pope Francis reiterated in his institution of the World Day of Prayer for the Care of Creation that the care of the environment needs to be a priority for Christians because of their care for the human person.

“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,” he said, referring to Laudato Si (216).

The Pope expressed his hope that the new day will serve as a call to the faithful to an “ecological conversion,” whereby their encounter with the risen Lord is evident in their care for the world around them.

“We need always to keep in mind that, for believers in Jesus Christ, the Word of God who became man for our sake, ‘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.’” (Laudato Si, 216)

The World Day of Prayer for the Care for Creation is meant to be celebrated “with the participation of the entire people of God: priests, men and women religious and the lay faithful,” Pope Francis said, and it should “become a significant occasion for prayer, reflection, conversion and the adoption of appropriate lifestyles.”