On Friday, Pope Francis and Patriarch Bartholomew will issue a joint message to mark the World Day of Prayer for the Care of Creation.

During his general audience on Wednesday, Francis appealed for those with influence to “listen to the cry of the earth and the cry of the poor, who suffer most because of the unbalanced ecology.”

The day of prayer was instituted by the Orthodox Church in 1989 by Bartholomew’s predecessor, Patriarch Demetrios I.

In 2015, Bartholomew’s personal envoy, Metropolitan John Zizioulas, was one of the speakers at the presentation of Laudato si’, Francis’s landmark encyclical on environmental ecology. In the document, Francis praised the ecumenical patriarch’s work for the environment.

Zizioulas suggested that all the Christian churches start marking the day together, as an ecumenical gesture.

Francis immediately embraced the idea, and decided to institute the World Day of Prayer for the Care of Creation in the Catholic Church the same year.

In his letter announcing the decision, Francis said the annual commemoration would offer individual believers and communities a fitting opportunity to reaffirm their personal vocation to be stewards of creation, to thank God for the wonderful handiwork which he has entrusted to our care, and to implore his help for the protection of creation as well as his pardon for the sins committed against the world in which we live.

“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,” the pope wrote at the time. “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. 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.”

Since the beginning of his pontificate, Francis has forged a strong bond with Bartholomew. The ecumenical patriarch attended the papal installation, and met with the pope the next year when he visited Jerusalem, where they signed a joint declaration.

Later in 2014, Bartholomew hosted Francis in Istanbul, and the two religious leaders together visited refugees on the Greek island of Lesbos – located off the coast of Turkey – in April 2016. In September 2016, Bartholomew met with Francis in Assisi, for an interfaith peace congress.

In April 2017, Francis, Bartholomew, and Pope Tawadros II – the head of the Coptic Church – prayed together in Cairo, Egypt.

Friday’s message will be the first joint statement marking the day issued by the leaders of the Catholic and Orthodox communions; previously each had issued their own individual statement.

Francis said he and Bartholomew are inviting everyone “to take an attitude of respect and responsibility towards creation.”