In 2015, Pope Francis declared September 1 as the World Day of Prayer for the Care of Creation.  Coinciding with a celebration instituted by the Orthodox Church, it is also a day of ecumenical prayer and unity.
      The Pontifical Council for Justice and Peace (which is in the preocess of merging with the Diastery for Promoting Integral Human Development) has some proposed celebrations on their website.  Gatherings for prayer are encouraged in parishes.  the faithful should also be encouraged to take a practical initiatives to combat earth's enviromental crisis.