Pope Francis launched the encyclical "Laudato Si', on Care for Our Common Home" on Pentecost Sunday, May 24, 2015. Many people, both inside the Catholic church and in the wider world, consider it to be the most important document published by a pope in the past 120 years.
It is often compared with two other encyclicals: Rerum Novarum, written by Pope Leo XIII in 1891, on capital and labor; and Populorum Progressio, written by Pope Paul VI in 1967, about authentic development. Laudato Si' widens the church's perspective even further because it embraces all creation.
Though Francis uses the teachings of recent popes on ecology, his understanding of what is at stake is quite different from that of his predecessors. In their writings, both Pope John Paul II and Pope Benedict XVI constantly used the term "human ecology" in a way that seemed to emphasize the difference between humans and other creatures.
Francis, in contrast, uses the term "integral ecology" in Laudato Si'. He places human beings right at the heart of creation. He points out, "A good part of our genetic code is shared by many living beings." In the next paragraph, he reminds us, "We are part of nature, included in it."
He adds, "We are not faced with two separate crises, one environmental and the other social, but rather with one complex crisis which is both social and environmental."
Francis is perturbed that "the earth, our home, is beginning to look more and more like and immense pile of filth." He endorses the statement of Ecumenical Patriarch Bartholomew: "For human beings ... to destroy the biological diversity of God's creation; for humans beings to degrade the integrity of the earth by causing changes in its climate, by stripping the earth of its natural forests or destroying wetlands; for human beings to contaminate the earth's waters, its land, its air and its life -- these are sins."