This is an answer I just wrote to answer why Pope Francis is big on the environment. It is amazing how my Professor of Social Teaching knew two years in advance that the next social document of the Church would be on the environment.
"And that is because of a greater reason that Pope Benedict advised. He believes that if we don't state strongly about the environment we cannot speak out against destruction of the environment of the human body. This is similar to Pope Leo's document Rerum Novarum at the time of socialism. People thought we needed to stay out of the issue of labor. The Pope said we are losing souls. The issue of the environment is in the line of our Social Teachings since Rerum Novarum. Pope Benedict began to emphasis it. If we dis it we are not helping pro-life issues. I know that students in colleges are being taught that the Church is the reason the environment is being destroyed. I found this out in 1998 after a presentation to college kids."