In most instances, Church leaders do not have the fortitude to warn the faithful about sexual morality today, so instead they want to latch onto a topic more palatable to the majority left-wing, progressive secular media. And “the environment” is the topic du jour, one the Church can use to seem relevant and “with it” to the world, garnering the admiration of those who otherwise hate the Church and everything she stands for. Furthermore, many in the Church will claim that “the environment,” as such an urgent issue, takes precedence over other matters. This is how they will retain Humanae Vitae on paper, but in practice and a “between-the-lines” manner will implicitly claim there are too many souls on earth. It’ll be a tactic of saying, yes, the Lord wants us to be fruitful and multiply, but we need to clean up our planet first! (btw, Jesus never seemed to mind “overfishing,” as He often intervened to allow the apostles to pull in heaping nets of seafood).