There are lots of reasons to care for the Earth. Here are some. Here are some. Here are some others.
But Tom Rowley, writing at A Rocha, says at the end of the day for Christians one reason should be primary: God.
“For Christians, the primary reason for caring for that which God created is simply because God created it and our doing so brings Him glory.”
Ultimately, God made the Earth and as a work of his hands it bears his image. It speaks of him. It declares his glory, his nature, his power. God himself is working to sustain the Earth and make it flourish every moment. He is committed to it and his delight is set on it.
What God does, the Church must do.