I’ve been thinking about this question, and particularly this part of it
and this additional comment about it
for a good part of the day.
In brief: no and no.
The concept of “stewardship” of the environment (the world that was left to us and we will leave to others) is not exclusive to Christians, who have lately come to recognize our basic responsibilities to others. We are not the only ones aware enough to see this. I’m most familiar (and only a little) with some Native American views, and I think “stewardship” is at least a part of their understanding of responsibility. Honestly, the people I know who are most concerned about good stewardship are not Christians, which is agonizing.
When we recognize our uncontested human ability to alter and harm the environment and the extent to which we do just that, then we must also recognize our responsibility to steward it for the future. That stewardship doesn’t need to involve any kind of faith, but a simple recognition that each of us is only here for a moment of Earth’s history, and has no right to wreck the home that future generations must inhabit. Basic altruism that leads humans to work in community should help us recognize this purpose for the future of all bioforms here and act accordingly.