How can we understand an obligation to the environment?

How can we understand an obligation to the environment?
When taking up the matter of environmental ethics many people affirm that we have a moral obligation to protect the environment. I don’t want to ask if you agree or disagree, but rather if you can make sense of the claim at all. Can we have an obligation to the environment itself, or are we really saying that we have obligations to people (present or future who rely upon the environment)? If we can have a direct obligation to the environment, what is it about an environment that is the proper recipient of that obligation? Is it the animal life in it? Is it the land itself? Do we have the same obligations to all environments (desert and rainforest alike)? If our obligation is really to the people who depend upon the environment, would we be doing anything intrinsically wrong if we destroyed our planet? That is, imagine we developed adequate space travel such that we could find and colonize another suitable planet for all to live on. If every person was safe, prosperous, and consenting on the new planet, would we be doing anything inherently wrong by wringing the last resource out of this planet until every ecosystem was literally destroyed?