Earth is all we have. It could be a very long time before we have the technology to live off planet and even then it would take a lot of adjustment. We simply do not have the capability yet and if we destroy the environment before we do, we're toast, that's all there is to it. Also why should other creatures have to suffer because of our actions, they live alongside us on this planet, this planet is the only one we know has this kind of Biodiversity and we do not know if any other planet has this, why should we allow this place to turn into a barren rock? It makes no sense to me at all. The Earth will always be worth saving.