We depend on the natural world for things. The environment needs saving because if we did make it uninhabitable, it would become very hard for us to live on Earth anymore, which would threaten our species. Also, I think we have a duty to not just let a lot of species go extinct, if we can do something about it we should. It's our responsibility to take care of our planet. We dont know if there is another planet out there suitable to us, Earth is our home, so we must take care of it and save it, including other living creatures that live alongside us.