There are a lot of intelligent responses here, so naturally I skipped most of them.
Disregard this post if we've covered what I'm about to say.
Is the environment worth saving?
Only until we can transport entire continents and their inhabitants to an exoplanetary body similar to Earth so we can start over and not eff it up this time. As intelligent as we are, we're also incredibly oblivious to wide scale consequences of our mainly industrial progression but our furthering of our knowledge base.
In response to the food-chain topic (Humans > animals)
What happens when we finally shove it and decide "Humans ARE smarter for a reason so we declare ourselves top of the food-chain. Every other animal is inferior and must be slaughtered"?
We eventually run out of meat and end up having to eat genetically engineered beef patties whilst explaining to our grandchildren the now mythical beast, once known as the cow.
Animals are what put us on the top of the food chain. In fact without them, what chain?
This isn't a moral question this is a logic and common sense question.
In regards to morality in general.
Morality is a philosphical stand-point on a matter. It differs in every single existing organism because there is no scientific way of examining morality and wrapping it into a nice little package. Like for example Newton's 3 laws. There will never be 3-laws of morality because there are infinite variables and infinite scenarios to act out these infinite variables with infinite organisms(over time) to manage the infinite variables within infinite scenario's.
When it comes down to it, use your brain. Make a massive pro's and con's list and take into account every variable you can think of. It's why you have that massive chunk of stuff in your skull.