The reason to be a good environmental steward is to make the earth habitable for ourselves. This is why people who claim “I don’t want kids because of global warming” are so incredibly stupid - the earth does not care a smidgen about them, it’s a rock. If they really cared about the environment they would have as many kids as they could in hopes of raising a great scientist to help the environment!
Another thing to remember is that the earth has been much warmer and much cooler during the time of humanity. We had a little ice age throughout the Middle Ages. While we are most certainly making the earth warmer with technology, this isn’t a death blow to us. We as a species will adapt.
Even if humans had zero output on the environment we would still have to deal with a changing climate - the earth cycles between colder and hotter naturally over time. So becoming better able to heat or cool the earth technologically will be a very good technique for our species.