These are planes that were going to fly anyway. As another poster said - the only really new thing is the paint scheme. The planes are still owned by the same firms, and still contracted to Amazon for carrying their parcels.
Not to be snarky, but to reduce your environmental impact in this area, you'd have to stop buying things from far away places -- only buying locally produced goods. Which for parts of the world that aren't China, would be hard to do.