It just so happens that the green religion is now taking over from the Christian religion. I don't think people have noticed that but it's got all the sort of terms that religions use... The greens use guilt. That just shows how religious greens are. You can't win people round by saying they are guilty for putting (carbon dioxide) in the air.
On the environmental front there's concern about global warming and high levels of carbon dioxide and trees take in CO2 and store carbon.
Great art - or good art - is when you look at it experience it and it stays in your mind. I don't think conceptual art and traditional art are all that different.