There may not have been an Earth Day when artist Harrison Cady created these cartoons, but still he spoke to the subject. These cartoons appeared in Life magazine, in 1925 and 1911, respectively.
Additionally, not by Harrison Cady, but I feel like adding one of my own comics addressing the subject. Art by Doug Rice & Hilary Barta. Appeared in Dark Horse Comics’ Cheval Noir, and the Classics Desecrated album, from NBM.