Nausicaa of the Valley of the Wind, Spirited Away, and Ponyo, also are all environmentally themed. These were all beautifully animated, I am sure there are a few others that I cannot think of right now.
This 1993 film is about a street kid who develops a special connection to a young Orca whale that was captured and placed in a small tank by the shady owner of a failing amusement park. Caution: some tearjerker scenes with the whale crying to the boy caused my 6-year-old and 8-year-old to cry! "Free Willy" is a must-see for anyone interested in learning about the ethical treatment of animals.