 If you liked
Push
|
 ...then you might like
Kouchou-sensei to Kujira
|
While Man and Whale is a Greenpeace commercial about saving whales, and Push is a social satire on consumerism and nuclear warfare, essentially both of them are shorts about preserving our planet that come from very talented directors - Koji Yamamura and Osamu Tezuka respectively. So, if you're interested in the topic, check them both.