I've recently seen Silent Running, a 1972 sci-fi drama starring Bruce Dern as Freeman Lowell, a futuristic park ranger minding Earth's last forests, sealed in gigantic domes aboard an equally gigantic freighter in space.
One thing of note in the movie are the drones, small robots with almost human-like behaviours. This movie pre-dates Star Wars by five years and I wouldn't be at all surprised if George Lucas was inspired by these drones when creating the Star Wars droids, especially R2-D2.
For a movie that is now 37 years old, the ecological message really strikes a chord with the current concern over the global climate. I also see hints of this movie's message in more recent films such as E.T. - The Extra Terrestrial and Wall-E.
I won't go into the plot in great detail, except to say that Lowell must decide how far he is willing to go to protect the last forests of Earth on board the deep space freighter.
I first saw this film as a kid and it left me feeling kind of sad. Watching it again as an adult I'm again left with a haunting feeling of sadness at the conclusion. I am, however, impressed with how the special effects haven't dated as much as I thought they would have.
Interestingly, in an example of life imitating art, a couple of years ago the Svalbard Global Seed Vault was established in an underground cavern on the Norwegian island of Spitsbergen as a secure seedbank to preserve a wide variety of plant seeds from locations worldwide.