When I was in elementary school, I remember seeing a film about a future of Earth in which it was so polluted that everything natural was dead and people had to wear hazmat-like suits and gas masks. But this man lived in a little greenhouse and tended to lots of plants and he didn't have to wear the protective gear inside his greenhouse. Then one day someone discovered the little greenhouse and wanted to get in, but the man refused because if he opened the greenhouse, everything inside would die. Eventually word got out and droves of people came to the greenhouse to try to get in. They ended up breaking the greenhouse and destroying possibly the last living green things on earth. Anyone remember this and know the name of this film? And where I can find it?
I believe this is the short film Ark from 1970. From IMDb:
Set in a near-future Earth where most species are extinct and humans must wear gas masks outdoors... one man (never named in the film) finds a pond with some small breath of life left in it, builds a greenhouse around it...
The reviews also say they used to screen this film in classrooms. The movie is available on Youtube in two parts: Part 1 & Part 2 (where the people with gas masks start breaking into the greenhouse in 5:54).