The very first Earth Day was observed in April of 1970. People were becoming aware of endangered species, air pollution, overpopulation, fuel shortage, pandemics, urban sprawl, and other environmental problems. The danger of nuclear power wasn't new, but it was another concern. The 1970s saw a huge number of science fiction films and images of dystopian futures that asked the question, "What's the worst that could happen?" And while we watched these movies, the underlying message didn't sink in as well as it should have. That could be because they were mostly placed in some far future date, or an undisclosed date we could imagine as far off. Some of those dates have been passed now.
Or maybe you haven't seen them all. Den of Geek compiled a list of nine science fiction films of the 1970s that warned us of how our environmental trends and policies could go very wrong. Back then, they seemed far-fetched, maybe even too far-fetched, or else we would have done more about it. But if you watch them today (and they are available) the dangers they warn of appear much closer to home.