This authentic 1970s cult sci-fi classic stars a key figure of the period, patrician hippie Bruce Dern, as an idealistic crew member of a 21st-century space station refusing to destroy the only forest vegetation saved from a defoliated Earth. The screenplay delivers its ecological message with humour and imagination, and Joan Baez sings the appropriate songs. But this deeply moving, immaculately staged film is essentially the work of Douglas Trumbull, only 28 at the time, a special effects expert who got the assignment after making a major contribution to Kubrick’s 2001: A Space Odyssey. — Philip French