Googlevideo has it online:
SciFi.com has a review that says,
Ironically, the film's most powerful moments do not belong to Heston, who makes a dubious, ambiguous hero. It is Robinson who lays claim to the most moving passages of the film.
StompTokyo says it "is still a powerful film" and that it
walks a fine line between melodramatic Seventies science fiction and a thoughtful examination of problems that began to surface in a decade of oil shortages, endangered species, and Sha Na Na.
Moria's review describes it as "one of the most successful films of its time". 1000 Misspent Hours says that "Together with Silent Running, Soylent Green would make an excellent introduction to early-1970’s polemical sci-fi."