This movie, about a lone man's quest to save the African elephants from extinction at the hands of big game and ivory hunters, undoubtedly suffered when it was initially released due largely to the fact that it was at least 30 years ahead of it's time. In the 1950s nobody gave a thought to things things like ecology, conservation and endangered species; let alone considered them to be causes worth fighting for. The fact is that, while it would be perfectly natural for modern-day audiences to recognize Morel as a heroic character, in the 1950s he would have been regarded as merely eccentric. That simply goes to show that, while it takes a long time to change peoples' minds, they do change nonetheless.
I understand that Trevor Howard was actually given the role of the central character, Morel, after William Holden dropped out. Frankly, Howard was probably the better choice to play the part in the first place, since he does a good job of keeping the attention of the story grounded where it should be. The film itself is somewhat uneven and episodic, with some interesting character actors making periodic appearances revolving around Morel. Orson Welles, in particular, makes a conspicuous appearance as a larger-than-life American television broadcaster who was probably modeled on Lowell Thomas.
All in all, "The Roots of Heaven" represents a good effort at tackling a subject that probably didn't attract it's initial audience anywhere near as much as it would undoubtedly attract audiences today. Given the change in the public's appreciation of environmentalism, it definitely rates a fresh look by young, contemporary audiences.
