The other night I was reading the first issue of the Star Trek Gold Key comic book that was originally published in 1967. In that issue, the crew of the Enterprise finds a distant world where the plants are the dominate lifeform there who consume the animals and not vice-versa. These plants are intelligent, have communities and corral animals in pens like cattle.
However, when the crew of the Enterprise finds out that the plants can release spores into space that could turn any animal they comes into contact with into one of these intelligent plants, Mr. Spock decides to wipe out all life on this world, committing an unimaginable genocide on a global scale, in order to keep the spores from spreading.
It’s interesting that one of the main missions of the Enterprise is to “…seek out new life…” and apparently, according to this comic anyway, obliterate it!*
* Granted, this comic was written by different writers than the series and really plays no part in the official Star Trek history, but still…