He helps terraform Mars, and then regrets it

I saw a story on TV when I was a child (in the 80s) that involved a man working from earth to transform the climate of Mars. Then, later, he travels to the surface of Mars, and discovers the corpses of Martian life forms everywhere, which I remember as being made of a lot of squidgy tubes, like octopi or kelp (not humanoid at any rate). He's filled with heartbreak and regret.

I'm pretty sure this isn't from one of the adaptations of The Martian Chronicles.