Several times I have gotten this wrong for putting "He always thinks about the environment" which I would argue that "think of the environment" and "think about the environment" are equivalent (both essentially meaning "think about the consequences to the environment") in this sense. Or am I using a common English expression that is grammatically incorrect?
I think I can sum up the distinction fairly effectively:
Thinking of the environment means that you're taking into account the affect your actions are having on the environment as you act, with the intent of minimizing harm to the environment, or benefiting it.
Thinking about the environment is a more general statement. You're thinking about the environment, but not necessarily for any reason or with any intent.