Much food for thought. I do my best to be as green as possible, catching rainwater in a tank to use for everything except showering and washing clothes and dishes. Reuse and recycle as much as possible etc.
Apart from that, other than through my writing, I will let others, like your friend, do what they are passionate about to physically save the world.
I do feel that writers can do more than their fair share towards saving the world through their words.