By definition, or the one previous poster is assuming at least, only man can cause pollution. I don't accept that, man is just as much a part of nature as the trees. Still, an undesirable side effect of technology is not the same as something nature does all on her own. (Or mostly, by neglecting the fact that man also affects the growth patterns of the trees).
I agree. The term includes acts of both man and nature. It affects both.