I, too, suspect misrepresentation...
While the professor was probably being deliberately provocative, I'm guessing that his spiel would sound less dire in the lecture hall than it does at ax-grinding second-hand.
Of course, if Professor Pianka actually maintains that the earth is threatened by our affluence and our effluents, he's giving the grand old lady and father time between them far too little credit. Certainly we could bring ourselves down, and a few dozen or so phyla with us, but another ten or twenty million years after the last humans starve to death in the ruins of their cities, an extraterrestrial tourist might not readily detect a trace of us.
cordially,
