I think it's rather silly to claim that the nazis were "environmentalists" in anything like the modern sense. Sure, they had a nature fetish, but surely they were more about lederhosen-clad frolicking in Alpine meadows in a Romantic, homoerotic way? They had no problem with the industrialisation of the Ruhr, did they? I think the autobahns are an admirable feat, but you can hardly class the world's first modern superhighway system as an environmental masterstroke. The whole thesis smacks of gimcrackery if you ask me.
Just found the subtitle: Nature, Environment, and Nation in the Third Reich. The book description says that "the Nazis created nature preserves, championed sustainable forestry, curbed air pollution, and designed the autobahn highway network as a way of bringing Germans closer to nature."
Never mind those millions of exterminated people. :-\