Read blue, go green, as Cameron didn't quite say.
That fact is from this article in the LRB that explains what the Greens are really all about. "The trouble for the Greens is that they really would like to see the end of modern civilisation – as we know it". It's a policy that a lot of people would support. But when I say 'a lot of people' I still mean fewer people than their current poll numbers would suggest.
That interview in Playboy was with Paul Ehrlich, the chap who predicted in 1968 that "In the 1970s and 1980s hundreds of millions of people will starve to death in spite of any crash programmes embarked upon now." As with Malthus, of course, Ehrlich may well have been right except on the question of timing. But just as markets can stay irrational longer than you can stay solvent, I suspect that Western civilisation can stumble on for longer than the Greens can remain the middle-class left's guilt-free alternative to the LibDems.