That's a very existential question that doesn't have an easy answer. Is a somewhat brief existence worse than no existence at all? If we eradicate fruit flies (or the many species that live short, brutish existences), have we done them a favor?

I am a huge fan of the Omnivore's Dilemma and recommend it wholeheartedly because while Pollan faces these serious questions, he doesn't simply resort to the easy answer.