Help Me Out Here

Having recently finished The Omnivore's Dilemma I'm finding myself in a bit of a quandary. Let me first commend Michael Pollan on writing an excellent book about modern food chains; it could have easily devolved into a touchy-feely polemic about the evils of the modern world, but didn't. Rather, it provides a fairly balanced look at the practices behind modern food production. So kudos to Michael. But I'm digressing... Mr. Pollan makes an excellent case for sustainable agriculture, but acknowleges its limits. As he points out, its not clear that a place like Manhattan could survive on anything other than industrial agriculture. Now it's easy to argue that Manhattan is an overgrown behemoth that survives by siphoning the life from elsewhere (like my property taxes) , one that deserves to collapse under its own weight. But what about other, more reasonably sized cities? Could these cities survive if they were served only by farms practicing sustainable agriculture? While the pursuit of sustainable agriculture is laudable I'm concerned about its implications. If we're to reject industrial agriculture we must, to be consistent, also reject the fruits thereof. From my viewpoint that looks to encompass an awful lot of ground. The increasing efficiency of agriculture is what freed people from tilling the earth and allowed them to pursue other activities, sparking the Industrial revolution and the migration to urban centers. It was from these cities and their associated institutions (businesses, universities, cultural attractions) whence most of what makes life worth living was derived. Not wanting to reject, well, just about everything, it seems to me that we must regard industrial agriculture as a necessary evil. The alternative, adopting sustainable agriculture, would seem to require the gradual dissolution of the cities and all the benefits which they bring. The carrying capacity of sustainably-managed land just isn't high enough to support large concentrations of people. Thus my dilemma: I think Polyface farm is an excellent idea, but I don't want to give up all the benefits of modern development. So, if anyone would care to show me how I can have my cake and eat it too I'd love to hear from you.