Sustainable cities - feasible transition or oxymoron?

In my presentation on Self Sufficiency, Five Years In, I gave some back-of-the-envelope calculations on the carrying capacity of the city of Portland. If everyone in the city does a better job of feeding themselves and fueling their houses from local resources than we expect to manage on our own site, the city could support about 280,000 people. In this best-case scenario, the current population of 600,000 would have to kick out more than half the people to become sustainable.

Leonard emailed me a question about this, and I wanted to post his question and my reply. This illuminates my philosophy of sustainability and what I think it'll really take to adapt to a post peak oil world in a healthy manner.

Leonard asked: "One bit I wanted to question is your assumption about carrying capacity for Portland: it seems to assume that we would need to produce ALL food within city limits, and couldn't rely on a significant portion of land-extensive staple crops being produced on broadacre polycultural farms in our pretty-well-intact horticultural hinterlands. The future that I've envisioned is one in which intensive vegetable gardening for zone 1-3 crops happens in the city, with zone 3-5 crops coming largely from outside using appropriate (low-embodied energy) means of transport into the city."

My reply follows for the rest of this post:

Good question, and thanks for asking it. In short, my calculations
are based on a long term stable, sustainable system. I recognize that
in the short term, the city will have to transition from here to
there. Your model could make sense as a transition strategy.
However, I think any scenario in which a city depends on the
importation of resources perpetuates unsustainability, and a
relationship of domination and exploitation, both of the landbase, and
of the people working it. That is, it doesn't fulfil the "care for
earth" and "care for people" ethics of permaculture. And the "redistribute the surplus" ethic
continues as the current mostly one-way, coerced flow of resources
into the city.

A lot of my thinking is based on Derrick Jensen's writings. I think
his two volume Endgame is the most important reading for modern
times; it gives a crucial analysis of the relationship between cities,
civilization, and our landbases. Should be required reading for all
permaculturists, activists, and anyone else working with the
"invisible structures." You can read an excerpt here of Jensen's Endgame,
talking about cities.

My first concern is that even with the best intentions, when third
parties get between the consumers in the city and the producers
outside the city, the loss of direct connection can quickly lead to
over-harvesting of resources. The middle men have little reason to
foster sustainable harvest, and focus instead on maximum production.
I think this can only be fully averted via direct relationships
between buyers and sellers, complete with buyers being fully educated
about the impacts of harvests on the landbase, and with visits to the
sites of harvest to ensure sustainable operations. Theoretically
feasible, but unlikely to actually happen. (And of course, for
sustainability, you then have to deal with getting the waste products
of the city, such as humanure, back out to the hinterlands.)

My more serious concern is that if a population is dependent on
importing resources, it will use whatever means necessary to keep that
resource coming, including violence. I wonder, in your scenario, what
the incentive is for people outside of the city to provide staple
crops for the city dwellers? Right now the incentives are shiny
gadgetry (cars, electronic toys, and packaged entertainment, and of
course the energy to operate it all) which are made possible by fossil
fuels; and the need to pay property taxes, which boils down to the
threat of violence. (Someone may own their land in the country, but
if they don't pay property taxes, the sheriff with his gun will come
to evict them. Thus they're forced into the cash economy, which often
involves selling off timber, farming the land, etc.)

The only way I see a society acting in a stable, sustainable
relationship with their landbase is when each participant has an
intimate understanding of their landbase and the effects of their
actions on their community of life. That means everyone participating
directly or at most once removed in producing their sustenance.

It's taken me a long time to write this response; I keep going into extensive details and then deleting them. I'm coming from a comprehensive anti-civilization critique, and since I don't know how much exposure you've had to this sort of thought, I'm not sure how much depth to go into to explain my perspective. (Definitely some overlap between anti-civ and permaculture circles, but also plenty of permies who want cities and civilization to keep humming along, just in a kinder gentler sorta way.) I'm happy to write more if you're curious about anything else I said above. But hopefully that gives you an idea of my thoughts...and an understanding of why we're looking to get out of the city and to a landbase which can directly support the people living on it, including us!