Nicola (my boss at Heligan) and I went to talk to the people of Portscatho yesterday evening, at one of their Transition Roseland meetings. We did a question and answer session about growing your own veg. "Transition Towns" are an interesting concept. Rob Hopkins's Transition
Handbook considers the issue of Peak Oil and proposes steps communities can take in order to function effectively if/when cheap oil runs out.
Check out http://transitionculture.org and www.transitiontowns.org/Totnes if you're interested. This book is published by Green Books, another site well worth a visit.
An alternative perspective is offered up by Maverick environmentalist and originator of Gaia Theory, James Lovelock. He gives us twenty years.