Dear D. Logan,
In deed, the book project "Edible Cities" has a nice history of its own. So, to answer your question I would like to give you some more information about the wider context.
A class of 30 students at Sepp´s Krameterhof had only been holding the Holzer Permaculture Certificate in their hands for a few weeks in 2011, when the renown Austrian publisher "Kneipp-Verlag" approached Judith with the intention to produce a book on urban gardening, and more specifically, on urban permaculture. To cut a long story short, we ended up as intercultural Austro-Germano-Swiss team of authors, each one with his or her specific tasks. Austrian cook and event manager Judith Anger acted as the prime mover and project manager. Swiss-German professional organic gardener Martin Schnyder beautifully mastered the task of writing about recommended edibles, i. e. fruits and vegetables. I myself as a German writer, translator and overall publishing service provider within pharmaceutics, medicine and a healthy lifestile in the widest sense had been in charge of the conceptual design of the book and of about 90 % of the writing and editing task.
The publisher had confronted us with the seemingly unsurmountable challenge of producing the manuscript within just over three months and as would be usual, with only a rather meager budget! Travelling the world to visit all those beautiful projects, in spite of being an appealing thought, was out of the question. At that moment I realised if we had really learnt something at the Krameterhof and about permaculture and if we really believed in what we had learnt, this book should be produced in a "permaculture way", as a joint effort of a team of authors and a larger team of contributors and using easily available technologies. During 2 months we ploughed the web, made use of social networks and communication tools like Skype to identify appropriate projects worldwide, interview their leaders and produce a concise and at the same time a compelling and informative story. Writing happend within three weeks, working Monday to Monday from early morning till late at night. So far the context.
To answer your question, Sepp Holzer had always advocated a broad dissemination of permaculture knowledge, so bringing the concepts of permaculture into the urban area with its high population density seemed like the perfect multiplier at a moment when city farming was becoming a popular concept here in Europe as well and books on urban gardening were sprouting like mushrooms shortly afterwards. To us it seemed only obvious to ask Sepp, having been our main teacher and inspiration, to proofread our manuscript, give us his blessing as the patron and write the preface. It seemed more than appropriate to include him in this "book permaculture". It worked out perfectly I believe.