David Holmgren is co-originator (with Bill Mollison) of the permaculture concept and author of the recent book, PERMACULTURE: Principles and Pathways Beyond Sustainability. He talks about the need to move beyond the lulling hope that 'green tech' breakthroughs will allow world-wide 'sustainable consumption' to the recognition that dwindling oil supplies inevitably mean a mandatory 'energy descent' for human civilization across the planet. He argues that permaculture principles provide the best guide to a peaceful societal 'powering down."