I think we have to think about sustainability in the broader sense as we might think about our own garden. It is not an answer, not a goal as much as it is a process and a perspective. It is not a solution to be found but a process of maintenance to be continuously tweaked and paid attention to. For about 15 years I measured and recorded everything that went in and out of the different gardens I worked in, and that is certainly part of a useful perspective. A gardener on here raised the issue of what was the real cost of the produce she grew, when all was added up--and that is also a useful perspective. Ravi Shankar was asked why he would spend 20 minutes on stage tuning his instrument, and he answered that he was not really tuning his instrument, he was tuning the audience, bringing them into alignment with what he was about to play. Our gardens tune us and sustain us in many ways. Over the years, I have known many gardeners, farmers, and researchers who started with such fire and did great things, and then burned out--sometimes returning to the "normal world" and sometimes, shifting to become advocates, political activists, writers, and teachers, but in a real way no longer a person of the earth. I am certainly one of these. A while back I went to a yoga retreat by David Williams, the man who brought Pattabhi Jois--in my mind the founder of most of western Yoga--from India to the US. His topic was how to have yoga be part of your life for the rest of your life. He said that two people could do identical yoga routines every day and that watching them, you would not be able to tell any difference. But...one's engine was adrenalin and the chemicals of fight or flight, while the body chemistry engine of the other was more endorphins and the chemicals of the runner's groove. This is the engine that will sustain you. A garden can be a big part of this--of sustaining the gardener by helping them find the groove that will keep them going in the long run. When I was a commercial grower, I had my mental lists of what had to be done by March 1, April 1, May 1, and while I enjoyed the thrill of the ride, I also more or less lived in continuous terror. For months each year, I was only a few days from great and real failure if I could not maintain my frantic pace. So for a food production technology to be sustainable, it must also sustain the gardener in their intimate relationship with nature. Gardens are at one level, anything but natural--you can be as organic at you want, but do not fool yourself, a garden is a huge manipulation of what would be nature were we not there. The trick is to recognize your own creatureness and know that you are part of nature and in an intimate relationship with your garden. So do what matches your life and your body and your need for stimulation, and seek to balance the nature that you are part of. I believe gardens are one of our best interfaces with nature, where we do not just learn and grow things but where we best experience where we should be as creatures within nature.