INTRODUCTION

All human activity requires energy. The inescapable minimum is the dietary energy to maintain the population. In earlier times, if one hunter-gatherer could be sure to collect around 33 MJ each day of the year for the family unit (man, woman and two children), then survival of the population was possible. In practice, more organic materials, some with a dietary value, were needed for clothing and shelter. In some cases, there were additional, compulsory contributions to support chiefs, priests, and warriors.

Agriculture provided a way to secure that supply of food and other biological raw materials with less environmental hazard and less competition from other organisms. By its success in raising and stabilizing yields, agriculture has supported an increasing population and released an increasing proportion of it from the persistent chore of food production. With a productive agriculture, societies are more able to participate in the leisure, recreational, cultural, and scientific activities that improve wellbeing. Agricultural productivity has increased per worker and per hectare because the declining number who remain laboring in the field are supported by machines and because inputs of information, improved cultivars, fertilizer, water, and agrochemicals amplify the performance of crop systems.

The development and maintenance of industrialized cultures is based upon the substitution of energy for labor in the non-optional activity of food provision. At the same time, everyone in such cultures, including those who work in agriculture, has developed even greater energy demands for other activities.