The global food production sector is growing. In many areas farming systems are intensifying. This rapid growth has in some cases caused environmental damage. This document include an introduction and 12 review papers describing methods for such comparisons as well as the deliberations of their authors, a group of nineteen international experts on environmental economics, energy accounting, material and environmental flows analysis, aquaculture, agriculture and international development. Experts concluded that comparisons can be useful for addressing local development and zoning concerns, global issues of sustainability and trade and consumer preferences for inexpensive food produced in an environmentally sustainable manner. In order to be useful, however, methods to assess environmental costs should be scientifically based, comparable across different sectors, expandable to different scales, inclusive of externalities, practical to implement and easily understood by managers and policy-makers. Aquaculture in many locations and conditions is or could be much more environment friendly than other food sectors.--Publisher's description.