Another example of meat-focused research is White T (2000) Diet and distribution of environmental impact, Ecological Economics, vol 34 pp 145-153. This points out that 40% of world grain production is currently fed to livestock. At a global level, animal products make up only about 16% of total calories but generate approximately 35% of total environmental impact from agriculture. The study defines environmental impact in terms of land use. The abstract of the above article may be read here. (This is a pay service.)