Indeed there are many different kinds of impacts to consider. For instance if you look at CO2 emission per kilo of food, beef emits apparently more than two tim

Indeed there are many different kinds of impacts to consider. For instance if you look at CO2 emission per kilo of food, beef emits apparently more than two times more than farmed salmon and more than four times more than canned tuna (source: http://static.ewg.org/reports/2011/meateaters/pdf/methodology_ewg_meat_eaters_guide_to_health_and_climate_2011.pdf http://static.ewg.org/reports/2011/meateaters/pdf/methodolog...).