Four Japanese researchers have evaluated the impact of Japanese beef production on the environment. I would think that this large impact is partly due to the fat subsidies that the Japanese government lavishes on their agricultural sector. Their study is supported by an American one, Reducing Energy Inputs in the US Food System, by Pimental et al. (Hey, Springer, how 'bout making this article open access?)
But we don't need a study to know that meat has a big environmental impact. Just look at the price! The Christchurch Countdown yesterday had fresh boneless chicken breast on sale for NZ$15/kg, and also dried mung beans for NZ$4.5/kg. Interestingly, the chicken is from right here in Canterbury, while the beans came all the way from Canada. While not perfect, cost is a pretty good indicator of environmental impact.
You will be healthier, live longer, and help save the world if you would eat more wisely. Skip all junk food. Abandon all the chips, crisps, and lollies. Never have a carbonated drink again, nor an "energy" drink, nor bottled water. Schedule your meat intake for 2 to 3 times per week at most. The rest of the time, eat beans, rice, tofu, eggs, corn, whole grain bread, oats, potatoes, lots and lots of vegetables. Asparagus, beets, broccoli, brussel sprouts, cabbage (red is nice), califlower, dandelion (the young leaves), egg plant (I confess I'm not keen on egg plant), fennel, green beans, kale, lima beans, mushrooms, onion, parsley, peas, silver beet (Swiss chard), spinach, zucchini. Seeds are good; sunflower seeds are cheap, fairly low fat (much lower than walnuts) and loaded with vitamin E. Please suggest some more foods!