Is beef a factor of pollution?

http://www.amazon.com/Defending-Beef-Case-Sustainable-Production/dp/1603585362

http://www.amazon.com/gp/product/1603584323/ref=pd_lpo_sbs_dp_ss_1/181-4253200-6833161?

http://www.amazon.com/Pasture-Perfect-Choosing-Products-Grass-Fed/dp/0967811619/ref=sr_1_1?

http://www.amazon.com/Eating-Wild-Side-Missing-Optimum/dp/0316227943/ref=pd_bxgy_b_text_y

http://www.wsj.com/articles/actually-raising-beef-is-good-for-the-planet-1419030738