Results of a study recently published finds raising beef cattle to be ten times more damaging to the environment than chicken, eggs or pork. The US Department of Agriculture, Energy and the Interior analyzed land usage, water consumption, the use of nitrogen fertilizers and the greenhouse gases - like methane coming from the animals digestion and the nitrous oxide from their manure. They simply calculated the resources expended to produce a single calorie from the different food sources.
The results of the 2000 to 2010 study have shown chicken, eggs, pork and dairy to come out about the same, but raising beef cattle is far more inefficient. The animals require 28 times more land, 11 times more water and beef cattle up the carbon footprint with 5 times more greenhouse gases than other agricultural products.
The demand for the red meat continues to climb, especially in the developing world. Another study looked at world wide consumption and estimated the greenhouse gas emissions from all livestock in 237 countries increased by 51% over about the last 50 years. The developed world’s livestock emissions peaked in the 1970‘s and have been in decline ever since - probably due in part to better agricultural practices and in part to reductions in consumption due to health concerns and in part simply vegetarianism for any reason. Unfortunately, that decline is not enough to off-set emissions caused by the increased demands of the developing world. Less meat in the diet is a good idea - especially with world-wide population growth and always more mouths to feed and stomachs to fill.
https://carnegiescience.edu/news/climate_meat_turns_heat
http://thinkprogress.org/climate/2014/07/22/3462537/meat-greenhouse-gases-study-high-emissions-beef/