The environmental impact of dairy cattle continue to be in the news as global warming concerns are raised due to methane production and carbon dioxide relationships. Dairy cows produce methane when digesting feed in the rumen which has 25 times more impact compared to carbon dioxide. While a wide range of claims have been made, 6 percent of the total carbon footprint is from agriculture with dairy responsible for 11 percent of the total 6 percent or 0.7% of the total is related to dairy production. The real story is the huge reducing in the dairy carbon foot print due to the improved efficiency in producing milk. Using 1944 as the base year of comparison (largest number of dairy cows in the U.S.), the number of dairy cows have dropped from 25.6 million cows to 9.2 million cows while milk production increased from 117 billion pounds of milk to 186 billion pounds of milk. Using pounds of carbon dioxide per gallon of milk as the carbon footprint value, it dropped from 31 lb in 1944 to 12 pounds per gallon in 2007. Thus, the dairy industry has become very "green". The National Academy of Science published a peer reviewed paper in 2008 reflecting two strategies in dairy production; the improving of milk production efficiency and impact of organic dairy production to convention production. One challenge is when technology is being denied that improved dairy efficiency (not using GMO application such as crop or rBST). For example if one million U.S. cows produce 10 lb more milk per day due to technology adoption, the following impacts could be expected.

• Reduce 157,000 cows needed to produce the same level of milk
• Reduce 219 fewer hectare of land for feed production
• Reduce methane emission by 41 million kg annually
• Reduce manure excretion by 2.8 million tons annually

Another application was comparing organic milk production to conventional milk production results in needing 25 percent more cows, 30 percent more land for feed production, 39 percent more nitrogen excretion, and 13 percent increase in global warming potential. What does the National Academy of Sciences peer reviewed research results mean to consumers, producers, and the environment.

• For consumers, it requires careful analysis to determine if carbon foot print and global warning applications are more important than denying technology applications, especially when that technology does not change nutrient content of food or impact animal health.
• For dairy managers, increasing milk production efficiency will reduce carbon foot print, nitrogen efficiency, and reduce global warming; these dairy managers are increasingly more "green".

For the environment, using fewer resources to produce food will improve the carbon footprint.