Another example of the 'Invisible Green Hand' at work. This time in the dairy industry. See link here.
"The study shows that the carbon footprint for a gallon of milk produced in 2007 was only 37 percent of that produced in 1944. Improved efficiency has enabled the U.S. dairy industry to produce 186 billion pounds of milk from 9.2 million cows in 2007, compared to only 117 billion pounds of milk from 25.6 million cows in 1944. This has resulted in a 41 percent decrease in the total carbon footprint for U.S. milk production."