Comparing the environmental impact of dairy production in 1944 to 2007 more

Comparing the environmental impact of dairy production in 1944 to 2007 J. L. Cappera, R. A. Cadyb and D. E. Baumana a b Department of Animal Science, Cornell University, Ithaca, NY, USA Monsanto Company Animal Agricultural Group, St Louis, MO, USA All food production practices have an impact upon the environment, yet the public perception is that historical agriculture was inherently more environmentally sustainable than modern production practices. We evaluated the environmental impact of the 1944 US dairy industry, which produced 53 billion kg milk from 25.6 million cows, compared to that of 2007 (84 billion kg of milk produced by 9.2 million cows). Our stochastic model (Capper et al., PNAS 105: in press) integrated resource inputs and waste outputs from dairy animal nutrition and metabolism, herd population dynamics and crop production to quantify environmental parameters using a life cycle assessment approach. Milk yields, BW, population characteristics, diet ingredients and production practices representative of the pasture-based 1944 system and conventional 2007 system were employed. This novel approach, founded upon NRC nutrient recommendations, allowed system environmental impact to be directly related to productive efficiency of the dairy population. Carbon footprint per cow was 26 kg CO2/d in 2007, compared to 14 kg CO2/d in 1944; however, emphasizing the critical need to evaluate environmental impact on a food production basis, this was equivalent to 3.6 kg CO2/kg milk (1944) vs. 1.3 kg CO2/kg milk (2007). Indexing 2007 to 1.0, the production of one billion kg of milk in the 1944 dairy production system had increased feedstuff, land and water use by factors of 4.5, 16.8 and 2.8, respectively. Furthermore, 2.2-fold increases in N excretion and 3.4-fold increases in P excretion were observed for the 1944 system, which was also associated with considerably higher methane (2.2x) and nitrous oxide (3.3x) emissions per unit of milk produced. Our analysis clearly demonstrates that the considerable improvements in productive efficiency conferred by advances in genetics, nutrition and management have considerably reduced the carbon footprint and mitigated the environmental impact of modern dairy production, thereby improving agricultural sustainability. 1