June 17, 2009

Agriculture's impact on the environment has been receiving much attention, and a recent comparative assessment published by Cornell University researchers has said that the 2007 US dairy system's environmental impact is much lower than that of 1944's dairy system. 

In the 1930-40s, US dairy production was pasture-based with low-input systems with corresponding low output, a sharp contrast to modern high-input, high output systems.

A common perception is that historical methods of food production were more environmentally-friendly than modern practices, but the assessment, which used a deterministic computer model approach and calculates only on-farm effects, has proved that wrong.

All food production systems have an environmental impact, which must be assessed per unit of output.

The 2007 dairy system was modelled according to characteristic production practices of US dairy farms with the total environmental impact based on national milk production and animal numbers. The 2007 US dairy herd had only 9.2 million cows, with an annual milk production of 185.2 billion pounds, while the 1944 US dairy herd totalled 25.6 million cows producing a total of 116.6 billion pounds of milk annually.

Modern dairy practices require only 21 percent of the animals, 23 percent of the feedstuffs, 35 percent of the water and only 10 percent of the land required to produce the same 2.2 billion pounds of milk in 1944, the assessment stated.

Waste outputs were similarly reduced, with modern dairy systems producing only 24 percent of the manure, 43 percent of the methane, and 56 percent of the nitrous oxide per 2.2 billion pounds of milk compared with equivalent milk from historical dairying.

The carbon footprint per 2.2 billion pounds of milk produced in 2007 was 37 percent of equivalent milk production in 1944.

The effect of improved agricultural production efficiency is strengthened by figures from the US Environmental Protection Agency estimating that only 6.4 percent of national green house gas (GHG) emissions arise from agriculture.

Dairy production is only responsible for 11.5 percent of this figure, resulting in a total contribution of less than one percent to US GHG emissions.